Medical device for detecting arrhythmia

Abstract

A medical device is configured to obtain cardiac signal fragments from cardiac signals sensed by sensing circuitry of the medical device, and perform morphological analysis of the cardiac signal fragments for classifying the cardiac signal fragments as one of ventricular tachyarrhythmia, non-ventricular tachyarrhythmia, or cardiac arrest. A medical device may cover a denial rule for suppressing detection of tachyarrhythmia by detecting a ventricular tachyarrhythmia in response to detecting a desired number of tachyarrhythmia intervals when the denial rule is satisfied and a cardiac signal segment is classified as the ventricular tachyarrhythmia based on a morphological analysis.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 492,474, filed March 27, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates in its entirety to medical devices and methods for sensing cardiac signals and detecting arrhythmias. Background Technology

[0003] Medical devices can sense electrophysiological signals from the heart, brain, nerves, muscles, or other tissues. These devices can be implantable, wearable, or external, using implantable and / or surface (skin) electrodes to sense these electrophysiological signals. In some cases, such devices can be configured to deliver treatment based on the sensed electrophysiological signals. For example, implantable or external pacemakers, cardioverter defibrillators, and cardiac monitors sense cardiac electrical signals from a patient's heart. Medical devices can also sense cardiac electrical signals from the chambers of the heart and deliver electrical stimulation therapy to these chambers using electrodes carried by transvenous medical leads that position the electrodes within the patient's heart.

[0004] A pacemaker or cardioverter-defibrillator can deliver therapeutic electrical stimulation to the heart via electrodes carried by one or more medical electrical leads coupled to the medical device. The electrical stimulation may include electrical pulses such as pacing pulses and / or cardioverter-defibrillating shocks. In some cases, the medical device may sense cardiac electrical signals associated with inherent depolarization of the myocardium and control the delivery of stimulation pulses to the heart based on the sensed cardiac electrical signals. Cardiac signals sensed within the heart chambers using endocardial electrodes carried by venous leads, typically having high signal strength and quality, are used to reliably sense cardiac electrical events, such as ventricular R waves sensed from within the ventricles. Upon detection of abnormal rhythms such as bradycardia, tachycardia, or fibrillation, one or more appropriate electrical stimulation pulses may be delivered to restore or maintain a more normal cardiac rhythm. For example, an implantable cardioverter defibrillator (ICD) can deliver a pacing pulse to a patient’s heart when bradycardia or tachycardia is detected, or deliver a cardioverter defibrillator (CV / DF) shock to the heart when tachycardia or fibrillation is detected. Summary of the Invention

[0005] Generally, this disclosure relates to medical devices and techniques for sensing cardiac electrical signals, detecting arrhythmias, and delivering cardiac electrical stimulation therapy as needed. In some examples, the medical device may be coupled to an extracardiac medical lead carrying electrodes positioned outside the heart for sensing cardiac electrical signals and delivering electrical stimulation pulses, including pacing pulses and / or CV / DF shocks. Medical devices operating according to the techniques disclosed herein are configured to perform a global morphological analysis (GMA) of a cardiac signal segment for detecting and / or re-detecting ventricular tachyarrhythmias before and / or after the delivery of electrical stimulation therapy (e.g., CV / DF shock). The cardiac signal segment may have an activation time independent of the timing of sensing ventricular event signals.

[0006] Cardiac signal segments can be classified into tachyarrhythmic segments, non-tachyarrhythmic segments, or cardiac arrest segments based on GMA. When a cardiac signal segment is not classified as a tachyarrhythmic segment (e.g., a non-tachyarrhythmic segment or cardiac arrest segment), the medical device can suppress ventricular tachyarrhythmia detection based on satisfying a rejection rule. The medical device can be configured to perform cardiac signal analysis to determine when a rejection rule for suppressing ventricular tachyarrhythmia detection is satisfied based on evidence of oversensing or evidence of supraventricular tachyarrhythmia (SVT). When a cardiac signal segment is classified as a tachyarrhythmic segment based on GMA, the control circuitry of the medical device can override the rejection rule for suppressing ventricular tachyarrhythmia detection. Ventricular tachyarrhythmia detection is not satisfied when the required number of tachyarrhythmic intervals are detected based on sensed ventricular event signals and the rejection rule is satisfied or overridden because the cardiac signal segment is classified as a tachyarrhythmia based on GMA.

[0007] In one example, this disclosure provides a medical device including sensing circuitry configured to sense a plurality of cardiac signals and to sense ventricular event signals from the cardiac signals. The medical device includes control circuitry communicating with the sensing circuitry. The control circuitry is configured to determine sensed event data from the cardiac signals for each of the plurality of ventricular event signals sensed by the sensing circuitry. The control circuitry is also configured to obtain cardiac signal segments from the plurality of cardiac signals sensed by the sensing circuitry. The cardiac signal segments may have an activation time independent of the timing of the ventricular event signals sensed by the sensing circuitry. The control circuitry may perform morphological analysis of the cardiac signal segments for classifying the cardiac signal segments into one of ventricular tachyarrhythmias, non-ventricular tachyarrhythmias, or cardiac arrest. The control circuitry may determine from the ventricular event signals sensed by the sensing circuitry a desired number of tachyarrhythmia intervals for detecting ventricular tachyarrhythmias. The control circuitry may determine, based on the sensed event data, a rejection rule for suppressing tachyarrhythmia detection. The control circuitry can determine, based on morphological analysis, that a cardiac signal segment is classified as a ventricular tachyarrhythmia. The control circuitry can override a rejection rule for suppressing tachyarrhythmia detection by detecting a ventricular tachyarrhythmia in response to reaching a desired number of tachyarrhythmia intervals and the cardiac signal segment being classified as a ventricular tachyarrhythmia based on morphological analysis. The medical device may also include a treatment delivery circuitry comprising a capacitor. The treatment delivery circuitry can be configured to initiate charging of the capacitor for treatment delivery in response to the control circuitry detecting a ventricular tachyarrhythmia.

[0008] In another example, this disclosure provides a method comprising sensing a plurality of cardiac signals and sensing ventricular event signals from the plurality of cardiac signals. The method may include determining sensed event data from the plurality of cardiac signals for each of the plurality of ventricular event signals sensed by sensing circuitry. The method may also include obtaining cardiac signal segments from the plurality of cardiac signals. The cardiac signal segments may have an activation time independent of the timing of the ventricular event signals sensed by the sensing circuitry. The method may further include performing morphological analysis of the cardiac signal segments to classify the cardiac signal segments into one of ventricular tachyarrhythmias, non-ventricular tachyarrhythmias, or cardiac arrest. The method may include determining from the ventricular event signals a desired number of tachyarrhythmia intervals for detecting ventricular tachyarrhythmias. The method may include determining, based on the sensed event data, that a rejection rule is satisfied for suppressing tachyarrhythmia detection. The method may include determining, based on morphological analysis, that a cardiac signal segment is classified as a ventricular tachyarrhythmia. The method may include overriding a rejection rule for suppressing the detection of tachyarrhythmias by: detecting a ventricular tachyarrhythmia in response to reaching a desired number of tachyarrhythmia intervals and the cardiac signal fragment being classified as a ventricular tachyarrhythmia based on morphological analysis. The method may also include initiating charging of a capacitor for therapeutic delivery in response to the detection of a ventricular tachyarrhythmia.

[0009] In another example, this disclosure provides a non-transitory computer-readable medium storing a set of instructions that, when executed by control circuitry of a medical device, cause the medical device to sense a plurality of cardiac signals and sense ventricular event signals from the plurality of cardiac signals. The instructions may also cause the medical device to determine sensed event data from the plurality of cardiac signals for each of the plurality of ventricular event signals sensed by the sensing circuitry. The instructions may also cause the medical device to obtain cardiac signal segments from the plurality of cardiac signals. The cardiac signal segments may have an activation time independent of the timing of the ventricular event signals sensed by the sensing circuitry. The instructions may also cause the medical device to perform morphological analysis of the cardiac signal segments for classifying the cardiac signal segments into one of ventricular tachyarrhythmias, non-ventricular tachyarrhythmias, or cardiac arrest. The instructions may also cause the medical device to determine from the ventricular event signals a required number of tachyarrhythmia intervals for detecting ventricular tachyarrhythmias. The instructions may also cause the medical device to determine, based on the sensed event data, rejection rules for suppressing tachyarrhythmia detection. The instructions also enable the medical device to determine, based on morphological analysis, that a cardiac signal segment is classified as a ventricular tachyarrhythmia. The instructions further enable the medical device to override rejection rules used to suppress tachyarrhythmia detection by detecting a ventricular tachyarrhythmia in response to reaching a desired number of tachyarrhythmia intervals and the first cardiac signal segment being classified as a ventricular tachyarrhythmia based on morphological analysis. The instructions also enable the medical device to initiate charging of a capacitor for therapeutic delivery in response to the detection of a ventricular tachyarrhythmia.

[0010] In another example, this disclosure provides a medical device including a sensing circuit configured to sense a plurality of cardiac signals and to sense a ventricular event signal from at least one of the plurality of cardiac signals. The medical device includes a control circuit communicating with the sensing circuit. The control circuit is configured to detect ventricular tachyarrhythmias based on the plurality of cardiac signals. After detecting a ventricular tachyarrhythmia, the control circuit can determine, from the ventricular event signal sensed by the sensing circuit, the number of redetections required to reach a tachyarrhythmia interval, and determine, based on analysis of the plurality of cardiac signals, when a rejection rule for suppressing tachyarrhythmia detection is met. The control circuit can also be configured to suppress the redetection of ventricular tachyarrhythmias when the rejection rule is met and the number of redetections required to reach a tachyarrhythmia interval is reached. The control circuit can also be configured to redetect ventricular tachyarrhythmias when a first rejection rule is not met and the number of redetections required to reach a tachyarrhythmia interval is reached.

[0011] In another example, this disclosure provides a method comprising sensing a plurality of cardiac signals and sensing a ventricular event signal from at least one of the plurality of cardiac signals. The method may include detecting a ventricular tachyarrhythmia based on the plurality of cardiac signals. After detecting a ventricular tachyarrhythmia, the method may further include determining from the sensed ventricular event signal the number of redetections required to reach a tachyarrhythmia interval. The method may further include determining, based on analysis, when a rejection rule for suppressing tachyarrhythmia detection is met by the plurality of cardiac signals. The method may further include suppressing the redetection of the ventricular tachyarrhythmia when a first rejection rule is met and the number of redetections required to reach a tachyarrhythmia interval is reached. The method may further include redetecting the ventricular tachyarrhythmia when the first rejection rule is not met and the number of redetections required to reach a tachyarrhythmia interval is reached.

[0012] In this disclosure, a non-transitory computer-readable medium is provided that stores a set of instructions, which, when executed by control circuitry of a medical device, cause another example medical device to sense a plurality of cardiac signals, sense a ventricular event signal from at least one of the plurality of cardiac signals, and detect a ventricular tachyarrhythmia based on the plurality of cardiac signals. The instructions may also cause the medical device, after detecting a ventricular tachyarrhythmia, to determine from the sensed ventricular event signal the number of re-detections required to reach a tachyarrhythmia interval. The instructions may also cause the medical device to determine, based on analysis, when a rejection rule for suppressing tachyarrhythmia detection is met among the plurality of cardiac signals. The instructions may further cause the medical device to suppress re-detection of a ventricular tachyarrhythmia when a first rejection rule is met and the number of re-detections required to reach a tachyarrhythmia interval is reached. The instructions may also cause the medical device to re-detect a ventricular tachyarrhythmia when the first rejection rule is not met and the number of re-detections required to reach a tachyarrhythmia interval is reached.

[0013] The present invention is intended to provide an overview of the subject matter described herein. It is not intended to provide an exclusive or exhaustive interpretation of the devices and methods described in detail in the following drawings and description. Further details of one or more examples are set forth in the following drawings and description. Attached Figure Description

[0014] Figure 1A and Figure 1B This is a conceptual diagram of an example ICD system that can be configured to sense cardiac event signals, detect arrhythmias, and deliver electrical stimulation therapy according to the techniques disclosed herein.

[0015] Figures 2A to 2C Is it implanted in a position with Figures 1A to 1B The diagram shows a concept of a patient with an ICD system arranged in different implantation configurations.

[0016] Figure 3 It is a conceptual diagram based on an example ICD.

[0017] Figure 4 It is based on an example Figure 3 The diagram shows a conceptual illustration of the circuitry that may be included in the sensing circuitry of the ICD.

[0018] Figure 5 This is a conceptual diagram of the tachyarrhythmia operating state of an ICD used to sense and analyze cardiac signals for the detection of ventricular tachyarrhythmias and to deliver treatment in response to the detection of ventricular tachyarrhythmias.

[0019] Figure 6 Is Figure 5 A conceptual diagram of the operations that can be performed by the ICD during irrelevant sensing state 1 of the tachyarrhythmia operating state.

[0020] Figure 7 This is a flowchart of a method, based on some examples, that can be performed by an ICD to select a reliable sensing channel for detecting ventricular tachyarrhythmias.

[0021] Figure 8 It can be executed by ICD for use in Figure 6 A flowchart of a method for detecting insufficient sensing of suspected ventricular tachyarrhythmias during irrelevant sensing state 1.

[0022] Figure 9 This is a flowchart, based on some examples, of a method for performing a general morphological analysis of cardiac signal fragments acquired by an ICD independently of the timing of sensed ventricular event signals.

[0023] Figure 10 This is a flowchart of a method for detecting ventricular tachyarrhythmias, which, according to some examples, can be achieved by combining... Figure 5 The method is performed by ICD 14 during state 2 of the described rapid arrhythmia operating state.

[0024] Figure 11 This is a flowchart, based on some examples, of a method that can be executed by an ICD to determine when a cardiac event oversensing rejection rule for suppressing ventricular tachyarrhythmia detection is met.

[0025] Figure 12 This is a flowchart, based on some examples, of a method that can be executed by an ICD to determine when the SVT rejection rule for suppressing ventricular tachyarrhythmia detection is met.

[0026] Figure 13 Based on some examples, it can be executed by ICD for use in Figure 5The flowchart shows the method for re-detecting ventricular tachyarrhythmias during operation in state 5, which is shown in the diagram.

[0027] Figure 14 This is an illustration of a method for performing a general morphological analysis of cardiac signal fragments during pacing, based on some examples. Detailed Implementation

[0028] Generally, this disclosure describes medical devices and techniques for sensing ventricular event signals (e.g., R waves) and detecting arrhythmias. In various examples, a medical device performing the techniques disclosed herein may be included in an ICD system capable of sensing cardiac electrical signals, detecting arrhythmias based on analysis of the sensed cardiac electrical signals, and delivering electrical stimulation therapy for treating the arrhythmia. In some examples, the ICD is coupled to a cardiovascular external lead. As used herein, the term "cardiovascular external" refers to a location outside the blood vessels surrounding the heart, the heart, and the pericardium. Implantable electrodes carried by the cardiovascular external lead may be positioned extrathoracically (outside the thoracic cavity and sternum) or intrathoracically (below the thoracic cavity or sternum), but generally not in close contact with myocardial tissue, e.g., within the heart or within the pericardium. In other examples, transvenous cardiac external leads may carry implantable electrodes that may be positioned in extrathoracic locations within a vein but outside the heart, e.g., within an internal thoracic vein, jugular vein, or other vein, for sensing cardiac electrical signals and delivering cardiac pacing pulses.

[0029] Figure 1A and Figure 1B This is a conceptual diagram of an example ICD system 10, which can be configured to sense cardiac electrical signals, detect arrhythmias, and deliver electrical stimulation therapy according to the techniques disclosed herein. Figure 1A This is a front view of the ICD system 10 implanted in patient 12. Figure 1B This is a side view of the ICD system 10 implanted in the patient 12. The ICD system 10 includes an ICD 14 connected to an electrical stimulation and sensing lead 16, which is located in an extra-cardiovascular location in this example. Figure 1A and Figure 1B Described within the context of an ICD system 10, which is capable of providing high-voltage CV / DF shocks and / or cardiac pacing pulses in response to the detection of cardiac arrhythmias based on processing of sensed cardiac electrical signals. The techniques for detecting arrhythmias disclosed herein can be implemented in cardiac monitoring devices, which in some examples do not include cardiac pacing and / or CV / DF shock delivery capabilities. Furthermore, the techniques disclosed herein for sensing cardiac electrical signals and detecting arrhythmias can be implemented in a variety of medical devices, including external or implantable cardiac monitors, pacemakers, and ICDs.

[0030] The ICD 14 includes a housing 15 that forms a hermetically sealed enclosure protecting the internal components of the ICD 14. The housing 15 of the ICD 14 may be formed of a conductive material such as titanium or a titanium alloy. The housing 15 may function as an electrode (sometimes referred to as a "can" electrode). The housing 15 can be used as an active can electrode for delivering CV / DF shocks or other high-voltage pulses delivered using high-voltage therapeutic circuitry. In other examples, the housing 15 may be used to deliver unipolar, relatively low-voltage cardiac pacing pulses and / or for sensing cardiac electrical signals in conjunction with electrodes carried by leads 16. In other cases, the housing 15 of the ICD 14 may include multiple electrodes on an outer portion of the housing. The outer portion of the housing 15 that serves as an electrode may be coated with a material such as titanium nitride, for example, to reduce post-stimulation polarization artifacts.

[0031] The ICD 14 includes a connector assembly 17 (also referred to as a connector block or connector) that includes an electrical feedthrough through a housing 15 to provide electrical connection between a conductor extending within the lead body 18 of the lead 16 and electronic components included within the housing 15 of the ICD 14. As will be described in further detail herein, the housing 15 may house one or more processing circuits, memory, transceivers, cardiac electrical signal sensing circuitry, therapeutic delivery circuitry, power supply, and other components for sensing cardiac electrical signals, detecting heart rhythm, and controlling and delivering electrical stimulation pulses to treat abnormal heart rhythms.

[0032] The elongated lead body 18 has a proximal end 27 and a distal portion 25, the proximal end including a lead connector (not shown) configured to connect to an ICD connector assembly 17, and the distal portion including one or more electrodes. Figure 1A and Figure 1B In the example illustrated, the distal portion 25 of the lead body 18 includes defibrillation electrodes 24 and 26 and pacing / sensing electrodes 28 and 30. In some cases, defibrillation electrodes 24 and 26 may form a defibrillation electrode together, as they can be configured to be activated simultaneously. Alternatively, defibrillation electrodes 24 and 26 may form a separate defibrillation electrode, in which case each of electrodes 24 and 26 can be activated independently.

[0033] Electrodes 24 and 26 (and in some examples, housing 15) are referred to herein as “defibrillation electrodes” because they can be used alone or together to deliver high-voltage stimulation therapy (e.g., CV / DF shock). Electrodes 24 and 26 may be elongated coil electrodes and generally have a relatively high surface area for delivering high-voltage electrical stimulation pulses compared to pacing and sensing electrodes 28 and 30. However, in addition to or in lieu of high-voltage stimulation therapy, electrodes 24 and 26, along with housing 15, may also be used to provide pacing functionality, sensing functionality, or both pacing and sensing functionality. In this sense, the use of the term “defibrillation electrode” herein should not be construed as limiting electrodes 24 and 26 to use only in applications of high-voltage CV / DF shock therapy. For example, either electrode 24 or 26 may be used as a sensing electrode in a sensing electrode vector to sense cardiac electrical signals and determine the need for electrical stimulation therapy.

[0034] Electrodes 28 and 30 are relatively small surface area electrodes that can be used in sensing electrode vectors for sensing cardiac electrical signals, and in some configurations can be used to deliver relatively low-voltage pacing pulses. Electrodes 28 and 30 are referred to as pacing / sensing electrodes because they are typically configured for use in low-voltage applications, for example, as cathodes or anodes for delivering pacing pulses and / or sensing cardiac electrical signals, in contrast to delivering high-voltage CV / DF shocks. In some cases, electrodes 28 and 30 may provide pacing functionality only, sensing functionality only, or both.

[0035] The ICD 14 can acquire cardiac electrical signals corresponding to the electrical activity of the heart 8 via a combination of sensing electrode vectors including combinations of electrodes 24, 26, 28, and / or 30. In some examples, the housing 15 of the ICD 14 is used in combination with one or more electrodes from at least one sensing electrode vector, namely electrodes 24, 26, 28, and / or 30. Various sensing electrode vectors utilizing combinations of electrodes 24, 26, 28, and 30 with the housing 15 are described below for sensing one or more cardiac electrical signals. Different sensing electrode vectors can be used to sense each cardiac electrical signal sensed by the ICD 14, and these sensing electrode vectors can be selected by sensing circuitry included in the ICD 14. As described herein, in some examples, the cardiac electrical signals received via the selected sensing electrode vector can be used by the ICD 14 to sense cardiac event signals associated with inherent depolarization of the myocardium, such as R waves associated with ventricular depolarization or, in some cases, P waves associated with atrial depolarization. The sensed cardiac event signals can be used to determine heart rate and the need for cardiac pacing, such as to treat bradycardia or cardiac arrest to prevent long ventricular pauses, or to determine the need for treatment of tachyarrhythmias (e.g., antitachycardia pacing (ATP) or CV / DF shock).

[0036] exist Figure 1A and Figure 1B In the example illustrated herein, electrode 28 is located proximal to defibrillator electrode 24, and electrode 30 is located between defibrillator electrodes 24 and 26. One, two, or more pacing / sensing electrodes may be carried by lead body 18. For example, in some examples, a third pacing / sensing electrode may be located distal to defibrillator electrode 26. Electrodes 28 and 30 are illustrated as loop electrodes; however, electrodes 28 and 30 may comprise any of a variety of different types of electrodes, including loop electrodes, short coil electrodes, hemispherical electrodes, directional electrodes, segmented electrodes, etc. Electrodes 28 and 30 may be positioned along lead body 18 at other locations and are not limited to the locations shown. In other examples, lead 16 may comprise fewer or more pacing / sensing electrodes and / or defibrillator electrodes than in the example shown herein.

[0037] In the example shown, lead 16 extends from connector assembly 27 of ICD 14 toward the center of the patient 12's torso (e.g., toward the xiphoid process 20 of patient 12) and down the thoracic cavity 32 towards the central subcutaneous or submuscular region. Near the xiphoid process 20, lead 16 bends or turns upward, subcutaneously or submuscularly, above the thoracic cavity and / or sternum 22. Although in Figure 1A The lead 16 is illustrated as extending laterally offset from and substantially parallel to the sternum 22, but the distal portion 25 of the lead 16 may be implanted in other locations, such as above the sternum 22, offset to the right or left of the sternum 22, or angled laterally to the left or right of the sternum 22. Alternatively, the lead 16 may be placed along other subcutaneous or submuscular pathways. The path of the cardiovascular lead 16 may depend on the location of the ICD 14, the arrangement and location of the electrodes carried by the lead body 18, and / or other factors. The techniques disclosed herein are not limited to a specific path for the lead 16 or the final location of the electrodes 24, 26, 28, and 30.

[0038] Electrical conductors (not illustrated) extend from a lead connector at the proximal lead end 27 through one or more cavities of the elongated lead body 18 of lead 16 to electrodes 24, 26, 28, and 30 positioned along the distal portion 25 of lead body 18. The elongated electrical conductors contained within lead body 18 (which may be separate, corresponding insulated conductors within lead body 18) are each electrically coupled to the respective defibrillation electrodes 24 and 26 and pacing / sensing electrodes 28 and 30. The respective conductors electrically couple electrodes 24, 26, 28, and 30 to circuitry of ICD 14, such as treatment delivery circuitry and / or sensing circuitry, via connections in connector assembly 17 (including associated electrical feedthroughs through housing 15). The electrical conductors transmit electrical stimulation pulses from the treatment delivery circuitry within the ICD 14 to one or more of the defibrillation electrodes 24 and 26 and / or the pacing / sensing electrodes 28 and 30, and transmit electrical signals generated by the patient's heart 8 from one or more of the defibrillation electrodes 24 and 26 and / or the pacing / sensing electrodes 28 and 30 to the sensing circuitry within the ICD 14.

[0039] The lead body 18 of lead 16 may be formed of a non-conductive material (including silicone, polyurethane, fluoropolymers, mixtures thereof, and / or other suitable materials) and shaped to form one or more cavities in which one or more conductors extend. The lead body 18 may be tubular or cylindrical. In other examples, the distal portion 25 (or all) of the elongated lead body 18 may have a flat, strip, or paddle-like shape. The lead body 18 may be shaped to have a pre-formed distal portion 25, which is typically straight, curved, bent, serpentine, wavy, or serrated.

[0040] In the example shown, the lead body 18 includes a curved distal portion 25 with two "C"-shaped curves, which together may resemble the Greek letter ε. Defibrillation electrodes 24 and 26 are each carried by a portion of one of the two corresponding C-shaped portions of the distal portion 25 of the lead body. The two C-shaped curves extend or bend in the same direction away from the central axis of the lead body 18, along which the pacing / sensing electrodes 28 and 30 are positioned. In some cases, the pacing / sensing electrodes 28 and 30 may be substantially aligned with the central axis of the straight proximal portion of the lead body 18, such that the midpoints of the defibrillation electrodes 24 and 26 are laterally offset from the pacing / sensing electrodes 28 and 30.

[0041] Other examples of cardiovascular external leads that can be implemented using the techniques described herein may include one or more defibrillation electrodes and one or more pacing and sensing electrodes carried by a curved, serpentine, wavy, or zigzag distal portion of the lead body 18. The techniques disclosed herein are not limited to any particular lead body design. In other examples, the lead body 18 is a flexible, elongated lead body without any pre-formed shape, bends, or curves.

[0042] The ICD 14 analyzes cardiac electrical signals received from one or more sensing electrode vectors to monitor aberrant rhythms such as cardiac arrest, bradycardia, ventricular tachycardia (VT), and / or ventricular fibrillation (VF). The ICD 14 can analyze the morphology of heart rate and / or cardiac electrical signals to monitor long pauses (e.g., due to cardiac arrest or bradycardia) and ventricular tachyarrhythmias according to the techniques disclosed herein. The ICD 14 uses a treatment delivery electrode vector, selectable from any of the available electrodes 24, 26, 28, 30, and / or housing 15, to generate and deliver electrical stimulation therapy in response to the detection of a tachyarrhythmia (e.g., VT or VF (VT / VF)). The ICD 14 may deliver ATP in response to VT detection and, in some cases, may deliver ATP prior to a CV / DF shock or during high-voltage capacitor charging to attempt to avoid the need for a CV / DF shock. If ATP fails to terminate VT or when VF is detected, ICD 14 may deliver one or more CV / DF shocks via defibrillation electrodes 24 and 26 and / or housing 15.

[0043] In the absence of a sensed ventricular event signal, such as when a prolonged pause in ventricular activity or cardiac arrest is detected, the ICD 14 can generate and deliver cardiac pacing pulses, such as post-shock pacing pulses or bradycardia pacing pulses. Cardiac pacing pulses can be delivered using a pacing electrode vector comprising one or more electrodes of electrodes 24, 26, 28, and 30 and the housing 15 of the ICD 14.

[0044] As described below, at least one sensing electrode vector can be selected to sense cardiac signal segments within a predetermined time interval to classify the cardiac signal segments into cardiac arrest, non-ventricular tachyarrhythmias, or ventricular tachyarrhythmias based on morphological analysis. Morphological analysis of the cardiac signal segment can be triggered when a prolonged pause in ventricular activity is suspected based on a first analysis of the sensed ventricular event signal according to a bradycardia sensing method. Alternatively, morphological analysis of the cardiac signal segment can be triggered when, according to a tachyarrhythmia sensing method, insufficient sensing of tachyarrhythmias (e.g., insufficient sensing of fibrillation waves or low-amplitude R waves) is suspected based on a second analysis of the sensed ventricular event signal according to a tachyarrhythmia sensing method. In yet another example, morphological analysis can be triggered when the ICD 14 transitions from one tachyarrhythmia operating state to another, for example, as described below. Figure 5 As described.

[0045] When morphological analysis is triggered, cardiac signal segments can be classified as ventricular tachyarrhythmia segments (also referred to herein as “VT / VF segments”), which can cause the ICD 14 to increase its sensitivity for sensing ventricular event signals and suppress ventricular pacing. If the cardiac signal segment is not classified as a VT / VF segment, for example, a non-VT / VF segment or a cardiac arrest segment, this classification can be used to enable ventricular pacing delivery. In some examples, the ICD 14 is configured to detect VT / VF when a rejection rule is not met and the required number of VT / VF intervals have already been detected based on the sensed ventricular event signal. The rejection rule may include criteria applied to the cardiac electrical signals sensed by the ICD 14 to suppress VT / VF detection when oversensitization of P waves, T waves, or non-cardiac noise may occur and / or when SVT may be present, any of which could lead to erroneous VT / VF detection. When a cardiac signal segment is classified as VT / VF, the rejection rule may be ignored or disregarded, such that VT / VF detection is not suppressed even when other criteria used to evaluate the rejection rule are met. When a cardiac signal fragment is not classified as VT / VF based on morphological analysis (e.g., classified as non-VT / VF or cardiac arrest), IMD 14 may suppress the detection of VT / VF if the rejection rule is met even when the required number of VT / VF intervals for VT / VF detection has been counted.

[0046] ICD 14 is shown subcutaneously implanted on the left side of patient 12 along thoracic cavity 32. In some cases, ICD 14 may be implanted between the left posterior axillary line and the left anterior axillary line of patient 12. However, ICD 14 may be implanted in other subcutaneous or submuscular locations in patient 12. For example, ICD 14 may be implanted in a subcutaneous pouch in the pectoral muscle region. In this case, lead 16 may extend subcutaneously or submuscularly from ICD 14 toward the manubrium of sternum 22, and bend or turn downward from the manubrium and extend to the desired subcutaneous or submuscular location. In yet another example, ICD 14 may be placed in the abdomen. Lead 16 may also be implanted in other extravascular locations. For example, as per [reference to...] Figures 2A to 2C As described, the distal portion 25 of the lead 16 can be implanted under the sternum / pleural cavity in the substernal space. Figure 1A and Figure 1B This is illustrative in nature and should not be considered as limiting the practice of the techniques disclosed herein.

[0047] Medical devices operating according to the techniques disclosed herein can be coupled to transvenous or non-transvenous leads, in various examples, for carrying electrodes used to sense cardiac electrical signals and deliver electrical stimulation therapy. For example, a medical device such as the ICD 14 can be coupled to a cardiovascular external lead, as illustrated in the accompanying figures, which refers to a lead that positions the electrodes outside a patient's blood vessels, heart, and the pericardium surrounding the heart. Implantable electrodes carried by a cardiovascular external lead can be positioned extrathoracically (outside the thoracic cavity and sternum), subcutaneously, or submuscularly, or intrathoracically (below the thoracic cavity or sternum, sometimes referred to as a substernal location), and may not necessarily be in close contact with myocardial tissue. Cardiovascular external leads can also be referred to as “non-transvenous” leads.

[0048] In other examples, the medical device may be coupled to a transvenous lead that positions electrodes within a blood vessel, which may be held in an “extracardiac” position outside the heart or advanced to position the electrodes within a cardiac chamber. For example, as an example, the transvenous medical lead may be advanced along a venous pathway to position the electrodes in an extracardiac position within an internal thoracic vein (ITV), intercostal vein, epigastric vein, or azygos vein, hemiazygos vein, or accessory hemiazygos vein. In yet another example, the transvenous lead may be advanced to position the electrodes within the heart, for example, within the cardiac chambers of the atria and / or ventricles.

[0049] exist Figure 1AIn the diagram, external device 40 is shown communicating telemetry with ICD 14 via wireless communication link 42. External device 40 may include processor 52, memory 53, display 54, user interface 56, and telemetry unit 58. Processor 52 controls the operation of the external device and processes data and signals received from ICD 14. Display unit 54, which may include a graphical user interface, displays data and other information to the user to view parameters for ICD operation and programming, as well as cardiac electrical signals retrieved from ICD 14.

[0050] User interface 56 may include a mouse, touchscreen, keypad, etc., to enable users to interact with external device 40 to initiate telemetry sessions with ICD 14 in order to retrieve data from and / or transmit data to ICD 14, including programmable parameters for controlling cardiac event signal sensing, arrhythmia detection, and treatment delivery. Telemetry unit 58 includes a transceiver and antenna configured for bidirectional communication with telemetry circuitry included in ICD 14 and configured to operate in conjunction with processor 52 to send and receive data related to ICD functionality via communication link 42.

[0051] Can be used such as A communication link 42 is established between the ICD 14 and the external device 40 via Wi-Fi, a Medical Implantable Communication Service (MICS), or other radio frequency (RF) links such as RF or communication frequency bandwidth or communication protocols. Data stored or acquired by the ICD 14, including physiological signals or associated data derived therefrom, device diagnostic results, battery status, and the history of detected rhythm episodes and delivered treatments, can be retrieved by the external device 40 from the ICD 14 upon request.

[0052] External device 40 may be embodied as a programmer used in a hospital, clinic, or physician's office to retrieve data from ICD 14 and program the operating parameters and algorithms in ICD 14 to control ICD functions. External device 40 may alternatively be embodied as a home monitor or a handheld device. External device 40 can be used to program cardiac signal sensing parameters, cardiac rhythm detection parameters, and treatment control parameters used by ICD 14. In some examples, external device 40 may be used to program at least some control parameters used in sensing cardiac event signals and detecting arrhythmias according to the techniques disclosed herein, as well as treatment delivery, into ICD 14.

[0053] Figures 2A to 2C Is it implanted in a position with Figures 1A to 1B A conceptual diagram of a patient 12 with different implantation configurations of an extravascular ICD system 10. Figure 2A This is a front view of a patient 12 with an implanted ICD system 10. Figure 2BThis is a side view of patient 12 who has an ICD system 10 implanted. Figure 2C This is a transverse view of a patient 12 with an ICD system 10 implanted. In this arrangement, the cardiovascular external guide 16 of the system 10 is at least partially implanted below the sternum 22 of the patient 12. The guide 16 extends subcutaneously or submuscularly from the ICD 14 toward the xiphoid process 20, and bends or turns within the anterior mediastinum 36 in a substernal position near the xiphoid process 20 and extends upward (see [link to relevant documentation]). Figure 2C ).

[0054] The anterior mediastinum 36 can be considered to be laterally defined by the pleura 39, posteriorly defined by the pericardium 38, and anteriorly defined by the sternum 22 (see [reference]). Figure 2C The distal portion 25 of the guide 16 may extend substantially within the loose connective tissue and / or substernal muscle tissue of the anterior mediastinum 36 along the posterior side of the sternum 22. A guide implanted such that the distal portion 25 is substantially within the anterior mediastinum 36 may be referred to as a “substernal guide”.

[0055] exist Figures 2A to 2C In the illustrated example, lead 16 is positioned substantially below the sternum 22. However, in other cases, lead 16 may be implanted such that it is laterally offset from the center of the sternum 22. In some cases, lead 16 may extend laterally such that, in addition to or in place of the sternum 22, the distal portion 25 of lead 16 is below / below the pleural cavity 32. In other examples, the distal portion 25 of lead 16 may be implanted in other intrathoracic locations outside the heart, including within the pleural cavity or around and adjacent to the pericardium 38 of the heart 8.

[0056] In the various example implantation sites of leads 16 and electrodes 24, 26, 28, and 30 shown and described herein, the cardiac signal sensed by the ICD 14 may have relatively low and / or variable signal strength (e.g., caused by postural changes, breathing, or other body movements) and / or may be contaminated by skeletal muscle electrical activity (SMEA) and / or environmental EMI. Insufficient sensing of R waves or fibrillation waves may result in undetected tachyarrhythmias, which may require ATP or CV / DF therapy. Oversensing of P waves, T waves, SMEA, or other noise may result in false detection of tachyarrhythmias, causing unnecessary ATP or CV / DF shock delivery. In other cases, oversensing of cardiac signals (e.g., missensing P waves or T waves as R waves) or non-cardiac noise (SMEA, EMI, or other electrical noise) may cause pacing pulses to be blocked when cardiac pacing is required to prevent prolonged ventricular pauses or cardiac arrest. Insufficient sensing of R waves or fibrillation waves may result in unnecessary ventricular pacing pulse delivery, which may confuse VT / VF detection. The techniques disclosed herein provide improvements in sensing ventricular event signals (e.g., R waves) and detecting arrhythmias via implantable medical devices. These improvements in sensing and detecting arrhythmias with high sensitivity and specificity can enhance the performance of implantable medical devices in delivering appropriate electrical stimulation therapy to successfully treat detected arrhythmias.

[0057] Figure 3 This is based on a conceptual diagram of an example ICD 14. The electronic circuitry system is enclosed within a housing 15. Figure 3 The ICD (illustrated schematically as an electrode) may include software, firmware, and / or hardware that collaboratively monitor cardiac electrical signals, determine when electrical stimulation therapy is needed, and deliver therapy as needed based on a programmed therapy delivery algorithm and control parameters. The ICD 14 may be coupled to leads, such as lead 16 carrying electrodes 24, 26, 28, and 30, for delivering electrical stimulation pulses to the patient's heart and for sensing cardiac electrical signals.

[0058] The ICD 14 includes control circuitry 80, memory 82, treatment delivery circuitry 84, cardiac electrical signal sensing circuitry 86, and telemetry circuitry 88. A power supply 98 supplies power to the circuitry of the ICD 14 as needed, including each of components 80, 82, 84, 86, and 88. The power supply 98 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. Connections between the power supply 98 and each of the other components 80, 82, 84, 86, and 88 will be made from... Figure 3The overall block diagram is for understanding purposes, but is not shown for clarity. For example, power supply 98 may be coupled to one or more charging circuits included in the treatment delivery circuit 84 for charging holding capacitors included in the treatment delivery circuit 84, which discharge at appropriate times under the control of control circuit 80 to generate electrical pulses according to the treatment protocol. Power supply 98 may also be coupled as needed to components of the cardiac electrical signal sensing circuit 86, such as sensing amplifiers, analog-to-digital converters, switching circuits, etc.

[0059] Figure 3 The circuitry illustrated represents the functionality included in ICD 14 and may include any discrete and / or integrated electronic circuitry components implementing analog and / or digital circuitry capable of producing the functions attributed herein to ICD 14. Functionality associated with one or more circuits may be performed by separate hardware components, firmware components, and / or software components, or integrated within common hardware components, firmware components, and / or software components. For example, cardiac electrical signal sensing and analysis for detecting arrhythmias may be performed collaboratively by sensing circuitry 86 and control circuitry 80, and may include operations implemented in a processor or other signal processing circuitry included in sensing circuitry 86 and / or control circuitry 80, which executes instructions and control signals stored in memory 82, such as blanking intervals and timing periods, and sensing threshold amplitude signals sent from control circuitry 80 to sensing circuitry 86.

[0060] Control circuitry 80 may include hardware configured to execute subroutines of the signal processing and analysis techniques disclosed herein to reduce the processing burden associated with firmware and / or software execution of the processing routines. For example, hardware subroutines (HSRs) may be implemented in control circuitry 80 to perform specific processing functions, such as dedicated mathematical operations, which may include any of the following: sum, absolute value, difference, extrema, histogram counting, signal filtering (e.g., bi-second-order filter, differential filter, or other filter). These HSRs may be invoked by the control circuitry firmware when processing and analyzing cardiac signals to detect arrhythmias, including low-pass filtering, differential filtering, gradient filtering, or other signal processing. HSRs may also be invoked when control circuitry 80 is determining various morphological parameters from cardiac signals to detect arrhythmias as described herein, including any of the following: average time interval, spectral width, low-slope component, signal pulse amplitude, signal pulse interval, etc. These HSRs can reduce the processing burden associated with firmware and / or software processing, thereby reducing current consumption of power supply 98 and extending the lifespan of ICD 14.

[0061] Various circuits of the ICD 14 may include application-specific integrated circuits (ASICs), electronic circuits, (shared, dedicated, or group) processors and memories executing one or more software or firmware programs, combinational logic circuits, state machines, HSRs, or other suitable components or combinations of components that provide the described functionality. The specific form of the software, hardware, and / or firmware used to implement the functionality disclosed herein will be determined primarily by the specific system architecture employed in the ICD and the specific sensing, detection, and therapeutic delivery methods employed by the ICD. Given the disclosure herein, providing software, hardware, and / or firmware to implement the described functionality in the context of any modern medical device system is within the capabilities of those skilled in the art.

[0062] Memory 82 may include any volatile, non-volatile, magnetic, or electrically non-transitory computer-readable storage medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or any other memory device. Furthermore, memory 82 may include a non-transitory computer-readable medium storing instructions that, when executed by one or more processing circuits, cause control circuitry 80 and / or other ICD components to perform various functions belonging to ICD 14 or those ICD components. The non-transitory computer-readable medium storing instructions may include any of the media listed above.

[0063] Control circuitry 80 communicates, for example, via a data bus with treatment delivery circuitry 84 and sensing circuitry 86 to sense cardiac electrical signals, detect cardiac rhythm, and control the delivery of cardiac electrical stimulation therapy in response to the sensed cardiac signals. Treatment delivery circuitry 84 and sensing circuitry 86 may be electrically coupled to electrodes 24, 26, 28, 30 and / or housing 15 carried by leads 16, which may serve as a common or ground electrode or as an active can electrode for delivering CV / DF shock pulses or cardiac pacing pulses.

[0064] A cardiac electrical signal sensing circuit 86 (also referred to herein as "sensing circuit" 86) may be selectively coupled to electrodes 28, 30 and / or housing 15 to monitor the electrical activity of a patient's heart. Sensing circuit 86 may also be selectively coupled to defibrillation electrodes 24 and / or 26 for use in a sensing electrode vector together or in combination with one or more of electrodes 28, 30 and / or housing 15. In some examples, sensing circuit 86 may be enabled to receive cardiac electrical signals from at least one sensing electrode vector selected from available electrodes 24, 26, 28, 30 and housing 15. In some examples, at least two, three or more cardiac electrical signals from two, three or more different sensing electrode vectors may be received simultaneously by sensing circuit 86. Sensing circuit 86 may monitor one or more cardiac electrical signals to sense cardiac event signals, such as R waves accompanying intrinsic ventricular myocardial depolarization. In some examples, sensing circuit 86 may be configured to simultaneously monitor two cardiac electrical signals to sense cardiac event signals. At least one cardiac electrical signal can be received by sensing circuit 86 and transmitted to control circuit 80 for processing and analysis to determine when morphological criteria for detecting arrhythmias are met. As described below, cardiac electrical signals received within a predetermined or specified time interval can be analyzed to classify signal segments as VT / VF, non-VT / VF, or cardiac arrest. In the example shown, sensing circuit 86 may include switching circuitry for selecting which of electrodes 24, 26, 28, 30, and housing 15 are coupled as first sensing electrode vectors to a first sensing channel 83 for receiving a first cardiac electrical signal, which electrodes are coupled as second sensing electrode vectors to a second sensing channel 85 of sensing circuit 86 for receiving a second cardiac electrical signal, and which electrodes are coupled as third sensing electrode vectors to a morphological signal channel 87 for receiving a third cardiac electrical signal.

[0065] When both sensing channels 83 and 85 are included, each sensing channel can be configured to amplify, filter, and digitize cardiac electrical signals received from selected electrodes coupled to the respective sensing channel to improve signal quality for sensing cardiac event signals such as R waves. The cardiac event detection circuitry within sensing circuit 86 may include one or more sensing amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), timers, or other analog and / or digital components, such as in combination. Figure 4 Further described. The cardiac event sensing threshold can be automatically adjusted by each sensing channel 83 and 85 under the control of the control circuit 80, based on sensing threshold control parameters (such as various time periods) and sensing threshold amplitude values ​​that can be determined by the control circuit 80, stored in the memory 82, and / or controlled by the hardware, firmware, and / or software of the control circuit 80 and / or the sensing circuit 86.

[0066] The first sensing channel 83 and the second sensing channel 85 can each control a cardiac event sensing threshold, such as an R-wave sensing threshold, which is applied to incoming cardiac electrical signals to sense cardiac event signals, such as R-waves. When a cardiac event signal is sensed based on exceeding a sensing threshold, the first sensing channel 83 can generate a sensing event signal that is transmitted to the control circuitry 80. For example, when a cardiac electrical signal received via the first sensing electrode vector is detected to exceed the R-wave sensing threshold, the first sensing channel 83 can generate a ventricular sensing event (Vsense) signal that is transmitted to the control circuitry 80. Similarly, when a second cardiac electrical signal received by the second sensing channel 85 is detected to exceed the R-wave sensing threshold, the second sensing channel 85 can generate a Vsense signal that is transmitted to the control circuitry 80. The first sensing channel 83 and the second sensing channel 85 can be configured to automatically adjust the R-wave sensing threshold used by each channel, respectively. The Vsense signals and their relative timing can be used by the control circuitry 80 to determine the sensing event interval for detecting VT / VF and / or controlling pacing pulse delivery.

[0067] The Vsense signal received by the control circuit 80 from the sensing circuit 86 can be used by the control circuit 80 to determine the sensing event interval (referred to herein as the RR interval (RRI)). The RRI is the time interval between two Vsense signals received by the control circuit 80 from the same sensing channel 83 or 85, and may also be referred to as the "intra-channel" sensing event interval. The control circuit 80 may include timing circuitry 90 for determining the RRI between consecutive Vsense signals received from a given sensing channel 83 or 85. In some examples, the control circuit 80 may detect VT / VF based on the RRI. In some cases, the RRI from the pacing pulse to the Vsense signal is determined when a Vsense signal is received after a delivered pacing pulse. Therefore, the RRI may include the time interval between consecutive Vsense signals and the interval between the delivered pacing pulse and the Vsense signal.

[0068] The exemplary techniques disclosed herein are described in conjunction with a sensing circuit 86 configured to receive two distinct cardiac electrical signals via two cardiac event sensing channels 83 and 85 to sense R waves from these two signals, and to receive a third cardiac electrical signal via a morphological signal channel 87 to transmit a digital electrocardiogram (ECG) signal to a control circuit 80 for morphological analysis. The three cardiac electrical signals sensed by the sensing circuit 86 can be received using three distinct sensing electrode vectors selected from available electrodes 24, 26, 28, and 30 and housing 15. In other examples, the sensing circuit 86 may receive two cardiac electrical signals from two distinct sensing electrode vectors, one signal being transmitted to a first sensing channel 83 and the other to a second sensing channel 85. Either or both of these signals may be transmitted as a multi-digit ECG signal to the control circuit 80 for morphological analysis, which analyzes predetermined time segments of the ECG signal to detect cardiac arrest and tachyarrhythmias according to the techniques disclosed herein.

[0069] The timing circuit 90 can be configured to control various timers and / or counters for setting various intervals and windows for sensing ventricular event signals, determining time intervals between received Vsense signals, performing morphological analysis, and controlling the timing of cardiac pacing pulses generated by the treatment delivery circuit 84. The timing circuit 90 can activate timers in response to receiving Vsense signals from sensing channels 83 and 85 to time the RRI between consecutively received Vsense signals within the channels (and in some cases, from the delivered pacing pulse to the Vsense signal). The control circuit 80 can transmit the RRI to the arrhythmia detection circuit 92 to determine and count tachyarrhythmia intervals.

[0070] Control circuit 80 may include arrhythmia detection circuit 92 configured to analyze the RRI received from timing circuit 90 and cardiac electrical signals received from morphological signal channel 87 to detect arrhythmias. Arrhythmia detection circuit 92 may be configured to detect prolonged ventricular pauses (or cardiac arrests) and ventricular tachyarrhythmias based on the sensed cardiac electrical signals meeting corresponding long pause (or cardiac arrest) or tachyarrhythmia detection criteria. For example, control circuit 80 may detect VT / VF when a threshold number of Vsense signals from a sensing channel 83 or 85 each occur with a sensing event interval (RRI) shorter than the tachyarrhythmia detection interval. An RRI shorter than the tachyarrhythmia detection interval may be referred to as a "tachyarrhythmia interval" or "VT / VF interval".

[0071] In some examples, morphological analysis of cardiac electrical signals can be used to confirm or reject rapid arrhythmia detections based on a threshold number of tachyarrhythmia intervals. As further described herein, one or more rejection rules related to possible oversensing of cardiac or non-cardiac events and / or possible SVT can be applied to cardiac electrical signals sensed by sensing circuit 86 to reject VT / VF detections based on a threshold number of VT / VF intervals for VT / VF detection. Arrhythmia detection circuit 92 can perform RRI analysis and cardiac electrical signal analysis to detect or suppress VT / VF detections based on a combination of VT / VF interval counts, morphological analysis of cardiac signal segments, and one or more rejection rules, as further described in conjunction with the accompanying flowcharts and illustrations presented herein.

[0072] The arrhythmia detection circuit 92 may be implemented in the control circuit 80 as hardware, software, and / or firmware to process and analyze signals received from the sensing circuit 86 to detect arrhythmias, including prolonged pauses or cardiac arrest and VT / VF. The arrhythmia detection circuit 92 may identify signal pulses for determining amplitude and / or pulse interval measurements of cardiac electrical signal segments for arrhythmia detection, as further described below. In some examples, the arrhythmia detection circuit 92 may be configured to determine morphological measures of cardiac signal segments related to the signal amplitude, stability, slope component, and / or frequency component of the cardiac signal segment. These morphological measures may be compared to criteria used for detecting prolonged pauses or cardiac arrest or for detecting VT / VF, enabling the treatment delivery circuit 84 to appropriately deliver (or suppress) cardiac pacing and / or CV / DF electrical shock therapy in response to arrhythmia detection.

[0073] In some examples, the arrhythmia detection circuit 92 may include comparators and counters for counting RRIs falling into various rate detection zones, as determined by the timing circuit 90 based on Vsense signals received from sensing channels 83 and / or 85, to determine ventricular rate or perform other rate- or interval-based assessments of the Vsense signals, thereby detecting and distinguishing VT and VF. For example, the arrhythmia detection circuit 92 may compare the RRIs determined by the timing circuit 90 with one or more rapid arrhythmia detection interval zones, such as tachycardia detection interval zones and fibrillation detection interval zones. RRIs falling into detection interval zones may be counted by a corresponding VT interval (VTI) counter or VF interval (VFI) counter, and in some cases, by a combined VT / VF interval counter. For example, the VF detection interval threshold may be set from 300 milliseconds (ms) to 350 ms. For example, if the VF detection interval is set to 320 ms, the VFI counter counts RRIs less than 320 ms. When VT detection is enabled, the VT detection interval can be programmed to be in the range of 350 ms to 420 ms, or programmed to, for example, 400 ms. RRIs shorter than the VT detection interval but greater than or equal to the VF detection interval can be counted by the VTI counter. VT or VF can be detected when the corresponding VT or VFI counter (or the combined VT / VF interval counter) reaches the threshold number of detection intervals (NID) and meets any other VT / VF detection criteria as described herein.

[0074] For example, the NID required to detect VT may require the VTI counter to reach 18, 24, 32, or other selected NIDs. In some examples, the VTI may need to be consecutive intervals, such as 18 out of 18, 24 out of 24, or 32 out of 32, or 100 out of the most recent 100 consecutive RRIs. The NID required to detect VF can be programmed as a threshold number of X VFIs out of Y consecutive RRIs. For example, as an example, the NID required to detect VF could be 18 VFIs out of the most recent 24 consecutive RRIs, 30 VFIs out of 40 consecutive RRIs, or up to 120 VFIs out of 160 consecutive RRIs (or another percentage of a specified number of RRIs). When the VTI or VFI counter reaches the corresponding NID, the arrhythmia detection circuit 92 can detect the ventricular tachyarrhythmia. The NID can be programmable and is not limited to a range from as low as 12 to as high as 120. When VTI or VFI is detected sequentially or discontinuously from a specified number of recent RRIs, the VTI counter or VFI counter reaches the corresponding NID. In some cases, a combined VT / VF interval counter can count both VTI and VFI and detect tachyarrhythmia episodes based on the fastest interval detected when a specified NID is reached.

[0075] The arrhythmia detection circuit 92 can be configured to perform additional signal analysis to determine whether other detection criteria, such as R-wave morphology criteria, episodic criteria, stability criteria, and noise and oversensing rejection criteria, are met before detecting VT or VF based on the achievement of NID. As described below, in some examples, the arrhythmia detection circuit 92 (or generally, control circuit 80) can perform morphological analysis of cardiac signal segments to classify the segments as VT / VF, non-VT / VF, or cardiac arrest. To support these additional analyses, sensing circuit 86 can transmit digitized ECG signals to control circuit 80 (e.g., from morphological signal channel 87) for use in the morphological analysis performed by the arrhythmia detection circuit 92, thereby detecting and differentiating heart rhythms. The cardiac electrical signals received by control circuit 80 from morphological signal channel 87 are referred to herein as “morphological signals.” The cardiac electrical signals received by the morphological signal channel 87 (and / or sensing channels 83 and / or sensing channel 85) may pass through filters and amplifiers, be provided to a multiplexer, and subsequently converted into multi-bit digital signals by an analog-to-digital converter. All of these may be included in the sensing circuitry 86 for storage in memory 82. Memory 82 may include one or more loop buffers to temporarily store segments of digital cardiac signals for analysis performed by control circuitry 80. Control circuitry 80 may be a microprocessor-based controller (which may include an HSR) that employs digital signal analysis techniques to characterize the digitized signals stored in memory 82 to identify and classify the patient's heart rhythm using any of a variety of signal processing methods for analyzing cardiac signals and cardiac event waveforms (e.g., R waves).

[0076] The treatment delivery circuit 84 includes at least one charging circuit 94, which includes one or more charge storage devices, such as one or more high-voltage capacitors for generating high-voltage shock pulses for treating VT / VF. The charging circuit 94 may include one or more low-voltage capacitors for generating relatively low-voltage pulses (e.g., for cardiac pacing therapy). The treatment delivery circuit 84 may include a switching circuit 95 that controls when the charge storage devices discharge across a selected pacing electrode vector or CV / DF shock vector via an output circuit 96.

[0077] In response to the detection of VT / VF, control circuit 80 can schedule treatment and control treatment delivery circuit 84 to generate and deliver treatments, such as ATP and / or CV / DF shocks. Treatment can be generated by initiating charging of a high-voltage capacitor in charging circuit 94. Charging is controlled by control circuit 80, which monitors the voltage on the high-voltage capacitor, which is transmitted to control circuit 80 via a charging control line. When the voltage reaches a predetermined value set by control circuit 80, a logic signal is generated on the entire capacitor line and transmitted to treatment delivery circuit 84, thereby terminating charging. CV / DF shock pulses are delivered to the heart via a control bus through output circuit 96 of treatment delivery circuit 84 under the control of timing circuit 90. Output circuit 96 may include an output capacitor or other output circuit through which the charged high-voltage capacitor discharges via a switching circuit (e.g., an H-bridge) that determines the electrodes for delivering cardioversion or defibrillation pulses and pulse waveforms. Treatment delivery circuit 84 can be configured to receive a signal from external device 40 during ICD implantation or subsequent testing procedures. Figure 1A When programmed, electrical stimulation pulses are delivered to induce rapid arrhythmias (e.g., T-wave impulses or induced pulse trains).

[0078] In some examples, a high-voltage treatment circuit configured to deliver CV / DF shock pulses may be controlled by control circuitry 80 to deliver pacing pulses, for example, for delivering ATP, post-shock pacing pulses, bradycardia pacing pulses, or cardiac arrest pacing pulses. Treatment delivery circuitry 84 may be configured to use a high-voltage capacitor to generate and deliver cardiac pacing pulses, which can be charged to the shock voltage amplitude by charging the high-voltage capacitor to a relatively low voltage corresponding to the cardiac pacing pulse amplitude used to capture and pace the ventricular myocardium. Treatment delivery circuitry 84 may include low-voltage treatment circuitry comprising one or more separate or shared charging circuits, switching circuits, and output circuits for generating and delivering relatively low-voltage pacing pulses for various pacing needs. Treatment delivery circuitry 84 may perform the following operations based on control signals received from control circuitry 80 for delivering cardiac pacing pulses: charging the capacitor to a programmed pulse amplitude and discharging the capacitor for a programmed pulse width. As described above, timing circuit 90 may include various timers or counters that control when cardiac pacing pulses are delivered. The microprocessor of control circuit 80 may set the amplitude, pulse width, polarity, or other characteristics of the cardiac pacing pulses based on programmable values ​​stored in memory 82.

[0079] Control parameters used by control circuit 80 to sense cardiac event signals, detect arrhythmias, and control treatment delivery can be programmed into memory 82 via telemetry circuit 88. Telemetry circuit 88 includes a transceiver and an antenna for communicating with external device 40 using RF communication or other communication protocols as described above. Figure 1A (As shown) Communication. Under the control of the control circuit 80, the telemetry circuit 88 can receive downlink telemetry from the external device 40 and send uplink telemetry to the external device.

[0080] Figure 4 It is based on some examples Figure 3 The diagram illustrates a conceptual design of the circuitry that may be included in the sensing circuitry 86. The sensing circuitry 86 may include a first sensing channel 83, a second sensing channel 85, and a morphological signal channel 87. The first sensing channel 83 and the second sensing channel 85 may each be selectively coupled to a corresponding sensing electrode vector via a switching circuitry included in the sensing circuitry 86, the corresponding sensing electrode vector including at least one electrode carried by a cardiovascular lead 16. The first sensing channel 83 may be coupled to the first sensing electrode vector to receive a first cardiac electrical signal, and the second sensing channel 85 may be coupled to a second sensing electrode vector different from the first sensing electrode vector to receive a second cardiac electrical signal different from the first cardiac electrical signal. In some examples, the first sensing channel 83 may be coupled to a sensing electrode vector that is a short bipolar vector having a relatively shorter interelectrode distance than the sensing electrode vector coupled to the second sensing channel 85 or the morphological signal channel 87. In the example shown, the first sensing channel 83 is coupled to pacing / sensing electrodes 28 and 30 carried by the lead 16. In some examples, the first sensing channel 83 may be coupled to a sensing electrode vector that is approximately vertical (when the patient is in an upright position) or approximately aligned with the heart axis to increase the likelihood of a relatively high R-wave signal amplitude relative to the P-wave signal amplitude. A relatively short inter-electrode distance (e.g., between electrodes 28 and 30 carried by lead 16) may be relatively less susceptible to contamination by skeletal muscle electromyographic noise, EMI, or other non-cardiac noise compared to a relatively long inter-electrode distance, but may have greater variability in R-wave signal intensity compared to a relatively long inter-electrode distance.

[0081] The second sensing channel 85 may be coupled to a second sensing electrode vector, which is a short bipolar or a relatively long bipolar compared to the first sensing electrode vector. The second sensing electrode vector may also be substantially perpendicular to or aligned with the cardiac axis. However, in other examples, the second sensing electrode vector may be orthogonal or transverse relative to the first sensing electrode vector. In the example shown, the second sensing channel 85 is coupled to the pacing / sensing electrode 30 and the housing 15 such that it is a relatively long bipolar, substantially transverse to the sensing electrode vector coupled to the first sensing channel 83. In other examples, the first or second sensing channel may be coupled to either the pacing / sensing electrode 28 or 30 paired with the housing 15, either the pacing / sensing electrode 28 or 30 paired with the coil electrode 24, or either the pacing sensing electrode 28 or 30 paired with the coil electrode 26, provided that at least one electrode between the two sensing electrode vectors is different. In another example, either or both of the first sensing channel 83 or the second sensing channel 85 may be coupled to a sensing electrode vector that does not necessarily include one of the pacing / sensing electrodes 28 or 30. For example, the sensing electrode vector may be coupled to sensing channel 83 or sensing channel 85 that includes one or both of the coil electrodes 24 or 26 and / or housing 15.

[0082] Sensing circuitry 86 may include a morphological signal channel 87 for sensing a third cardiac electrical signal. For example, morphological signal channel 87 may receive a raw cardiac electrical signal from a third sensing electrode vector (e.g., from a vector comprising an electrode 24, 26, 28, or 30 carried by a lead 16 mating with housing 15). In some examples, morphological signal channel 87 may be selectively coupled to a relatively long bipolar pole having an interelectrode distance or spacing greater than that of the sensing electrode vectors coupled to the first sensing channel 83 and / or the second sensing channel 85. The third sensing electrode vector may, but need not, be substantially orthogonal to at least one of the first or second channel sensing electrode vectors. In the illustrated example, coil electrode 24 and housing 15 may be coupled to morphological signal channel 87 to provide the third sensed cardiac electrical signal. The third cardiac electrical signal received by morphological signal channel 87 may be used by control circuitry 80 for morphological analysis for various sensing and arrhythmia detection purposes. For example, control circuit 80 may perform morphological analysis of the signal sensed by morphological signal channel 87 to determine when a morphological-based classification of rapid arrhythmias occurs in a segment of cardiac electrical signal, for use in controlling cardiac pacing, the sensitivity of sensing circuitry for ventricular event signal sensing, VT / VF detection, termination of VT / VF detection, and / or re-detection of VT / VF. In some examples, control circuit 80 may perform waveform morphological matching criteria for verifying the Vsense signal to suppress bradycardia pacing pulses. Various morphological analyses that may be performed by control circuit 80 using the signal received from morphological signal channel 87 are described below in conjunction with the accompanying flowcharts and illustrations presented herein.

[0083] For these purposes, in some examples, the sensing electrode vector coupled to the morphology signal channel 87 may provide a relatively far-field or more global cardiac signal compared to a relatively short bipolar vector that may be coupled to the first sensing channel 83 or the second sensing channel 85. In other examples, any vector selected from available electrodes (e.g., electrodes 24, 26, 28, 30) and / or housing 15 may be included in the sensing electrode vector coupled to the morphology signal channel 87. The sensing electrode vectors coupled to the first sensing channel 83 and the second sensing channel 85, and (at least in some examples) the morphology signal channel 87, may be different sensing electrode vectors that may not have a common electrode, or may have only one common electrode among the different sensing electrode vectors but not two common electrodes. However, in other examples, the sensing electrode vector coupled to one of the first sensing channel 83 or the second sensing channel 85 may be the same sensing electrode vector coupled to the morphology signal channel 87. In this case, sensing channels 83 or 85 and the morphology signal channel 87 may be combined or include shared components such that the morphology signal and the Vsense signal can be output from one sensing channel to the control circuitry 80.

[0084] The first sensing channel 83 and the second sensing channel 85 can each receive cardiac electrical signals to sense ventricular event signals associated with ventricular myocardial depolarization in response to the cardiac electrical signals exceeding the R-wave sensing threshold. The morphological signal channel 87 can receive a third cardiac electrical signal to transmit a multi-digit ECG signal to the control circuit 80 for morphological analysis. Figure 4 In the illustrative example shown, the signals received by the first sensing channel 83, the second sensing channel 85, and the morphological signal channel 87 are provided as differential input signals to pre-filters and preamplifiers 62a, 62b, and 72, respectively. Non-physiological high-frequency and DC signals can be filtered by low-pass or band-pass filters included in each of the pre-filters and preamplifiers 62a, 62b, and 72, and high-voltage signals can be removed by protection diodes included in the pre-filters and preamplifiers 62a, 62b, and 72. The pre-filters and preamplifiers 62a, 62b, and 72 can amplify the pre-filtered signal with a gain between 10 and 100, and in one example, a gain of 17, but each channel can have a different gain and filter bandwidth. The pre-filters and preamplifiers 62a, 62b, and 72 can convert the differential input signals into single-ended output signals that are respectively passed to analog-to-digital converters (ADCs) 63a, 63b, and 73. Pre-filters and pre-amplifiers 62a, 62b and 72 provide anti-aliasing filtering and noise reduction before digitization.

[0085] ADCs 63a, ADC 63b, and ADC 73 convert the first, second, and third cardiac electrical signals from analog signals into digital bitstreams, respectively. As an example, these digital bitstreams can be sampled at 128Hz or 256Hz. ADCs 63a, ADC 63b, and ADC 73 can be Σ-Δ converters (SDCs), but other types of ADCs may also be used. In some examples, the outputs of ADCs 63a, ADC 63b, and ADC 73 can be provided to a decimator (not shown) that acts as a digital low-pass filter, increasing the resolution of the respective cardiac electrical signals and reducing their sampling rate.

[0086] The digital outputs of ADCs 63a, ADC 63b, and ADC 73 are each fed to corresponding filters 64a, 64b, and 74, which may be digital bandpass filters. Bandpass filters 64a, 64b, and 74 may have the same or different bandpass frequencies. For example, filters 64a and 64b may have bandpasses of approximately 10 Hz to 50 Hz, or approximately 13 Hz to 39 Hz, to allow cardiac electrical signals, such as the R wave typically found in this frequency range, to pass through. Filter 74 of the morphological signal channel 87 may have a relatively wide bandpass of approximately 2.5 Hz to 100 Hz. In some examples, each of sensing channels 83, 85, and morphological signal channel 87 may also include notch filters 67a, 67b, and 76, respectively, to filter 50 Hz and 60 Hz noise signals. In some examples, each notch filter 67a, 67b, and 76 may be individually switched on or off.

[0087] The narrowband-pass and notch-filtered signals (if the notch filter is on) in the first sensing channel 83 and the second sensing channel 85 are passed from the corresponding filter 64a or filter 64b (or 67a or 67b) to rectifier 65a or rectifier 65b to generate filtered rectified signals output to the corresponding R-wave detectors 66a and 66b. The first sensing channel 83 includes an R-wave detector 66a for sensing a ventricular event signal in response to a first cardiac electrical signal exceeding an R-wave sensing threshold. In some examples, the second sensing channel 85 includes an R-wave detector 66b for sensing a ventricular event signal in response to a second cardiac electrical signal exceeding an R-wave sensing threshold, which may be controlled separately from the R-wave sensing threshold controlled by the R-wave detector 66a. R-wave detectors 66a and 66b may each include an automatically adjusting sensing amplifier, a comparator, and / or other detection circuitry that compares an incoming filtered and rectified cardiac electrical signal with an R-wave sensing threshold and generates a Vsense signal 68a or 68b when the corresponding first or second cardiac electrical signal exceeds the corresponding R-wave sensing threshold outside the blanking interval after sensing (or pacing).

[0088] The R-wave sensing threshold can be a multi-level sensing threshold, for example, as generally disclosed in U.S. Patent No. 10,252,071 (Cao et al.), which is incorporated herein by reference in its entirety. In simple terms, a multi-level sensing threshold may have an initial sensing threshold that maintains a first fall interval, which may be equal to the tachycardia detection interval or the expected R-wave to T-wave interval; then it decreases to a second sensing threshold that maintains a second fall interval until the end of a second fall interval, which in some examples may be 0.6 seconds to 2.5 seconds long, or in other examples 1 second to 2.5 seconds long, and in one example may be 2.15 seconds (from the Vsense signal). In some examples, the R-wave sensing threshold may decrease in a single stepwise manner to the second sensing threshold. After the second fall interval, the sensing threshold decreases to a minimum sensing threshold, which may be equal to the programmed sensitivity or an increased sensitivity based on morphological analysis of cardiac signal segments. Increased sensitivity can be a sensitivity amplitude setting that is lower than the programmed sensitivity amplitude setting in amplitude (e.g., in millivolts). Sensitivity is also referred to herein as the “sensing floor” because it represents the minimum amplitude of a cardiac electrical signal that can be sensed as a ventricular event signal (e.g., an R-wave or fibrillation wave). In some examples, the R-wave sensing threshold can decrease to the sensing floor in a single step, for example, decreasing to the programmed sensitivity or increasing the sensitivity (an amplitude setting lower than the programmed sensitivity).

[0089] The R-wave sensing thresholds used by R-wave detectors 66a and 66b may each be set to an initial value based on the maximum peak amplitude of the corresponding first or second cardiac electrical signal determined by R-wave detector 66a or 66b during the most recent post-sensing blanking interval. In some examples, the R-wave peak tracking period may be defined as a portion of the post-sensing blanking period during which the maximum peak amplitude is determined. The initial R-wave sensing threshold for each sensing channel 83 and 85 may be reduced over time according to one or more progressively decreasing and / or linear or nonlinear decay rates until a minimum sensing threshold (e.g., equal to the sensitivity setting) is reached, or until the R-wave sensing threshold of the cardiac electrical signal is exceeded. In some cases, the R-wave sensing threshold may be adjusted to the minimum sensing threshold (equal to the sensitivity setting) before the first fall interval expires or before the second fall interval expires, depending on the maximum peak amplitude determined during the R-wave peak tracking period.

[0090] The techniques described herein are not limited to the specific behavior of the sensing threshold or specific R-wave sensing techniques. Instead, other attenuated, progressively adjusted, or otherwise automatically adjusted sensing thresholds can be used to sense ventricular event signals from corresponding first and second cardiac electrical signals. R-wave detectors 66a or 66b can generate Vsense signals 68a or 68b, respectively, in response to the corresponding first or second cardiac electrical signal exceeding the R-wave sensing threshold. Vsense signals 68a or 68b are transmitted to control circuitry 80.

[0091] A broadband-filtered digital cardiac electrical signal 78 output from morphological signal channel 87 can be passed to control circuitry 80 for performing a morphology-based arrhythmia detection method according to the techniques disclosed herein. In some examples, the digital cardiac electrical signal 78 is passed to rectifier 75, and the rectified broadband-filtered signal 79 is passed to control circuitry 80 for processing and analysis. In some cases, both the filtered unrectified signal 78 and the rectified signal 79 are passed from morphological signal channel 87 to control circuitry 80 for determining the morphological characteristics of the ECG signal. As described below, an n-second ECG signal segment can be buffered in memory 82 by control circuitry 80 for processing and analysis to classify the segment into, for example, cardiac arrest, VT / VF, or non-VT / VF. The n-second ECG signal segment analyzed by arrhythmia detection circuitry 92 may undergo additional low-pass, band-pass, and / or high-pass filtering and / or other signal processing prior to analysis to determine the morphological or other characteristics of the ECG signal segment for arrhythmia detection.

[0092] like Figure 4 The configuration of sensing channels 83 and 85 and morphological signal channel 87 shown is illustrative in nature and should not be considered as a limitation of the techniques described herein. Sensing circuitry 86 may include... Figure 4 The illustrated and described components may include more or fewer components, and some components may be shared between sensing channels 83 and 85 and morphological signal channel 87. For example, a common cardiac electrical signal from a selected sensing electrode vector may be received by a pre-filter and pre-amplifier circuit and an ADC, and then passed to a narrowband filter in one of sensing channels 83 or 85 and a wideband filter in morphological signal channel 87. In other examples, sensing circuit 86 may include or exclude one or more sensing channels, each configured to generate a Vsense signal, and / or more than one morphological signal channel. In other examples, a wideband filtered morphological signal may be passed from one of sensing channels 83 or 85 to control circuitry 80 for performing analysis of cardiac signal segments for detecting arrhythmias according to the techniques disclosed herein. Furthermore, components for filtering, amplification, digitization, rectification, etc., may be shared with... Figure 4 Different sequences or combinations are shown for arrangement.

[0093] Figure 5 This is a conceptual diagram 100 of the tachyarrhythmia operating state of an ICD 14, based on some examples, related to a method performed by the ICD 14 for sensing and analyzing cardiac signals to detect VT / VF and delivering treatment in response to VT / VF detection. At block 102, the ICD 14 operates in an unrelated sensing state 1 (also referred to herein as "unrelated state 1" or simply "state 1"). During unrelated sensing state 1, control circuitry 80 receives a Vsense signal from sensing circuitry 86 and determines the RRI according to the tachyarrhythmia sensing method. In some examples, the Vsense signal is received from each of sensing channels 83 and 85. Each sensing channel 83 and 85 may be initially sensing ventricular event signals according to a programmed sensitivity for each sensing channel, which may be a user-programmed or default sensitivity setting and is referred to hereinafter as "programmed sensitivity".

[0094] The control circuit 80 determines the RRI between consecutively received Vsense signals in each sensing channel 83 and 85. The RRI is compared to the VT detection interval region or threshold (when VT detection is enabled) and / or the VF detection interval region or threshold interval to identify VTI and / or VFI. When the RRI is determined to be VTI or VFI, a corresponding VTI counter or VFI counter (and / or a combined VT / VF interval counter) is specified for incrementing to count the VTI and VFI identified for the respective sensing channel 83 or 85. Therefore, each sensing channel 83 and 85 may be associated with a VTI counter, a VFI counter, and / or a combined VT / VF interval counter. The VTI counter, VFI counter, and combined VT / VF interval counter (if used) are also collectively referred to herein as the VTI / VFI counter. However, it should be recognized that in some examples, VT detection may not be enabled in the ICD 14, making only the VFI counter available to track the VFI for each sensing channel 83 and 85.

[0095] When the VTI or VFI counter of at least one sensing channel 83 or 85 reaches the NID required for VT or VF detection, ICD 14 may transition (as indicated by arrow 103a) to the relevant tachyarrhythmia detection state 2 in block 104. When sensing circuitry 86 sets the sensing ventricular event signal according to the programmed sensitivity of each sensing channel 83 and / or 85, ICD 14 may transition to the relevant tachyarrhythmia probable state 2 in block 104 in response to reaching the NID, also referred to herein as "relevant state 2" or simply "state 2". As described below, when sensing channel 83 or 85 satisfies the NID, in order to transition to the relevant tachyarrhythmia detection state 2, control circuitry 80 may identify a sensing channel 83 or 85 as a reliable sensing channel for VT / VF detection. The sensing channel 83 or 85 selected as a reliable sensing channel may require reaching the NID (via the associated VTI / VFI counter) in order to transition from state 1 in block 102 to state 2 in block 104. If sensing channel 83 or 85, identified as a reliable sensing channel for detecting VT / VF, is not a sensing channel associated with a VTI / VFI counter that has reached NID, then control circuitry 80 may remain in the unrelated sensing state 1 of block 102. Control circuitry 80 may perform a method during unrelated sensing state 1 to sense ventricular event signals using both sensing channels 83 and 85 and determine when criteria for transitioning to the relevant state 2 of block 104 are met, as generally disclosed in U.S. Patent Application No. 17 / 823,055 (Liu et al.), filed August 28, 2022.

[0096] As further described below, during irrelevant state 1, control circuit 80 may enable Global Morphological Analysis (GMA) of cardiac signal segments. As used herein, “Global Morphological Analysis” or “GMA” refers to the analysis of cardiac signal segments performed by control circuit 80, which can begin and end independently of the timing relationship with Vsense signals received from sensing circuit 86. Cardiac signal segments undergoing GMA may have a duration greater than the total duration of multiple VT detection intervals or multiple VF detection intervals. Therefore, the classification of cardiac signal segments based on GMA is independent of the timing, rate, or interval between Vsense signals. Thus, compared to VT / VF detection based solely on rate or interval, the classification of cardiac signal segments based on GMA can be relatively unaffected by or independent of the confounding factors of oversensing of ventricular event signals or the presence of SVT. By performing GMA, VT / VF detection and the differentiation between the occurrence of true VT / VF and the occurrence of oversensing and SVT can be improved.

[0097] During GMA execution, control circuitry 80 determines at least one characteristic of sampling points of the cardiac signal segment without using or relying on the timing of any R-waves, fibrillation waves, or sensing event signals within the cardiac signal segment. For example, the analysis may use sampling points spanning the entire cardiac signal segment with sampling intervals to determine morphological metrics. The analysis may determine at least one metric associated with the frequency component of the cardiac signal segment. The analysis may include determining metrics associated with the slope component of the cardiac signal segment. In some examples, the analysis may include determining metrics associated with the amplitude and / or noise component of the cardiac signal segment.

[0098] In some examples, when GMA is enabled during irrelevant sensing state 1 and the first cardiac signal segment being analyzed is classified as VT / VF, control circuitry 80 may continue GMA for one or more subsequent cardiac signal segments. When a threshold number of cardiac signal segments are classified as VT / VF based on GMA and the VTI and / or VFI counts tend upward toward NID but have not yet reached NID, control circuitry 80 may transition from state 1 to state 2 (as indicated by arrow 103b). For example, to cause a transition to state 2 as indicated by transitioning to block 104 via arrow 103b, when at least two, three, or other specified number of cardiac signal segments are classified as VT / VF based on GMA, the VTI / VFI counts may need to be greater than a threshold of 50%, 60%, 70%, 80%, or 90% of NID, but may be less than NID.

[0099] In other cases, when at least one cardiac signal segment is classified as VT / VF based on the GMA of the cardiac signal segment, control circuit 80 may increase the sensitivity of sensing channels 83 and 85 for sensing ventricular event signals during the irrelevant sensing state 1 of block 102. NID may be reached after increasing the sensitivity of sensing channels 83 and / or 85 to make them more sensitive to sensing low-amplitude R waves and / or fibrillation waves. When NID is reached after increasing sensitivity, control circuit 80 may transition to the relevant state 2 of block 104 (arrow 103a).

[0100] In various examples, control circuitry 80 can be configured to perform GMA to classify cardiac signal segments, for example, as described below. Figure 9As described, and based on the Vsense signal received from sensing circuit 86, the RRI is determined for counting the VT / VF interval to determine when the criteria for transitioning from irrelevant state 1 (box 102) to relevant state 2 (box 104) are met. For example, in other examples, ICD 14 may transition to relevant state 2 at box 104 when a threshold number of cardiac signal segments out of Y consecutive cardiac signal segments are classified as VT / VF (in some examples, where X may equal Y). For example, control circuit 80 may transition to relevant state 2 at box 104 when at least two consecutive, two out of three, three consecutive, three out of four, or other selected number of recent cardiac signal segments are classified as VT / VF.

[0101] The criteria for transitioning from an unrelated sensing state 1 in box 102 to a relevant state 2 in box 104 based on a threshold number of cardiac signal segments classified as VT / VF according to GMA may include a threshold VTI / VFI count that may be less than NID (but greater than zero). For example, when at least one cardiac signal segment is classified as VT / VF based on GMA, a VTI / VFI count of at least 3, 5, 8, 10, or 20, or other selected thresholds, may be required for transitioning to relevant state 2 in box 104. In yet another example, multiple conditions may be defined for transitioning from an unrelated sensing state 1 in box 102 to relevant state 2 in box 104, including different threshold numbers of GMA-classified VT / VF segments paired with different thresholds for the VT / VFI count. For example, if a relatively high number of cardiac signal segments are classified as VT / VF based on GMA, such as two out of two or three out of three, a relatively low threshold VTI / VFI interval counter may be required, such as 10 VT / VF intervals out of 30 RRIs. If a relatively low number of cardiac signal segments are classified as VT / VF based on GMA, such as one of three, a relatively high threshold VTI / VFI count may be required, such as 20 out of 30 RRIs. In some examples, a threshold number of cardiac signal segments classified as VT / VF based on GMA can cause a transition from unrelated sensing state 1 to relevant sensing state 2 when all VTI / VFI counts are zero. For example, if three, four, or other threshold numbers of consecutive signal segments are classified as VT / VF based on GMA, control circuitry 80 can transition to relevant sensing state 2. Therefore, multiple state transition conditions can be defined, including one or more combinations of reaching NID, a threshold number of GMA-based VT / VF cardiac signal segments, and / or a threshold number of GMA-based VT / VF cardiac signal segments and scaled VTI / VFI count values. When any one of the state transition conditions is met, control circuitry 80 can transition from unrelated sensing state 1 of block 102 to relevant state 2 of block 104. The following is in conjunction with Figure 6Aspects of the operation of ICD 14 in the rapid arrhythmia operating state of box 102 (i.e., the unrelated sensing state 1 of box 102) are described.

[0102] It should be understood that the transition from state 1 in box 102 to state 2 in box 104 may not represent a VT / VF detection that will result in the scheduling or initiation of ATP and / or CV / DF shock therapy. During state 2 of the relevant tachyarrhythmia detection in box 104, control circuit 80 may suspect that a VT / VF episode may be occurring based on the attainment of NID and / or the satisfaction of other criteria, thus causing a transition to state 2. However, while operating in the relevant state 2, control circuit 80 may determine whether all criteria for VT / VF detection are met. For example, control circuit 80 may determine whether any VT / VF rejection rules are met. A VT / VF rejection rule is met when processing and analysis of the cardiac electrical signals sensed by sensing circuit 86 indicates that NID may be reached due to SVT, oversensing of cardiac events such as P waves or T waves being incorrectly sensed as R waves, or oversensing of non-cardiac noise being incorrectly sensed as R waves. Based on the VT / VF rejection rule analysis of the sensed cardiac electrical signals, when the probability or likelihood of reaching NID due to actual VT / VF is uncertain or reduced, the VT / VF rejection rule is applied to suppress VT / VF detection. If the VT / VF rejection rule (also referred to as the "rejection rule") is not met and the NID for VT / VF detection is met, the control circuit 80 can transition to charging state 3 of block 106. VT / VF can then be detected based on reaching NID and not meeting the VT / VF rejection rule.

[0103] As further described below, when applying a rejection rule to suppress VT / VF detection when NID is met, control circuit 80 may also require that the cardiac signal segment not be classified as a VT / VF segment based on GMA. When the cardiac signal segment is classified as a VT / VF segment, the satisfied rejection rule can be overridden by the GMA-based VT / VF classification of the cardiac signal segment, so that VT / VF detection is not suppressed based on the rejection rule. In some examples, the GMA result of the VT / VF classification of the cardiac signal segment can prevent the rejection rule from being satisfied. In either case, when NID is met, the GMA result of VT / VF can override the suppression of VT / VF detection based on the rejection rule.

[0104] If it is determined that the VT / VF rejection rule is met during relevant state 2 of box 104 and the VT / VF rejection rule is not covered by the VT / VF classification of the cardiac signal fragment based on GMA, then ICD 14 may suppress the detection of a suspected VT / VF episode and remain in relevant state 2 of box 104 until the VT / VF rejection rule is not met based on further analysis of the cardiac signal sensed by sensing circuit 86. The following example combines... Figure 11 The flowchart describes the method performed by the ICD control circuitry during the relevant tachyarrhythmia operation state 2 in block 104. When VT / VF is detected based on satisfying the NID when the VT / VF rejection rule is not met, the control circuitry 80 may subsequently transition to the charging state 3 in block 106. During the charging state 3 in block 106, the treatment delivery circuitry 84 may begin charging the high-voltage capacitor under the control of the control circuitry 80 to prepare for the delivery of CV / DF shocks. If the cardiac signal fragment is buffered or processed according to GMA after transitioning to charging state 3, the buffering or processing according to GMA may continue without interruption, such that the GMA results can be used to determine if the treatment discontinuation criteria are met, and / or if the treatment discontinuation criteria are met, the GMA results can be used to re-detect VT / VF in re-detection state 5, as described below.

[0105] However, in some cases, when operating in state 2 of box 104, control circuit 80 may determine whether termination criteria are met based on analysis of the cardiac electrical signals sensed by sensing circuit 86 before all VT / VF detection criteria are met during the relevant state 2 of box 104 (e.g., NID is met when all VT / VF rejection rules are not met). Examples of termination criteria may include requiring a threshold number of cardiac signal segments to be classified as non-VT / VF or cardiac arrest (non-VT / VF) based on GMA. Other termination criteria may be based on a median RRI greater than a threshold interval, determined according to the Vsense signal received from sensing circuit 86. Other termination criteria may include detecting one or more normal sinus rhythm events based on RRI and R-wave morphology matching, which may cause the VTI / VFI counter to be reset to, for example, zero or a value lower than the current counter value.

[0106] In another example, termination can be detected by control circuitry 80 during the relevant sensing state of block 104 when the number of RRIs (e.g., 6, 8, 10, 12, or other specified numbers) is greater than a slow interval threshold. The slow interval threshold can be set based on a VT detection interval threshold or a VF detection interval threshold (e.g., an offset or percentage longer than the VT / VF detection interval threshold). The slow interval threshold can be determined based on the detected rhythm cycle length (RCL). For example, RCL can be determined as the mean or median of a specified number of recent RRIs counted as VT / VF intervals, e.g., just before reaching NID. RCL can be calculated by control circuitry 80 as a truncated mean, e.g., by determining the average RRI after removing the shortest and / or longest RRIs (up to the point where NID is met) from the most recent N RRIs. In one example, if eight RRIs following the NID are longer than the RCL plus an offset (e.g., plus 40ms, 50ms, 60ms, 70ms, or 80ms), control circuitry 80 can detect termination. Various methods can be implemented to determine if a suspected or detected VT / VF episode has terminated before treatment delivery. Control circuitry 80 can transition from relevant state 2 of block 104 back to indifferent sensing state 1 of block 102 in response to meeting termination criteria. Upon returning to indifferent sensing state 1, control circuitry 206 can reset the VTI / VFI counter to zero.

[0107] During the charging state 3 of block 106, control circuit 80 may determine whether treatment discontinuation criteria are met based on analysis of cardiac electrical signals sensed by sensing circuit 86. Control circuit 80 may discontinue CV / DF shocks prior to delivery when 60%, 70%, 80%, or other threshold numbers of RRIs are longer than the slow interval threshold. For example, control circuit 80 may discontinue CV / DF shock therapy if four of the five most recent RRIs are at least 60 ms longer than the RCL (or other offset). In another example, treatment discontinuation criteria are met when at least four of the five most recent RRIs are equal to or greater than the VF detection interval threshold plus an offset (e.g., 60 ms). In some examples, the slow interval threshold is RCL plus 60 ms when VT is detected. When the detected tachyarrhythmia is tachyarrhythmia (fast VT) or VF, the slow interval threshold may be the VF detection interval threshold plus 60 ms or RCL plus 60 ms, whichever is greater. However, in some examples, when the difference between the minimum and maximum RRI used to calculate RCL is greater than a threshold difference (e.g., greater than 50 ms), the slow interval threshold can be determined as the VF detection interval threshold plus an offset, such as 60 ms. In yet other examples, cardiac electrical signal segments classified as VT / VF based on GMA may meet the criteria for discontinuing treatment. It should be recognized that multiple criteria for discontinuing treatment can be defined and applied by control circuitry 80 to the RRI until ATP or CV / DF shock delivery is used to determine if the rhythm is slowed, thereby justifying the discontinuation of ATP or CV / DF shock therapy.

[0108] When the treatment abortion criteria are met during charging state 3 in box 106, control circuit 80 may terminate the charging of the high-voltage capacitor by treatment delivery circuit 84 (if charging has not yet been completed), cancel the pending CV / DF shock, and proceed to re-detection state 5 in box 110. Operation during re-detection state 5 is further described below. If a segment of cardiac signal is buffered or processed for GMA after transitioning to charging state 3 in box 106, GMA may continue without interruption. GMA results can be used to determine if treatment abortion is terminated, and / or if treatment abortion is met by control circuit 80 during re-detection state 5, for example, in conjunction with the following... Figure 13 Further description.

[0109] In some examples, the treatment delivery circuit 84 may be configured to deliver one or more ATP treatment sequences during capacitor charging in charging state 3 (box 106). Control circuit 80 may determine that treatment termination criteria are met during capacitor charging after ATP has been delivered and proceed to re-detection state 5 in box 110. In other examples, control circuit 80 may determine that termination criteria are met, which could be after ATP delivery, during capacitor charging, or after capacitor charging is complete. Although Figure 5Not shown, but in some examples, control circuitry 80 may transition back to the unrelated sensing state 1 of block 102 in response to the fulfillment of termination criteria during charging state 3. Detected VT / VF may terminate spontaneously, or a delivered ATP therapy may terminate a VT / VF episode without the need for a CV / DF shock.

[0110] When capacitor charging is completed before treatment discontinuation criteria are met for treatment delivery during charging state 3 (box 106), control circuitry 80 may transition to treatment delivery state 4 of box 108. Treatment delivery circuitry 84 may deliver ATP or CV / DF shocks after transitioning to state 4. Treatment delivery circuitry 84 may be controlled by control circuitry 80 to synchronize ATP or CV / DF shocks with the patient's intrinsic heart rhythm, for example, based on timing of a received Vsense signal. Treatment may be synchronized with a Vsense signal received outside the refractory period. Treatment may be delivered after a specified time interval following completion of charging. In other examples, CV / DF shocks may be delivered during state 4 without necessarily synchronizing with the patient's intrinsic heart rhythm. In some cases, treatment discontinuation criteria may be met after capacitor charging is completed but before treatment delivery, for example, while waiting for a synchronization event during treatment delivery state 4.

[0111] When a specified number of Vsense signals are refractory events (e.g., when three or another specified number of consecutive Vsense signals are received during the post-sensing ventricular refractory period), control circuit 80 may determine that the treatment discontinuation criteria are met after capacitor charging is complete. Control circuit 80 may also determine that the treatment discontinuation criteria are met after capacitor charging when a single RRI is greater than a slow interval threshold, or when any of the other examples of the treatment discontinuation criteria described above are met. It should be understood that at any time after capacitor charging has been initiated, if the treatment discontinuation criteria are met before treatment delivery, control circuit 80 may transition to the re-detection state 5 of block 110 without delivering treatment.

[0112] Following treatment delivery (which may be an ATP or CV / DF shock) in state 4 of box 108 (or when the criteria for discontinuing treatment are met prior to treatment delivery), control circuitry 80 may transition to redetection state 5 at box 110. VT / VF may be redetected by control circuitry 80 when a reduced NID (which may be referred to as “redetection NID” or “RNID”) is met after treatment delivery or after treatment has been discontinued due to meeting the criteria for discontinuing treatment. Control circuitry 80 may determine the satisfaction of RNID based on the Vsense signal received from sensing channel 83 or 85, which is selected as a reliable sensing channel for tachyarrhythmia detection when control circuitry 80 transitions to relevant state 2. In some examples, control circuitry 80 may redetect VT / VF when RNID is met and no VT / VF rejection rule applied during redetection state 5 is met. RNID may be, for example, 25%, 30%, 50%, 60%, or 70% of the NID required for transitioning from irrelevant state 1 to relevant state 2. When the probability of VT / VF is relatively high due to the previously known VT / VF detection performed in relevant state 2, RNID can be used by control circuit 80 for re-detection of VT / VF. If the VT / VF re-detection criterion is met in state 5, control circuit 80 can return to charging state 3 of block 106. The following example combines... Figure 13 The flowchart describes the method that can be performed by the control circuit 80 during the re-detection operation state 5 in block 110.

[0113] CV / DF shocks (once or multiple times) can be delivered by the treatment delivery circuit 84 to terminate VT / VF. Control circuit 80 can be configured to apply re-detection criteria and / or termination criteria to the cardiac electrical signal sensed by sensing circuit 86 (during re-detection state 5) after each CV / DF shock to determine whether the detected VT / VF has been terminated or whether additional shock is needed based on the satisfaction of the re-detection criteria. If the termination criteria are satisfied during re-detection state 5 before the re-detection criteria are satisfied, control circuit 80 can transition back to the indifferent sensing state 1 of block 102. The VTI / VFI counter can be reset to zero, and GMA can be disabled after transitioning to indifferent sensing state 1.

[0114] When control circuit 80 transitions back to the unrelated sensing state 1 of block 102, for example, when termination criteria are met, from the relevant state 2 of block 104 or from the re-detection state 5 of block 110, control circuit 80 may restore the sensitivity of sensing channels 83 and 85 to the programmed sensitivity (if the sensitivity was previously increased by setting a lower voltage amplitude as the R-wave sensing limit in response to the cardiac signal segment being classified as VT / VF based on GMA). When the sensitivity has been increased in the unrelated state 1 of block 102 and the criteria for transitioning to the relevant state 2 of block 104 (where the increased sensitivity is valid) are subsequently met, the increased sensitivity may remain valid during all subsequent rapid arrhythmia operating states reached in blocks 104, 106, 108, and 110 (during treatment delivery in state 4 of block 108, sensing circuit 86 may be blanked or disabled). The increased sensitivity of sensing circuit 86 can be used to sense ventricular event signals to determine, for example, when termination criteria are met (before and / or after treatment delivery), when criteria for cessation of treatment are met, to synchronize VT / VF shocks, and when re-detection criteria are met after treatment delivery. Whenever ICD 14 enters the irrelevant sensing state 1 of box 102, the sensitivity of sensing channels 83 and 85 can be restored to programmed sensitivity, for example, to user-programmed settings or default sensitivity settings.

[0115] Figure 6 yes Figure 5 The diagram 200 illustrates a conceptual state 1 unrelated to the tachyarrhythmic operating state. Sensing methods executed by the ICD 14 for detecting VT / VF, detecting termination of VT / VF, and re-detecting VT / VF are generally referred to as tachyarrhythmia sensing methods. Sensing methods executed by the ICD 14 for determining the need for bradycardia pacing (e.g., for detecting long pauses in ventricular activity) are generally referred to as bradycardia sensing methods. Both tachyarrhythmia sensing methods and bradycardia sensing methods may include interactions that can influence operations performed during the tachyarrhythmic operating state and during the bradycardia operating state.

[0116] refer to Figure 6 In block 120 of the irrelevant sensing state 1 of the rapid arrhythmia sensing method, each sensing channel 83 and 85 of the sensing circuit 86 can sense ventricular event signals, such as R waves, according to programmed sensitivity. The control circuit 80 can determine the RRI between consecutively received Vsense signals received from a given sensing channel for counting VTI and VFI in VTI and VFI counters (and in some examples, combined VT / VF interval counters) specified for each respective sensing channel.

[0117] Combined with the following text Figure 7Further described, when a sensing channel 83 or 85 reaches NID (based on the RRI determined according to the Vsense signal received from that sensing channel), the control circuit 80 can analyze the sensing event data determined for the Vsense signals received from both sensing channels 83 and 85 to select one of sensing channels 83 or 85 as the reliable sensing channel for VT / VF detection. If the selected sensing channel 83 or 85 is the sensing channel that has reached NID, the control circuit 80 can transition to the relevant state 2 of block 104 (as indicated by arrow 129). The selected sensing channel is used to sense ventricular event signals (and generate the corresponding Vsense signal) upon transition to the relevant state 2 of block 104. The control circuit 80 can use the Vsense signal received from the selected sensing channel for a rapid arrhythmia sensing method to detect VT / VF, including updating the VTI and VFI counters, terminating detection, detecting treatment abortion status, re-detecting VT / VF, and any other operations that require ventricular event signal sensing, such as determining RRI and triggering the storage of sensing event signal segments for R-wave morphology matching or other sensing event signal analysis, as further described below.

[0118] However, if the selected sensing channel is not a sensing channel that has reached NID, the control circuit 80 may remain in the irrelevant state 1 of block 102. The control circuit 80 may continue to use the Vsense signals received from both sensing channels 83 and 85 to count the VTI and VFI of each respective sensing channel. When the VTI or VFI counters of both sensing channels 83 and 85 reach NID, the control circuit 80 may transition to the relevant state 2 of block 104 (as indicated by arrow 129).

[0119] When operating in the irrelevant state 1 of block 102, sensing channels 83 and 85 can sense ventricular event signals based on programmed sensitivity. During ventricular event sensing with programmed sensitivity (block 120), control circuitry 80 can determine, based on ventricular event sensing, when the criteria for suspected VT / VF insufficiency (also referred to herein as "suspected tachyarrhythmia insufficiency") are met. The following is in conjunction with... Figure 8 A method for detecting suspected VT / VF sensing insufficiency is described. In one example, control circuitry 80 can detect suspected VT / VF sensing insufficiency when the RRI determined based on the Vsense signal received from sensing channels 83 or 85 is greater than a sensing insufficiency threshold. The following section combines... Figure 8 Other examples of standards described for detecting suspected VT / VF insufficiency.

[0120] When a suspected VT / VF insufficiency is detected (as indicated by arrow 123), control circuitry 80 may trigger a morphological signal analysis (GMA) of the cardiac signal segment at block 124. In some examples, when control circuitry 80 does not require further morphological signal analysis for tachyarrhythmia or bradycardia sensing methods, morphological sensing channel 87 may be de-energized or disabled until the GMA is triggered by control circuitry 80, for example, to conserve power 98. In other examples, cardiac signal segments may be buffered from morphological signal channel 87 in memory 82 but not processed and analyzed by control circuitry 80 according to the GMA until the GMA is triggered, for example, based on the detection of a suspected VT / VF insufficiency. If the GMA is not triggered, the buffered cardiac signal segments may be discarded or overwritten by new cardiac signal segments, for example, according to a first-in, first-out (FIFO) principle.

[0121] When the GMA is triggered, the control circuit 80 buffers an n-second cardiac signal segment in memory 82 for processing and analysis to determine the presence of morphological evidence of VT / VF in the cardiac signal segment. Based on the GMA (box 124), the control circuit 80 can classify the cardiac signal segment into a VT / VF segment, a non-VT / VF segment, or a cardiac arrest segment. The following section combines... Figure 9 An example of a GMA method, which can be executed by control circuitry 80 to classify cardiac signal fragments as VT / VF, non-VT / VF, or cardiac arrest, is described.

[0122] When a cardiac signal segment is not classified as VT / VF (e.g., classified as cardiac arrest or non-VT / VF), control circuitry 80 may return to block 120 (as indicated by arrow 125). Sensing channels 83 and 85 may continue to sense ventricular event signals according to programmed sensitivity and update the VTI and VFI counters when an RRI is determined between Vsense signals and the RRI falls within the corresponding VT detection interval or VF detection interval.

[0123] Referring again to box 124, when the cardiac signal segment is classified into VT / VF based on the GMA performed at box 124, sensing circuit 86 may proceed to box 122 (as indicated by arrow 127) and may increase the sensitivity of sensing channel 83 and / or sensing channel 85 for sensing ventricular event signals. In some examples, the sensitivity of both sensing channels 83 and 85 is increased by decreasing the voltage amplitude of the sensitivity setting, for example, by lowering the sensing threshold. The sensitivity of both sensing channels 83 and 85 may be increased to a maximum sensitivity, for example, to the minimum available voltage amplitude setting that defines the sensing threshold. For convenience, the exemplary examples described herein refer to adjusting both sensing channels 83 and 85 according to the maximum sensitivity to control the R-wave sensing threshold in response to the VT / VF classification of the cardiac signal segment caused by the GMA. It should be noted that "maximum sensitivity" refers to the lowest voltage amplitude setting that can be used by sensing circuit 86, which in various examples may be in the range of tens of microvolts to millivolts (mV). For example, as an example, the sensitivity can be programmable in the range of 0.03mV to 2.0mV or between 0.075mV and 1.2mV. Therefore, in various examples, the maximum sensitivity can be a voltage amplitude of 0.03mV, 0.05mV, 0.075mV, 0.1mV, or 0.15mV, and can be any minimum voltage amplitude setting that can be used by the sensing circuit 86 as a sensing limit for sensing ventricular event signals.

[0124] However, it should be understood that in other examples, in response to a cardiac signal segment being classified as a VT / VF segment, sensing circuitry 86 may increase the sensitivity of sensing channel 83 or sensing channel 85 at block 122, but not necessarily the sensitivity of both. In yet another example, sensing circuitry 86 may increase the sensitivity of one or both of sensing channels 83 and / or 85 toward a maximum sensitivity (e.g., toward the minimum available voltage amplitude setting for the sensitivity), but not necessarily to the maximum sensitivity. For example, sensing circuitry 86 may adjust the sensitivity to half or another fraction or percentage of the current voltage amplitude setting of the programmed sensitivity, or may reduce the voltage amplitude setting by a specified amount or to the next lower voltage amplitude setting available in various examples.

[0125] If, after increasing sensitivity, a NID is achieved based on the ventricular event signal received from at least one sensing channel 83 or 85, and that channel is selected as a reliable sensing channel for VT / VF detection (as described below) Figure 7If the control circuit 80 transitions to the relevant state 2 of box 104 (as indicated by arrow 129), then the control circuit 80 may transition to the relevant state 2 of box 104. By increasing the sensitivity, a lower sensing threshold can now be used to sense R waves or fibrillation waves that may have been under-sensitized during VT / VF episodes (as confirmed by GMA results), thereby enabling the VTI and VFI counters to correctly track the VTI and VFI and reach the corresponding NID. Therefore, the effective sensitivity when the VTI or VFI counter of one or both sensing channels meets the NID can be either programmed sensitivity or increased sensitivity. After transitioning to the relevant state 2 of box 104, the effective sensitivity upon reaching the NID remains effective for sensing ventricular event signals through the selected sensing channel 83 or 85. The effective sensitivity upon transitioning to state 2 remains effective until the control circuit 80 transitions from any of the tachyarrhythmia operating states 2, 3, or 5 back to the irrelevant state 1 of box 102 (as described above). Figure 5 (The method described).

[0126] Referring again to boxes 124 and 122, if a GMA at box 124 results in a VT / VF classification of a cardiac signal segment (e.g., as indicated by arrow 127), control circuitry 80 may continue performing GMA on at least one or more subsequent cardiac signal segments at box 122. One or more cardiac signal segments received sequentially from morphological sensing channel 87 may be buffered in memory 82 for processing and analysis by control circuitry 80 at box 122, in irrelevant sensing state 1. GMA may continue to be performed by control circuitry 80 at box 122 until at least one cardiac signal segment (or another specified number of cardiac signal segments) is not classified as VT / VF (e.g., classified as cardiac arrest or non-VT / VF). If a cardiac signal segment is classified as cardiac arrest or non-VT / VF, for example, as indicated by arrow 128, control circuitry 80 may return to box 120 and restore the programmed sensitivity of sensing channel 86.

[0127] In some examples, GMA is performed a maximum number of times, for instance, by analyzing the maximum number of cardiac signal segments. In one example, GMA can be performed on up to three cardiac signal segments at box 122 (this corresponds to approximately 9 to 12 seconds of operation with increased sensitivity in box 122). If a cardiac signal segment is not classified as VT / VF, control circuitry 80 returns to box 120. If three consecutive cardiac signal segments are classified as VT / VF, control circuitry 80 can determine, based on the state of the VTI / VFI counter, whether to transition to box 120 and restore the programmed sensitivity settings or transition to state 2.

[0128] In some examples, when a threshold number of cardiac signal segments are classified as VT / VF based on GMA, control circuitry 80 may transition to relevant state 2 of block 104 (as indicated by arrow 130) before sensing channels 83 or 85 reach a NID. For example, when consecutive cardiac signal segments of a threshold number are classified as VT / VF based on GMA and at least one of the VTI counters or VFI counters of sensing channels 83 or 85 has reached at least a specified percentage of the corresponding NID, control circuitry 80 may transition to relevant state 2 of block 104 (arrow 130). In an exemplary example, if the NID used for VF detection is 30 VFIs out of 40 RRIs, and at least 20 VFIs have been counted for one sensing channel 83 or 85, then control circuitry 80 may transition to relevant state 2 of block 104 when at least three consecutive cardiac signal segments are classified as VT / VF. Sensing channels 83 or 85, which have a number of VTI / VFI counters that meet the threshold of VTI or VFI, can be selected as reliable sensing channels for detecting VT / VF after transitioning to correlated state 2.

[0129] Other criteria are conceivable for forcibly transitioning to relevant state 2 when sufficient evidence of a suspected VT / VF attack is detected, prior to meeting NID but with the presence of one or more cardiac signal segments classified as VT / VF according to GMA and an increasing trend in the VTI and / or VFI counters of at least one sensing channel 83 or 85. For example, if three cardiac signal segments are classified as VT / VF and most recent RRIs are counted as VTI or VFI, control circuit 80 may transition to state 2 of block 104. In various examples, if at least two, three, or other threshold number of consecutive cardiac signal segments are classified as VT / VF based on GMA, and the VTI / VFI counters have reached at least a threshold percentage of NID and / or for at least one sensing channel 83 or 85, a specified number of recent RRIs (e.g., the most recent 8, 10, or 12 RRIs) at least a threshold percentage (e.g., 60%, 75%, 80%, or 100%) are VTI and / or VFI, then control circuit 80 may force a transition to the relevant state 2 of block 104 before satisfying NID.

[0130] After control circuit 80 transitions to the relevant state 2 of block 104, GMA can remain enabled until control circuit 80 transitions back to the unrelated sensing state of block 102. Control circuit 80 can continue to buffer cardiac signal segments in memory 82, and in conjunction with the above... Figure 5 GMA is performed on cardiac signal segments under any of the described rapid arrhythmia operating states 2, 3, or 5.

[0131] Referring again to block 122, if the NID is not satisfied and a threshold number of cardiac signal segments have been analyzed and classified as VT / VF, the control circuit 80 may return to block 120 (as indicated by arrow 128, where the standard N GMAs = VT / VF and VTI / VFI < M, and in various examples, M may be equal to the NID or a specified percentage of the NID). If the VTI / VFI counter does not tend to increase when a threshold number of cardiac signal segments are classified as VT / VF (as indicated by arrow 130), for example, has not reached a specified percentage of the NID, the control circuit 80 may return to block 120 (as indicated by arrow 128). For example, if all VTI / VFI counters are zero, less than five, less than ten, or less than twenty (or other specified thresholds less than or equal to the NID in various examples) and the maximum number of consecutive cardiac signal segments have been analyzed (and classified as VT / VF), the control circuit 80 may return to block 120. It may be assumed that if a true VT / VF episode occurs, after increasing the sensitivity of sensing channels 83 and 85 for sensing ventricular event signals, at least one of sensing channels 83 or 85 will reach the NID within a threshold number of cardiac signal segments.

[0132] Upon transitioning back to block 120, the control circuit 80 may restore the sensitivity of sensing channels 83 and 85 to their programmed values. The control circuit 80 may interrupt the buffering of cardiac signal segments and / or the execution of the GMA (if the GMA is not currently triggered by the bradycardia sensing method as described below). The GMA may be interrupted to conserve power 98 and reduce the processing burden.

[0133] In some examples, when a suspected long pause (in ventricular activity) is detected, the control circuit 80 may trigger the GMA of cardiac signal segments during the bradycardia sensing method. As used herein, "long pause" refers to the minimum specified time interval during which ventricular activity is not detected according to the bradycardia sensing method disclosed herein. For example, a long pause may occur when ventricular activity has not been sensed for at least 3 seconds to 9 seconds. Ventricular activity may be detected based on the Vsense signal received from one or both of sensing channels 83 and / or 85 and / or based on the GMA of cardiac signal segments. In some examples, the GMA triggered by the bradycardia sensing method for detecting or confirming a long pause may affect the tachyarrhythmia sensing method. As shown by arrow 126 in block 102, for example, when the GMA triggered by the bradycardia sensing method results in a VT / VF classification of the analyzed cardiac signal segments, the control circuit 80 may advance from block 120 to block 122.

[0134] For example, when control circuit 80 operates in block 120 of an irrelevant tachyarrhythmia operating state, it performs ventricular event signal sensing using programmed sensitivity, and control circuit 80 can receive Vsense signals from both sensing channels 83 and 85 for use in bradycardia sensing and tachyarrhythmia sensing methods. Control circuit 80 can perform a first analysis on the Vsense signal received from sensing circuit 86 to detect a suspected long pause during the pause detection interval. Control circuit 80 can perform a second analysis on the Vsense signal received from sensing circuit 86 to detect a suspected VT / VF insufficiency at block 120 of the relevant state 1 of the tachyarrhythmia operating state. If the first analysis results in a suspected long pause detection or if the second analysis results in a determination of a suspected VT / VF insufficiency, control circuit 80 can trigger GMA execution to confirm the possibility of a long pause or confirm the possibility of VT / VF insufficiency, respectively.

[0135] The first analysis for detecting a suspected long pause may include determining whether any Vsense signal is received during the long pause detection interval (which, for example, may be 2 to 3 seconds long). Generally, if a Vsense signal is received, control circuitry 80 may evaluate the peak amplitude of the cardiac electrical signal sensed by one or both of sensing channels 83 and 85, for example, during the post-sensing blanking period, to determine whether the Vsense signal is reliable. When no reliable Vsense signal is received during the long pause detection interval, control circuitry 80 may detect a suspected long pause. Thus, as indicated by arrow 126 in block 102, when a cardiac signal segment is classified as VT / VF based on the GMA triggered by the bradycardia sensing method, sensing circuitry 86 may operate according to the programmed sensitivity in block 120 during irrelevant state 1. Control circuitry 80 may proceed to block 122. Example methods that can be executed by control circuitry 80 to trigger GMA according to bradycardia sensing methods and tachyarrhythmia sensing methods are generally described in U.S. Provisional Patent Application No. 63 / 486,725 (Greenhut et al., filed February 24, 2023), which is incorporated herein by reference in its entirety.

[0136] According to any of the examples described above, sensing circuit 86 may increase the sensitivity of sensing channels 83 and 85 at block 122. Control circuit 80 may perform at least one additional GMA for subsequent cardiac electrical signal segments at block 122. In some examples, control circuit 80 may additionally require all VTI / VFI counters for both sensing channels to be below a threshold value in order to advance from block 120 to block 122 in response to the cardiac signal segment being classified as a VT / VF segment when the bradycardia sensing method triggers the GMA. For example, control circuit 80 may require all VTI / VFI counters to be 0 or less than 3, 5, 8, 10, 12, 15, 20, or other thresholds in order to advance to block 122 and increase the sensitivity of sensing circuit 86. When the VTI / VFI counters are greater than the threshold, it indicates that the Vsense signal is received and counted at VTI and / or VFI, and VT / VF undersensitization may not occur. The increased sensitivity may be unnecessary. However, when all VTI / VFI counters are below the threshold and VT / VF classification is performed on cardiac signal segments, control circuit 80 can increase sensitivity by advancing to block 122 to avoid undersensitivity of low-amplitude R waves and fibrillation waves that may occur at uncounted VT / VF intervals.

[0137] Control circuit 80 may continue to perform GMA on cardiac signal segments received from morphological signal channel 87 at block 122 until any of the conditions for transitioning to relevant state 2 are met, or until at least one cardiac signal segment is not classified as VT / VF (arrow 128), or until a threshold number of VT / VF classifications are performed based on GMA, but according to any of the examples described above, the NID does not tend upward despite the increased sensitivity of sensing channel 86. While control circuit 80 operates in block 122 (where sensing circuit 86 operates according to increased sensitivity), the Vsense signal received from sensing channels 83 and 85 in response to sensing ventricular event signals according to increased sensitivity can be used by control circuit 80 for both the tachyarrhythmia sensing method and the bradycardia sensing method. In this way, control circuit 80 may increase the sensitivity of sensing channels 83 and / or 85 for tachyarrhythmia sensing based on the bradycardia sensing method performed to detect long pauses and the need for bradycardia pacing. Conversely, control circuitry 80 may increase the sensitivity of sensing channels 83 and / or 85 for bradycardia sensing based on rapid arrhythmia sensing methods performed to detect suspected VT / VF insufficiency and the need for CV / DF shock.

[0138] Figure 7This is a flowchart 250 illustrating a method, according to some examples, that can be executed by control circuitry 80 for selecting a reliable sensing channel for detecting VT / VF. Control circuitry 80 can respond to satisfying the transition... Figure 5 The relevant state 2 conditions of box 104 are used to select a reliable sensing channel.

[0139] At box 251, control circuit 80 operates in unrelated sensing state 1. Figure 6 (Block 102). Control circuit 80 receives Vsense signals from both sensing circuit 86 and sensing channel 83 and sensing channel 85 when Vsense signals are generated. In response to each Vsense signal, sensing circuit 86 and control circuit 80 can collaboratively determine sensing event data at block 252. The sensing event data can be buffered in memory 82 for analysis to select a reliable sensing channel for detecting VT / VF, for example, when an NID is reached based on the Vsense signal received from one of sensing channels 83 or 85.

[0140] Sensing circuit 86 and control circuit 80 can collaboratively determine sensing event data at block 252 by determining a matching or mismatched sensing event classification, a noise metric, the peak amplitude of the sensing event, the amplitude of the R-wave sensing threshold that causes the generation of the Vsense signal to be exceeded, and the RRI. Control circuit 80 can define the RRI as the time interval from the currently received Vsense signal to the most recent Vsense signal received from the same sensing channel 83 or 85 (or, in some cases, from a previous pacing pulse) within the same channel. The RRI, also referred to herein as the "ventricular sensing event interval," can be buffered in memory 82.

[0141] In response to the Vsense signal, the sensing circuit 86 can initiate an intra-channel blanking period applied by the corresponding sensing channel 83 or 85 to the received cardiac electrical signal, for example, to avoid sensing the same signal twice. During the intra-channel blanking period, the R-wave detector 66a or 66b of the corresponding sensing channel 83 or 85 can be activated, for example. Figure 4 The peak tracking and holding circuit (shown) determines the maximum peak amplitude of the sensed signal. The maximum peak amplitude can be buffered in memory 82 in conjunction with the RRI at block 152 as sense event data corresponding to the Vsense signal.

[0142] Control circuit 80 can determine the amplitude to sensing threshold ratio (ASTR) at block 252 as sensing event data for each Vsense signal. ASTR can be determined by determining the ratio of the maximum peak amplitude determined during the blanking period within the channel to the amplitude of the R-wave sensing threshold when the cardiac electrical signal exceeds the R-wave sensing threshold to generate a Vsense signal.

[0143] A noise metric can be determined at block 252 by sensing circuitry 86 and / or control circuitry 80 to evaluate the noise level of the cardiac electrical signal at the Vsense signal. In some examples, the noise metric can be determined as a noise pulse count by counting the number of signal pulses that exceed a noise pulse threshold amplitude during the in-channel blanking period. The noise pulse threshold amplitude can be equal to or based on the R-wave sensing threshold amplitude that the cardiac electrical signal exceeds to generate the Vsense signal. The noise pulses can be counted by applying the noise pulse threshold to a narrowband, notch-filtered, and rectified signal received by the respective R-wave detector 66a or 66b during the in-channel blanking period. The noise pulse count representing the number of signal pulses with an amplitude greater than or equal to the R-wave sensing threshold amplitude at the Vsense signal during the in-channel blanking period can represent the noise level of the cardiac electrical signal at the Vsense signal. In other examples, the noise metric can be determined by counting the number of signal peaks, zero-crossings, determining the average amplitude, average slope, or other characteristics of the cardiac electrical signal during the in-channel blanking period. Noise metrics can be buffered in memory 82 in association with the RRI and other sensed event data determined for the Vsense signal at box 252. In other examples, noise metrics can be compared to a threshold or range to identify sensed event signals as noisy events. Vsense signals can be classified as noisy or noiseless events based on noise metrics. Noisy or noiseless event classifications can be buffered in memory 82 at box 252 along with other sensed event data corresponding to the Vsense signal. For example, if the noise pulse count is at least 3, 4, 5, 6, or other specified threshold number, the noisy event classification can be stored along with the sensed event data for the corresponding Vsense signal.

[0144] Control circuitry 80 can determine at block 252 whether the current Vsense signal is a matched event signal or a mismatched event signal. The current Vsense signal is a matched signal when control circuitry 80 receives a Vsense signal from another sensing channel 83 or 85 within a specified time window of the current Vsense signal. For example, control circuitry 80 can classify and buffer matched event signals for the current Vsense signal in memory 82 before or after a Vsense signal received from another sensing channel within the matched window. In one example, the matched window can be a 160ms time window, which can extend 80ms earlier and 80ms later than the current Vsense signal. If no other Vsense signal is received from another sensing channel during the matched window, control circuitry 80 can classify and buffer mismatched event signals for the current Vsense signal in memory 82 at block 252. In various examples, the matched window can be 50ms to 200ms long and can extend (equally or unequally) before and / or after the time of the current Vsense signal.

[0145] For each Vsense signal received from each sensing channel 83 and 85, control circuitry 80 may determine and buffer RRI, peak amplitude, ASTR, noise metric (or noisy event or noisy event classification), and matched or mismatched event classification. This sensing event data determined for the Vsense signal may be stored in a buffer in memory 82, which is allocated for storing sensing event data for the corresponding sensing channel. In other examples, other characteristics of the cardiac electrical signal received from the corresponding sensing channel 83 or 85 may be determined and buffered as sensing event data in memory 82 for use in determining a reliable sensing channel for VT / VF detection. For example, in addition to or alternative to these data, such as RRI, peak amplitude, ASTR, noise metric, and match / mismatch classification, other cardiac signal characteristics that can be determined from the cardiac electrical signals received from sensing channels 83 or 85 may include: positive peak slope; negative peak slope; R-wave template morphology match score; signal width of the maximum amplitude pulse after the R-wave sensing threshold is exceeded; maximum signal width; number of signal pulses with a signal width less than the threshold signal width; sum of pulse widths during the blanking interval (or another baseline portion of the cardiac electrical signal); or any combination of any of these examples.

[0146] The sensing event data determined by the control circuit 80 and stored in the memory 82 may include data used by the control circuit 80 to determine whether a rejection rule for suppressing VT / VF detection is satisfied when NID is reached. (The following is in conjunction with...) Figure 11 and Figure 12Examples of sense event data that can be determined for applying a rejection rule when NID is satisfied are described. The sense event data determined in response to the Vsense signal may depend on the value of the VTI / VFI counter. For example, when the VTI / VFI counter has reached at least a threshold (e.g., 3, 5, 8, or other specified value), the morphological sensing channel 87 may be enabled to transmit a morphological signal, based on which the R-wave morphological matching score can be determined as sense event data.

[0147] It should be understood that the control circuit 80 may buffer two different types of cardiac signal segments in the memory 82 for processing and analysis. The control circuit 80 may buffer sense event signal segments for analysis of sense event signals to determine sense event data. These sense event signal segments are different from the cardiac signal segments acquired and buffered for performing GMA. The sense event signal segments are buffered in response to a Vsense signal received from the sensing circuit 86. Compared to the cardiac signal segments acquired for performing GMA, the sense event signal segments can be relatively short. For example, by way of example, the sense event signal segments may be 500 ms or less, or 350 ms or less. The sense event signal segments are intended to cover the signal waveform sensed by one of the sensing channels 83 and / or 85, causing the sensing circuit 86 to generate a Vsense signal. Therefore, the signal waveform buffered in the sense event signal segments corresponds to a sense event signal and a corresponding Vsense signal generated by the sensing channel (although both sensing channels 83 and 85 may generate a Vsense signal in response to sensing the same signal waveform). The sensed signal waveform buffered in the sensed event signal segment can be a real R wave or fibrillation wave, but it can also be an oversensitized signal, such as an oversensitized P wave, T wave, or non-cardiac noise signal. Therefore, the sensed event signal segment buffered for R-wave morphology matching (and / or other sensed event signal analysis) is used to select a reliable sensed channel for VT / VF detection and / or to determine whether rejection rules for suppressing VT / VF detection are met (e.g., as described below). Figure 11 and Figure 12 The described event signal segment depends on the Vsense signal received from sensing channel 83 or 85. That is, a sensing event signal segment of the shape signal received from shape sensing channel 87 can be captured by control circuitry 80 in response to the receipt of the Vsense signal. The sensing event signal segment has a start and end time defined relative to the timing of the Vsense signal.

[0148] In contrast, the cardiac signal segment acquired for GMA can be relatively longer than the sensing event signal segment and can begin and end independently of the timing of any Vsense signal. In the exemplary examples presented herein, the cardiac signal segment for the GMA buffer can be, for example, 1 second to 6 seconds or 3 seconds long. The cardiac signal segment used for GMA can have a duration greater than the total duration of multiple VT or VF detection intervals, for example, five to ten times longer than the VT or VF detection interval. The sensing event signal segment has a total duration covering the Vsense signal within a single channel, while the cardiac signal segment for the GMA buffer may have one or more Vsense signals occurring during the cardiac signal segment, but the timing of the start and end of the cardiac signal segment can be independent or random relative to any Vsense signal that occurs. (See below for further details.) Figure 14 As described, during pacing following bradycardia or shock, relatively short cardiac signal segments (e.g., 0.3 to 1.0 seconds segments) can be buffered for GMA between pacing pulses, allowing GMA results to be determined from multiple cardiac signal segments covering a total time greater than multiple VT or VF detection intervals. The cardiac signal segments acquired for GMA may include or may not include the timing of any Vsense signal, and are independent of the timing of any Vsense signal. The time interval of the cardiac signal segments used for GMA may be independent of receiving Vsense signals, because in some cases, Vsense signals are not received when the cardiac signal segments are buffered. Depending on how many Vsense signals (if any) are received from sensing circuitry 86 during the cardiac signal segment, any sensing event signal segments may not be buffered, or one or more sensing event signal segments may be buffered.

[0149] At block 254, control circuit 80 determines whether the VTI / VFI counter used for sensing channel 83 or 85 has reached NID based on the RRI determined for the Vsense signal received from the respective sensing channel 83 or 85. If the VTI / VFI counter used for both sensing channels 83 and 85 is less than the corresponding NID used for detecting VT or VF, control circuit 80 can remain in the uninvolved sensing state 1 by returning to block 251. However, as Figure 7 As shown and in conjunction with the above Figure 6 As described, if a threshold number (e.g., 3) of cardiac signal segments are classified as VT / VF based on GMA (decision box 255) and the VTI / VFI counter tends upward (e.g., has reached at least a specified percentage of NID), then control circuitry 80 may select the sensing channel for VT / VF detection at box 258. Control circuitry 80 may transition to relevant state 2 at box 266.

[0150] At block 258, control circuitry 80 may select sensing channel 83 or 85 in response to N GMA results being VT / VF and at least one VTI / VFI counter reaching a threshold percentage of NID. The selected sensing channel may be associated with a VTI / VFI counter that has reached the threshold percentage of NID. If both sensing channels 83 and 85 have reached the threshold percentage of NID, the selected sensing channel may be a programmed default sensing channel or sensing channel 83 or 85 that has recently been selected as a reliable sensing channel for VT / VF detection. In other examples, sensing channel 83 or 85 associated with the highest VTI, VFI, or combined VTI and VFI counts may be selected as a reliable sensing channel at block 258. The Vsense signal received from the selected sensing channel 83 or 85 may be used by control circuitry 80 to adjust the VTI / VFI counters for VT / VF detection and to detect long pauses to initiate ventricular pacing according to a bradycardia sensing method, while control circuitry 80 operates in relevant state 2 to detect VT / VF.

[0151] Referring again to block 254, when control circuitry 80 determines that NID has been reached (“Yes” branch), control circuitry 80 determines at block 256 whether only one sensing channel 83 or 85 reaches NID or whether the VTI / VFI counters of both sensing channels 83 and 85 reach NID. In some cases, the VTI / VFI counters of both sensing channels 83 and 85 may reach the NID required for VT / VF detection at approximately the same time (e.g., on the same matched Vsense signal). When the VTI / VFI interval counters associated with both sensing channels 83 and 85 have reached NID (“Yes” branch of block 256), control circuitry 80 may select a default sensing channel at block 258 and transition to associated state 2 at block 266. The default sensing channel may be a programmed default sensing channel or sensing channel 83 or 85 that has recently been selected as a reliable sensing channel for VT / VF detection (according to the method described below in conjunction with blocks 260-262). The Vsense signal received from the selected sensing channel 83 or 85 is used to adjust the VTI / VFI counter for VT / VF detection and can be used in the bradycardia sensing method until the control circuit 80 transitions from either the tachyarrhythmia operating state 2 or 5 back to the indifferent sensing state 1 (see...). Figure 5 ).

[0152] Referring again to block 256, when only one sensing channel 83 or 85 reaches NID—for example, when the VTI / VFI counter associated with one sensing channel 83 or 85 has not yet reached NID, but the VTI / VFI counter associated with another sensing channel has reached NID—control circuitry 80 may proceed to block 260. At block 260, control circuitry 80 may determine a sensing event metric based on sensing event data buffered in memory 252 for selecting a reliable sensing channel. Control circuitry 80 may analyze the buffered sensing event data to determine which sensing channel 83 or 85 is considered most reliable for detecting VT / VF.

[0153] At block 260, control circuitry 80 can determine a sensing event metric for each sensing channel 83 and 85 based on sensing event data buffered at block 252. Sensing event data can be retrieved for a specified number of recent Vsense signals for each sensing channel 83 and 85. Sensing event data can be retrieved for all Vsense signals received from both sensing channels 83 and 85 during a specified time interval before a sensing channel 83 or 85 reaches NID. In some examples, the sensing event metric can be determined based on sensing event data buffered for Vsense event signals received within the most recent specified time interval (e.g., within the most recent 3 seconds) (up to a specified maximum number of recent Vsense events). For illustrative purposes, the sensing event metric can be determined for the most recent M Vsense signals from each sensing channel, where M can be the same or different for each sensing channel, and the M Vsense signals occurred within the most recent 3 seconds or less before one of the sensing channels 83 or 85 reached NID.

[0154] The sensing event metric for each sensing channel 83 and 85 is determined from the sensing event data storage of the respective sensing channels. The sensing event metric determined by the control circuitry 80 at block 260 may include the maximum RRI in the buffer RRI determined for each sensing channel 83 and 85. The sensing event metric determined by the control circuitry 80 at block 260 may include a representative peak amplitude, for example, an average peak amplitude determined based on the peak amplitude of the Vsense signal buffer for each sensing channel 83 and 85.

[0155] The sensing event metric determined by the control circuitry 80 at block 260 for each sensing channel 83 and 85 may include the match event ratio. The match event ratio may be determined as the ratio of the number of Vsense signals classified as match events to the total number M of Vsense signals evaluated for the corresponding sensing channel 83 or 85.

[0156] The sensing event metric determined by the control circuitry 80 at block 260 for each sensing channel 83 and 85 may include the Match-Mismatch Event Amplitude Ratio (MUAR). MUAR may be determined as the median (or other representative value) of the peak amplitudes of the Vsense signals classified as match event signals and the median (or other representative value) of the peak amplitudes of all Vsense signals classified as mismatch event signals. In some examples, MUAR may be set to 0 if all M Vsense signals for a given sensing channel 83 or 85 are classified as match events.

[0157] The sensing event metric determined by control circuitry 80 for each sensing channel 83 and 85 may include a representative ASTR, such as an average ASTR, which is determined based on the ASTR of the Vsense signal buffer for each respective sensing channel. The sensing event metric determined by control circuitry 80 for each sensing channel 83 and 85 may include a noisy pulse count. The noisy pulse count may be the number of Vsense signals classified as noisy events based on a noise metric (e.g., the number of signal pulses during the blanking period within the channel), which is greater than a noise threshold, such as 3, 5, 7, or other selected noisy event threshold.

[0158] At block 262, control circuitry 80 identifies sensing channel 83 or 85 associated with the achieved NID as a “candidate” sensing channel. For convenience, another sensing channel 85 or 83 associated with a VTI / VFI counter that has not yet reached an NID may be referred to as a “non-candidate” sensing channel. Control circuitry 80 may determine at block 262 whether the sensing event metric determined at block 260 meets the candidate sensing channel reliability criteria. In some examples, multiple criteria may be combined and applied to the sensing event metric to determine which of the candidate or non-candidate sensing channels is considered most reliable for sensing ventricular event signals used for VT / VF detection.

[0159] In various examples, a combination of criteria for verifying reliable sensing by the candidate sensing channel during possible VT / VF periods can be applied by control circuitry 80 to a sensing event metric. Possible VT / VF criteria may include a criterion applied to the matched event ratio of the candidate sensing channel. Possible VT / VF criteria may include a criterion applied to the maximum RRI determined for non-candidate sensing channels. For example, control circuitry 80 may determine that possible VT / VF criteria are met when the matched event ratio of the candidate sensing channel is greater than or equal to a threshold ratio and the maximum RRI of the non-candidate sensing channel is less than a threshold interval. As an example, the matched event ratio of the candidate sensing channel may need to be at least 0.7, 0.8, or 0.9. For example, the maximum RRI of the non-candidate sensing channel may need to be less than the effective longest VT or VF detection interval plus an offset. As an example, the offset may be 30 ms, 40 ms, 50 ms, or 60 ms. The candidate sensing channel reliability criterion can be met at block 262 based on the matched event ratio of the candidate sensing channel and the maximum RRI of the non-candidate sensing channel satisfying the possible VT / VF criteria. When NID is reached for one sensing channel instead of two sensing channels due to some jitter in the timing of the Vsense signal received from a non-candidate sensing channel, the sensing event metric can meet the possible VT / VF criteria. Selecting a candidate sensing channel as the reliable sensing channel and transitioning to associated state 2 (box 266) avoids delays or missing VT / VF detections caused by jitter delays in the RRI determined from a sensing channel and the VTI / VFI counters associated with the non-candidate sensing channel reaching NID simultaneously with the candidate sensing channel.

[0160] Alternatively or additionally, control circuitry 80 may apply a second set of criteria to sensing event metrics to verify reliable sensing and the improbability of oversensing in candidate sensing channels. In one example, the set of criteria may include applying criteria to a noisy beat count determined for a candidate sensing channel. The set of criteria may include applying a threshold to a MUAR determined for a candidate sensing channel. The set of criteria may include applying a threshold to the average ASTR of the candidate sensing channels. In some examples, the set of criteria may include applying a threshold to the ratio of the average ASTR determined for candidate sensing channels to the average ASTR determined for non-candidate sensing channels. This ratio of average ASTR may be referred to as the candidate ASTR to non-candidate ASTR ratio. In one example, when the noisy beat count is zero and the MUAR of the candidate sensing channel is less than or equal to 1.3 and the candidate ASTR to non-candidate ASTR ratio is greater than or equal to 0.9, control circuitry 80 may determine at block 262 that the candidate sensing channel reliability criteria are met based on the improbability of reliable sensing and the improbability of oversensing in the candidate sensing channel. In various examples, the noisy beat count threshold can be 0, 1, or 2, and the MUAR threshold can be 1.2, 1.3, 1.4, or 1.5. In various examples, the threshold applied to the ratio of candidate ASTRs to non-candidate ASTRs can be 0.8, 0.9, or 1.0. These and other example values ​​of various thresholds, ranges, or other criteria applied to the sensing event metric are intended to be illustrative and non-limiting in nature. Selecting a candidate sensing channel and transitioning to relevant state 2 (box 266) when the sensing event metric indicates reliable sensing without oversensing of the candidate sensing channel enables the ICD 14 to detect VT / VF attacks with minimal delay before the non-candidate sensing channel has reached NID simultaneously with the candidate sensing channel.

[0161] Alternatively, control circuitry 80 may apply a third set of criteria to sensing event metrics to verify potential undersensitivity of non-candidate sensing channels at block 262, thereby indicating that candidate sensing channels are more reliable sensing channels for VT / VF detection. In one example, this set of criteria may include applying a threshold to the average peak amplitude determined for the non-candidate sensing channel. This set of criteria may also include applying a threshold interval to the maximum RRI determined for the non-candidate sensing channel. For example, a non-candidate sensing channel may be undersensitivity to low-amplitude R-waves or fibrillation waves when the average peak amplitude determined for M Vsense signals buffered for the non-candidate channel is less than a specified multiple of the sensing channel's sensitivity and the maximum RRI is greater than the threshold interval. Because non-candidate sensing channels may be undersensitivity, candidate sensing channel reliability criteria can be met at block 262. The specified multiple of sensitivity can be 1.5 times, 2.0 times, 2.5 times, 2.75 times, 3.0 times, 3.25 times, or 3.5 times the current effective sensitivity for the sensing channel. This effective sensitivity can be the programmed sensitivity or an increased sensitivity due to the classification of cardiac signal segments into VT / VF based on GMA (e.g., as combined above). Figure 6 (As described). The threshold interval can be 1250ms, 1500ms, 1750ms, 2000ms, or other specified threshold intervals. Insufficient sensing on non-candidate sensing channels may be possible when the average peak amplitude is relatively small (less than a multiple of the sensitivity) and at least one relatively long RRI has occurred in the last M Vsense events. Selecting a candidate sensing channel and transitioning to relevant state 2 (box 266) minimizes the likelihood of delayed detection of VT / VF attacks due to insufficient sensing on a sensing channel 83 or 85.

[0162] In response to meeting any of the applied candidate sensing channel reliability criteria at block 262, control circuitry 80 may transition to relevant state 2 at block 266. Candidate sensing channels may be selected sensing channels used by control circuitry 80 to determine RRI and other analyses performed for detecting VT / VF. Vsense event signals received only from candidate sensing channels may be used by control circuitry 80 to detect long pauses and reset the bradycardia pacing escape interval and / or to detect long pauses and control the delivery of bradycardia pacing pulses by treatment delivery circuitry 84 at other time intervals. In some examples, non-candidate sensing channels may be de-energized during relevant state 2 to conserve power 98.

[0163] When control circuit 80 determines that the reliability criteria for a candidate sensing channel are not met, control circuit 80 may remain in irrelevant sensing state 1 (at block 270). In this case, the non-candidate sensing channel may be considered a reliable sensing channel, such that the NID reached by the candidate sensing channel may be erroneously reached, for example, due to oversensing. Because the non-candidate sensing channel is the channel with a VTI / VFI counter that has not reached NID, control circuit 80 does not transition to relevant sensing state 2. The process of flowchart 250 may return to block 251. Control circuit 80 may continue to receive Vsense signals from both sensing channels 83 and 85, and determine sensing event data at block 252 until either or both of sensing channels 83 and / or 85 reach NID (or a threshold number of cardiac signal segments are classified as VT / VF and reach a specified percentage of NID).

[0164] While examples of three different combinations of criteria for determining when a candidate sensing channel reliability criterion is met are described herein, it should be understood that in various examples, fewer or more than three combinations of criteria may be applied to the sensing event metrics determined for one or two sensing channels. Furthermore, sensing event data and / or different sensing event metrics different from those described herein may be determined to determine when one sensing channel 83 or 85 is more reliable than another sensing channel 85 or 83, because when one sensing channel reaches NID while the other does not, a given sensing channel may be undersensing, oversensing, or reliably sensing without undersensing or oversensing. Methods performed by sensing circuitry 86 and control circuitry 80 for selecting reliable sensing channels for VT / VF detection and controlling when the transition from irrelevant state 1 to relevant state 2 occurs may include aspects of the technology generally disclosed in U.S. Patent Application No. 17 / 823,055 (Liu et al.), filed August 29, 2022, the contents of which are incorporated herein by reference in their entirety.

[0165] Figure 8 It can be controlled by circuit 80 in Figure 6 The flowchart 300 describes a method for detecting suspected VT / VF sensing insufficiency, executed during irrelevant sensing state 1. (As described above...) Figure 7 As described, control circuitry 80 can identify and store sensing event data for each Vsense signal received from each sensing channel 83 and 85 during irrelevant sensing state 1. For example, sensing event data for the most recent 8, 10, 16, 20, 30, or other specified number of Vsense signals for each sensing channel can be stored in a first-in-first-out buffer. Control circuitry 80 can analyze the sensing event data to determine when a suspected VT / VF sensing insufficiency criterion is met.

[0166] In various examples, control circuit 80 may analyze the RRI, peak amplitude, and / or morphology of the sensed event signal to determine whether VT / VF undersensing may occur. Generally, VT / VF undersensing occurs when sensing circuit 86 undersensits R-waves and / or fibrillation waves, causing VTI and / or VFI to be under-counted at a given point in time, which may delay or prevent the attainment of NID. The process in flowchart 300 includes examples of various criteria, such as thresholds or other values, that can be applied to sensed event data or measurements of sensed event data to determine if undersensing of R-waves and / or fibrillation waves may occur during a possible VT / VF episode.

[0167] At block 302, control circuitry 80 can determine the maximum RRI from the RRI buffered for both sensing channels 83 and 85. When the RRI determined for the Vsense signal received from either sensing channel 83 or 85 is greater than or equal to the undersense threshold interval as determined at block 304, control circuitry 80 can determine at block 306 that a suspected undersense criterion is met. The undersense threshold interval can be, for example, 1.5 seconds to 4 seconds, and in one example, 2.5 seconds.

[0168] As mentioned above Figure 6 As described, control circuitry 80 may initiate buffering and GMA of a cardiac signal segment in response to a suspected VT / VF insufficiency detection. In some examples, if buffering and GMA of a cardiac signal segment are already underway, for example due to a suspected long pause detection according to a bradycardia sensing method, the result of that GMA may be used by control circuitry 80 in response to a suspected VT / VF insufficiency detected at block 306, rather than buffering a new cardiac signal segment.

[0169] In some examples, if the maximum RRI is not at least the insufficient threshold interval (the "No" branch of box 304), amplitude and / or morphology criteria can be applied to the sensed event data when the VTI / VFI counter has started counting up but has not yet reached NID. At box 308, control circuitry 80 can determine whether the VTI / VFI count associated with either sense channel 83 or 85 is greater than a low threshold less than NID. The low threshold can be 2, 3, 4, 5, 8, 10, or other selected thresholds. The low threshold is referred to as "low" because when the threshold number of cardiac signal segments is classified as VT / VF based on GMA, this threshold can be a value or percentage of NID lower than the threshold VTI / VFI counter required to transition to tachyarrhythmic operating state 2 (e.g., as shown in the image). Figure 6 Arrow 130 is shown or combined with Figure 7(As described in block 255). If the VTI / VFI counts are both zero or less than a low threshold for both sensing channels 83 and 85 (the "No" branch of block 308), the control circuit 80 may determine at block 322 that the suspected VT / VF sensing insufficiency criterion is not met.

[0170] If the VTI / VFI counter associated with one sensing channel 83 or 85 is greater than a low threshold (the "Yes" branch of block 308), but not both sensing channels 83 and 85 (the "No" branch of block 310), and NID is not reached for either sensing channel, then control circuitry 80 may proceed to block 312 to determine and analyze the amplitude amount determined based on the buffered sensing event data stored for each sensing channel 83 and 85. For example, at block 312, control circuitry 80 may determine the amplitude amount based on the peak amplitude of the Vsense signal buffer for each sensing channel 83 and 85. (As described above...) Figure 7 As described, control circuitry 80 (or sensing circuitry 86) can determine the maximum rectified peak amplitude of each Vsense signal received from sensing channels 83 and 85 during the blanking period within the channel. At block 312, control circuitry 80 can determine the amplitude magnitude of each sensing channel 83 and 85 as a representative value of the peak amplitude buffered for each respective sensing channel 83 and 85, such as an average, median, minimum, maximum, or other representative value. In one example, the median peak amplitude of each sensing channel 83 and 85 is determined based on twelve (or other selected number) buffered peak amplitudes stored for the respective sensing channel 83 or 85.

[0171] At block 314, control circuitry 80 can compare the amplitude amount (e.g., representative peak amplitude) determined for each sensing channel 83 and 85 with a sensing insufficiency threshold amplitude. When the representative peak amplitude determined for sensing channel 83 and sensing channel 85 is less than the corresponding sensing insufficiency threshold amplitude, control circuitry 80 can proceed to block 316 to determine the R-wave morphology matching score for the next N Vsense signals. In other examples, control circuitry 80 can detect a suspected VT / VF sensing insufficiency at block 306 in response to the amplitude amount at block 314 being less than the corresponding sensing insufficiency threshold, without needing to determine and analyze the R-wave morphology matching score.

[0172] Control circuit 80 can apply the insufficient sensing threshold amplitude as a multiple of the programmed sensitivity for each corresponding sensing channel 83 and 85. When in Figure 6When executing the process of flowchart 300 at block 120, the programmed sensitivity of each sensing channel 83 and 85 can be valid. The undersensitivity threshold amplitudes applied to the representative peak amplitudes determined from each sensing channel 83 and 85 can be different from or the same as each other. For example, each undersensitivity threshold amplitude can be set based on the corresponding sensitivity of sensing channel 83 or 85 using the same or different multiples of the sensitivity. The multiples of the sensitivity used to set the undersensitivity threshold amplitude can range from 2 to 6, and as an example, can be between 2.5 and 5.

[0173] In an exemplary example, when the median peak amplitude determined based on the peak amplitude of the buffered sensing event of the first sensing channel 83 or 85 is less than 2.6 times the programmed sensitivity of the first sensing channel and the median peak amplitude determined based on the peak amplitude of the buffered sensing event of the second sensing channel 85 or 83 is less than 5 times the programmed sensitivity of the second sensing channel, the control circuit 80 may determine at block 314 that the amplitude is less than the corresponding undersensitivity threshold. The first sensing channel may be a sensing channel having a VTI / VFI count greater than the threshold (as determined at block 310), and the second sensing channel may be a sensing channel having a VTI / VFI count less than the threshold (as determined at block 310).

[0174] If the amplitude is not less than the corresponding insufficient sensing threshold (the "No" branch of block 314), the control circuit 80 can determine at block 322 that the suspected VT / VF insufficient sensing criterion is not met. No suspected VT / VF insufficient sensing is detected. The sensing circuit 86 can, for example, in Figure 6 Operation continues at box 120 according to the programmed sensitivity. Sensing circuit 86 may not perform sensitivity adjustment, and GMA may remain disabled (unless due to suspected long pause detection being enabled, in which case control circuit 80 proceeds to...). Figure 6 (Box 122).

[0175] In some examples, control circuitry 80 may detect suspected VT / VF insufficiency at block 306 when the amplitude at block 314 is less than the corresponding insufficiency threshold. However, in the example shown, control circuitry 80 may be configured to determine the R-wave morphology matching score and / or RRI of the next N Vsense signals to determine whether the suspected VT / VF insufficiency criterion is met. Therefore, control circuitry 80 may proceed to block 316 in response to the amplitude being less than the corresponding insufficiency threshold (the "Yes" branch of block 314).

[0176] Referring again to block 310, in some examples, if the VTI / VFI counters associated with both sensing channels 83 and 85 are greater than a low threshold—for example, if the VFI count for sensing channel 83 is at least 5 and the VFI count for sensing channel 85 is at least 5 (the "Yes" branch of block 310)—then control circuitry 80 may omit the amplitude analysis performed at blocks 312 and 314. Control circuitry 80 may proceed directly to block 316 to determine the R-wave morphology matching score for the next N Vsense signals.

[0177] In some examples, when the VTI / VFI counter reaches a low threshold (e.g., 2, 3, 4, or 5), control circuitry 80 may enable buffering of sensing event signal segments from the morphological signal received from morphological sensing channel 87. Morphological signal channel 87 may be powered down or disabled to conserve power 98 until control circuitry 80 requires the cardiac electrical signal (also referred to herein as the "morphological signal") sensed by morphological signal channel 87 for R-wave morphology matching, GMA, or other morphological correlation analysis. When the VTI / VFI counter reaches a low threshold or another specified value, sensing event morphological analysis of sensing event signal segments obtained in a time-correlated manner with the Vsense signal may be enabled by control circuitry 80. In some examples, sensing event morphological analysis may be used to determine when a suspected VT / VF undersensitivity criterion is met.

[0178] For example, starting when the VTI / VFI counter reaches a low threshold, control circuitry 80 can determine the R-wave pattern matching score for each Vsense signal. The R-wave pattern matching score can be buffered along with other sensing event data determined for each Vsense signal received after the VTI / VFI counter reaches the low threshold. In other examples, the R-wave pattern matching score can be determined for each Vsense signal even before either of the VTI / VFI counters reaches the low threshold. For example, when the VTI / VFI counter reaches 3, control circuitry 80 can begin determining and storing the R-wave pattern matching score for each Vsense signal. The low threshold applied at blocks 308 and 310 can be 5, such that when at least one sensing channel reaches the low threshold, the R-wave pattern matching score of one or more of the most recent previous Vsense signals may already be available for analysis at block 318.

[0179] At block 316, control circuitry 80 determines the R-wave morphological match score, also referred to herein as the “match score,” for each of N Vsense signals received from one or two sensing channels. The N Vsense signals may be the next N Vsense signals received after the VTI / VFI counter of at least one sensing channel 83 or 85 reaches a low threshold. The value of N may be 3, 4, 6, 8, 10, or other specified numbers. In some examples, the N Vsense signals may include one or more Vsense signals that occurred before reaching the low threshold when the morphological match score is available for one or more recent previous Vsense signals. An R-wave template may be previously stored in memory 82 for use in determining the match score. The R-wave template may be established by control circuitry 80 based on a segment of sensing event signal known or possibly normal sinus R waves, according to the morphological signal received from morphological sensing channel 87. Various methods may be used to establish the R-wave template, which may be stored in memory 82 for use in determining the match score.

[0180] Control circuit 80 can determine a matching score at block 316 by buffering cardiac signal segments received from morphological sensing channel 87. When a Vsense signal is received from sensing channel 83 or 85, control circuit 80 can retrieve a segment of sensed event signal that extends before and / or after the timing of the Vsense signal from the morphological signal to determine the matching score. In one example, the sensed event signal segment may extend to 48 samples of a 256Hz sampled morphological signal segment centered on the time of the Vsense signal. Control circuit 80 can perform R-wave morphological matching analysis to obtain a matching score between the sensed event signal segment and a stored R-wave template. Morphological matching techniques may include performing wavelet transform, waveform correlation, or other methods. In one example, the matching score may be in the range of 0 to 100. Various morphological matching techniques can be used to determine the matching score of the sensed event signal segment based on a comparison with a previously established R-wave template (e.g., stored in memory 82).

[0181] At block 318, control circuitry 80 can determine the count of match scores less than a match threshold among N morphological match scores determined for N Vsense signals received from either or both of sensing channels 83 and 85. As an example, the match threshold could be 40, 50, 60, or 70. Match scores greater than or equal to the match threshold indicate a sensed waveform that matches a normal sinus R wave with high confidence. If less than M morphological match scores determined for N Vsense signals received from a given sensing channel 83 or 85 are less than the match threshold (the "No" branch of block 318), control circuitry 80 can determine at block 322 that the suspected VT / VF undersensing criterion is not met. When less than M match scores are less than the match threshold, it means that more than NM match scores are greater than the match threshold, and the Vsense signals associated with match scores greater than the match threshold correspond to a normal sinus R wave and are contraindications to VT / VF. Control circuitry 80 can remain in an indifferent sensing state 1 (see...). Figure 6 In box 120, and without adjusting the sensitivity of sensing channels 83 or 85.

[0182] Referring again to box 318, when at least M of the N matching scores are less than the matching threshold, control circuitry 80 may proceed to box 320 to evaluate N RRIs determined for N Vsense signals from one or two sensing channels 83 and / or 85. In some examples, control circuitry 80 determines the matching score for each of the next 6 Vsense signals received from at least one sensing channel 83 or 85 that has reached a VTI / VFI count greater than or equal to a low threshold. For example, when at least 5 of the 6 matching scores are less than the matching threshold, control circuitry 80 may proceed to box 320 to analyze the RRIs of the 6 Vsense signals. In other examples, at box 318, it may be necessary for at least 70%, 80%, or 90% of the matching scores to be less than the matching threshold.

[0183] At block 320, control circuitry 80 can verify that fewer than a threshold number of RRIs determined for N Vsense signals (whose morphology matching scores have been determined) are VTI or VFI. In one example, fewer than four of the RRIs determined for six Vsense signals received from a given sensing channel 83 or 85 can be counted as VTI or VFI so that control circuitry 80 detects suspected VT / VF undersensing at block 306. If more than X (e.g., four) of the N RRIs are counted as VT / VF intervals (the "No" branch of block 320), the VTI counter and / or VFI counter can trend upward toward NID. In this case, there is no need to trigger GMA or increase sensitivity to avoid VT / VF undersensing because the VTI / VFI counters can reach NID when sensing circuitry 86 operates according to programmed sensitivity. Therefore, if at least X of the N RRIs (e.g., at least 50%, 60%, 70%, or 80% of the N RRIs) are counted as VT / VF intervals (the "No" branch of block 320), the control circuit 80 can determine at block 322 that the suspected VT / VF criterion is not met.

[0184] Generally, suspected VT / VF undersensitivity can be detected when the peak amplitude of the Vsense signal buffer is relatively small (less than a multiple of the effective sensitivity), the R-wave morphology matching score is relatively low (at least M morphology matching scores are less than the matching threshold), and few (if any) RRIs are counted as VT / VF intervals (less than X VT / VF intervals out of N VT / VF intervals, such that VT / VF intervals may be under-counted due to insufficient sensing of low-amplitude R waves or fibrillation waves). According to some examples, the comparisons at boxes 314, 318, and 320 check each of these conditions to detect suspected VT / VF undersensitivity via control circuitry 80.

[0185] exist Figure 8 In the example shown, the control circuit 80 determines at block 306 that a suspected VT / VF insufficiency criterion is met when at least one RRI is greater than or equal to the insufficiency threshold interval (decision block 308), or when criteria applied to the VTI / VFI counter, the magnitude of the sensed event amplitude, the shape match score, and / or the RRI are met (e.g., any combination of decision blocks 304-320). In other examples, one or more requirements associated with the RRI, the peak amplitude of the sensed event, and / or the shape match score, or any combination thereof, may be applied as criteria for determining when a suspected VT / VF insufficiency criterion is met. Figure 8The criteria shown in the decision boxes can be applied in different orders or combinations as shown in flowchart 300, and some decision boxes may be omitted in some examples. For example, when the VTI count or VFI count is greater than a specified threshold and less than the NID of either or both of sensing channels 83 and 85, control circuitry 80 may perform amplitude analysis at boxes 312 and 314, and perform or not perform R-wave morphology matching analysis at boxes 316 and 318. In other examples, morphology analysis may be performed at boxes 316 and 318, and amplitude magnitude analysis may be performed or not at boxes 312 and 314. Any combination of amplitude criteria, RRI criteria, and / or R-wave morphology matching criteria may be applied by control circuitry 80 to buffered sensing event data and / or associated with subsequent Vsense event signals to detect suspected VT / VF undersensing. Other examples of methods that can be used to detect suspected VT / VF insufficiency are generally disclosed in Provisional U.S. Patent Application 63 / 310,558 (Heinks et al.), filed February 15, 2022, the contents of which are incorporated herein by reference in their entirety.

[0186] It should be understood that in some examples, when VT detection is disabled, the process of flowchart 300 is executed to detect suspected VF insufficiency. However, even when VT detection is enabled, the process of flowchart 300 can be executed primarily to detect suspected VF insufficiency, such that at blocks 308 and 310, control circuitry 80 can determine whether the VFI counter for each sensing channel 83 and 85 is at least a threshold (and less than the NID used to detect VF). At block 320, the RRI determined for N Vsense signals can be compared with the VF detection interval to determine when the count has dropped to less than X RRIs from the RRI determined for N Vsense signals.

[0187] When the suspected VT / VF sensing insufficiency criteria are met (as defined in box 306), control circuit 80 may trigger GMA of the cardiac signal segment, as described above. Figure 6 (For example, in) Figure 6 As described in box 124. In some cases, GMA may already be in progress due to suspected long pause detection according to the bradycardia sensing method. In this case, the result of the bradycardia-triggered GMA can be used to respond to the detection of suspected VT / VF insufficiency, rather than necessarily buffering new cardiac signal segments. When cardiac signal segments are classified as VT / VF segments based on GMA, control circuit 80 can increase the sensitivity of one or both of sensing channels 83 and 85, such as Figure 6 As shown in box 122, it continues to buffer at least one or more cardiac signal segments for GMA execution. When the next cardiac signal segment is classified as non-VT / VF or cardiac arrest, control circuit 80 can return to Figure 6The control circuit 80 can disable buffering for cardiac signal segments used in GMA. (Block 120)

[0188] Figure 9 This is a flowchart 350 illustrating a method for performing GMA by control circuitry 80, based on some examples. GMA can be performed in response to a suspected long pause detected by a bradycardia sensing method or in response to a suspected VT / VF insufficiency detected by a tachyarrhythmia sensing method. Figure 6 As shown, the control circuit 80 can respond to the detection of suspected VT / VF sensing insufficiency (e.g., using a combination of...). Figure 8 The described technique is used to trigger the execution of GMA for a cardiac signal segment. As described above, control circuitry 80 can trigger GMA for the cardiac signal segment to be executed in response to the detection of a suspected long pause. Control circuitry 80 can trigger GMA for the cardiac signal segment after the start of the long pause confirmation interval (e.g., after transitioning to re-detection state 5), as described below. Figure 13 As described.

[0189] Once GMA is enabled during irrelevant state 1 in response to a triggering event (such as a suspected long pause detection or a suspected VT / VF insufficiency detection), GMA of flowchart 350 can be repeated for at least one additional cardiac signal segment if the first cardiac signal segment is classified as VT / VF. GMA of flowchart 350 remains enabled when control circuit 80 transitions to any of tachyarrhythmia operating states 2, 3, or 5. Therefore, the process of flowchart 350 can be performed at any time when control circuit 80 requires the results of GMA for bradycardia sensing and pacing control and / or for VT / VF detection and for controlling CV / DF shock therapy.

[0190] At block 351, control circuitry 80 acquires a cardiac signal segment for performing GMA. The cardiac signal segment may be received from morphological signal channel 87. The cardiac signal segment may be at least one second long, and in various examples may be 1.5 to 6 seconds long. In an exemplary example, the cardiac signal segment is 3 seconds long and its start point is independent of the timing of the Vsense signal, because no Vsense signal may be received, for example, if a long pause in ventricular activity is occurring or VT / VF sensing is insufficient.

[0191] GMA of a cardiac signal segment differs from R-wave morphology matching or other morphological analysis of a sensed event signal segment associated with a Vsense signal due to R-wave threshold exceeding. R-wave morphology matching or other morphological analysis of the sensed event signal segment is performed on the acquired sensed event signal segment having a start and end time that is timing-dependent on the Vsense signal and is intended to cover, for example, an R-wave or QRS waveform. The cardiac signal segment obtained for GMA at box 351 can be relatively long compared to the length of the cardiac cycle, for example, greater than the VT or VF detection interval, and therefore may include multiple VT or VF cycles when VT / VF is present. Therefore, GMA can be performed on cardiac signal segments with start and end times that do not necessarily cover the Vsense signal (because the Vsense signal may not have been received). GMA can be performed to evaluate the frequency components of the cardiac signal segment to indicate relatively high-frequency VT / VF cycles that may be present in the cardiac signal segment, without knowing the relative timing of the VT / VF cycles or the R-wave or fibrillation wave.

[0192] At block 352, control circuitry 80 can determine an amplitude quantity based on a cardiac signal segment. The amplitude quantity can be determined by identifying signal peaks in the cardiac signal segment and determining the representative amplitude of the identified signal peaks. In some examples, control circuitry 80 can determine a first-order derivative signal based on the cardiac signal segment, which can be estimated as a first-order differential signal by determining the difference between consecutive sampling points of the cardiac signal segment. The derivative signal can be rectified to facilitate analysis of the cardiac signal segment to identify signal peaks. In some examples, a gradient signal is determined based on a morphological signal received from morphological signal channel 87, which can then be bandpass filtered before determining the rectified differential signal based on the cardiac signal segment.

[0193] Control circuit 80 can identify signal peaks in the rectified differential signal that are greater than a signal pulse amplitude threshold and separated from other signal peaks by at least a threshold time interval. For example, starting from the beginning of a cardiac signal segment, the first earliest signal pulse greater than the signal pulse amplitude threshold can be identified. The next earliest signal pulse, greater than the signal pulse amplitude threshold and having a peak at least 100 ms later than the first signal pulse peak, can be identified, and so on. In this way, the next earliest signal pulse at least 100 ms after the most recently identified signal pulse is identified as a signal pulse. In other examples, if more than one signal pulse peak greater than the signal pulse amplitude threshold occurs within 100 ms of each other, then the signal pulse peak with the largest amplitude can be identified as the signal pulse peak, and other signal pulse peaks within 100 ms of the identified signal pulse peak can be ignored. In this way, a single R wave or fibrillation wave that may have more than one peak will not be identified twice.

[0194] The control circuit 80 can determine the signal pulse amplitude threshold as a percentage of the average of the local maximum amplitudes of multiple sub-segments of a cardiac signal segment, for example, 15% to 50% or about one-sixth to one-half. In an exemplary example, the control circuit 80 can determine the local maximum peak amplitude of each of the four sub-segments of a 3-second cardiac signal segment. The control circuit 80 can determine the signal pulse amplitude threshold as one-third of the average amplitude of the four local maximum amplitudes.

[0195] At block 352, control circuitry 80 determines the amplitude amount based on the identified signal pulses. Control circuitry 80 determines the amplitude amount by determining the average, median, maximum, minimum, range, and / or standard deviation, or other representative values ​​of the peak amplitudes of signal pulses identified as being greater than a signal pulse amplitude threshold and at least separated by a minimum time interval. At block 354, control circuitry 80 compares the amplitude amount to an amplitude threshold. As an example, the amplitude threshold may be between 0.05 mV and 0.2 mV. In one example, the amplitude threshold is 0.1 mV, but other thresholds may also be applied to the amplitude amount. The amplitude threshold may be based on the minimum expected amplitude of a fibrillation wave. The amplitude threshold may be referred to as the "cardiac arrest amplitude threshold" because it represents the minimum amplitude of a cardiac signal segment, such as an R wave or fibrillation wave, when ventricular activity is present. When the amplitude amount is less than the amplitude threshold, ventricular cardiac arrest may occur. When the amplitude is less than the amplitude threshold (the "Yes" branch of box 354), the control circuit 80 may perform a first analysis of the cardiac signal segment at box 356 to determine whether the cardiac arrest criteria are met. When the amplitude is greater than (or equal to) the amplitude threshold (the "No" branch of box 354), the control circuit 80 may perform a second analysis of the cardiac signal segment at box 360 to determine whether the VT / VF criteria are met.

[0196] The cardiac arrest analysis performed at box 356 typically includes identifying at least a specified portion of a cardiac signal segment whose amplitude variation consistently falls within the cardiac arrest range. During cardiac arrest, the cardiac signal segment is expected to be relatively flat with a low degree of signal variability. The cardiac arrest analysis of the cardiac signal segment may include determining a signal stability measure representing the degree of signal variability present in the cardiac signal segment. In some examples, the signal stability measure may be determined as a count of the number of moving windows in the cardiac signal segment during which fewer than a threshold number of sampling points of the signal segment fall outside the cardiac arrest amplitude range, for example, greater than or less than the cardiac arrest amplitude range.

[0197] At block 356, control circuitry 80 determines a low-pass filtered signal to smooth a segment of cardiac signal. Signal smoothing by averaging or filtering produces a relatively flat signal in the absence of ventricular activity and enhances any ventricular activity signal relative to attenuated noise that may be present in the cardiac signal segment. Control circuitry 80 can be configured to determine the low-pass filtered signal based on broadband and notch-filtered cardiac signals received from morphological signal channel 87. In some examples, a bandpass filter can be applied to broadband and notch-filtered cardiac signals received from morphological signal channel 87 and used to determine when cardiac arrest criteria are met. Control circuitry 80 can determine a gradient signal based on the low-pass filtered signal. In some examples, the gradient signal can be generated using a center-difference method, for example, by determining the difference between sample points i+1 and i-1 and dividing by 2. In this way, a signal representing the gradient or rate of change of the low-pass filtered cardiac signal segment is determined. In other examples, forward-difference or backward-difference methods can be used.

[0198] When (e.g., a gradient signal) cardiac signal sampling points remain within the cardiac arrest range for at least a specified number of sampling points or a specified cumulative time interval (which may be all or part of the cardiac signal segment), control circuit 80 can determine whether the cardiac signal segment meets the cardiac arrest criteria. When cardiac arrest is present, the gradient signal is expected to be a substantially flat signal with small fluctuations. If cardiac arrest is not present, ventricular activity will cause fluctuations in the gradient signal that exceed the cardiac arrest range. When the gradient signal exceeds the cardiac arrest range for a threshold number of sampling points, control circuit 80 can determine that the cardiac signal segment is not a cardiac arrest segment. When the gradient signal is within the cardiac arrest range for at least a threshold number of sampling points (or a predetermined time interval) out of a specified number of consecutive or discontinuous sampling points, control circuit 80 can determine that a persistent cardiac arrest state exists and classify the cardiac signal segment as a cardiac arrest segment.

[0199] In some examples, control circuit 80 may determine that the cardiac arrest criterion is met at block 356 when at least Y consecutive sliding windows of Z sampling points of a cardiac signal segment include at least X sampling points of the gradient signal falling within the cardiac arrest range. In an exemplary example, control circuit 80 may determine that the cardiac arrest criterion is met at block 356 when at least 5 sampling points of the 21 sampling points of the gradient signal fall within 100 to 700 consecutive sliding windows of the cardiac arrest range, or fall within other portions of the cardiac signal segment or a certain number of sampling points. Control circuit 80 may classify the cardiac signal segment as a cardiac arrest segment at block 358 in response to the cardiac arrest criterion being met at block 356. When the cardiac arrest criterion is not met at block 356, control circuit 80 may classify the cardiac signal segment as non-VT / VF at block 362.

[0200] Referring again to box 354, when control circuit 80 determines that the amplitude is not less than an amplitude threshold, the signal pulse identified at box 352 for determining the amplitude may correspond to ventricular activity, such as an R wave or fibrillation wave. At box 360, control circuit 80 may determine whether a cardiac signal segment meets the VT / VF criteria. Control circuit 80 may determine one or more morphological measures based on the cardiac signal segment to detect evidence of VT / VF. The morphological measures determined based on the cardiac signal segment can distinguish between true VT / VF rhythms and non-VT / VF rhythms, which may include supraventricular tachycardia, rapidly conducting atrial fibrillation, or oversensing of P waves, T waves, and / or non-cardiac noise. The morphological measures may be determined based on sampling points spanning the entire cardiac signal segment and are independent of the time period during which the cardiac signal segment includes the Vsense signal received from sensing channels 83 or 85. In some cases, the Vsense signal may not be received from sensing circuit 86 during the analysis of the cardiac signal segment for VT / VF detection.

[0201] As described above, cardiac signal segments can be received from morphological signal channel 87 and can be bandpass and notch-filtered signals. In some examples, the cardiac electrical signal is filtered, for example, using a 2Hz to 40Hz bandpass filter, a 3Hz to 32Hz bandpass filter, or a 4Hz to 30Hz bandpass filter. Control circuitry 80 can determine a gradient signal and / or a bandpass-filtered signal based on the signal received from morphological signal channel 87, and subsequently determine a first-order differential signal, which is rectified for use in determining VT / VF morphological metrics based on the cardiac signal segments.

[0202] One morphological measure associated with the frequency components of the cardiac signal segment, which can be determined by control circuit 80, is the mean time interval (MP). MP can be calculated as the reciprocal of the mean frequency of the cardiac signal segment, which is an estimate of the center frequency of the cardiac signal segment. The mean frequency can be determined by control circuit 80 as the ratio of the mean absolute amplitude of the rectified first-order differential signal (the sum of the amplitudes of all sampled points of the rectified differential signal divided by the total number of sampled points) to the mean absolute amplitude of the rectified cardiac signal segment (the sum of the amplitudes of all sampled points of the rectified cardiac signal segment divided by the total number of sampled points). Therefore, MP can be estimated as the ratio of the sum of the amplitudes of all sampled points of the rectified cardiac signal segment to the sum of the amplitudes of all sampled points of the rectified first-order differential signal. MP can optionally be converted to a radian measure by multiplying this ratio by a factor of 2π / (sampling frequency).

[0203] In some examples, control circuitry 80 may use MP at block 360 to determine the spectral width (SW). Control circuitry 80 may determine SW as the fundamental time period of the cardiac signal segment minus MP. In some examples, control circuitry 80 may determine the fundamental time period as the average of the peak intervals determined between the signal peaks identified at block 352 as described above. In some examples, the fundamental frequency may be determined as a truncated mean, for example by removing one or more longest peak intervals and / or one or more shortest peak intervals between the signal peaks identified from the rectified differential signal determined according to the cardiac signal segment. SW can then be determined by control circuitry 80 by subtracting MP from the fundamental time period.

[0204] In some examples, control circuitry 80 determines when the VT / VF criterion is met based on SW and MP. In some examples, control circuitry 80 may compare the ratio of SW to MP with a threshold. For example, when MP is at least 60 ms and the SW / MP ratio is less than or equal to 0.1, a cardiac signal segment may be classified as a VT / VF segment at box 364. In another example, when MP is at least 65 and the SW / MP ratio is less than or equal to a variable threshold that can be defined as a function of MP, a cardiac signal segment may be classified as a VT / VF segment at box 364. In an exemplary example, the SW / MP ratio may be compared with a linear function of MP given by the equation {-0.0035*(MP)+0.145}. When the SW / MP ratio is less than or equal to this variable threshold that is determined to be a function of MP, a cardiac signal segment may be classified as a VT / VF segment at box 364. Other coefficients and constants can be used to define a variable threshold as a function of a morphological metric (e.g., MP), which is applied to another morphological metric or the mathematical relationship between two or more morphological metrics (e.g., the SW / MP ratio).

[0205] Variable thresholds, defined as functions of morphological measures, can be tailored to individual patients or optimized based on data from patient populations to classify cardiac signal segments into VT / VF with high sensitivity and / or specificity. Other thresholds can be defined based on the duration of the cardiac signal segment for morphological measures that reliably distinguish VT / VF segments from non-VT / VF segments based on MP and SW / MP ratios.

[0206] The VT / VF criterion applied to the morphological measure at box 360 may depend on the duration of the cardiac signal segment and / or the tachyarrhythmic operating state of the ICD 14. In one example, when the ICD 14 operates in irrelevant sensing state 1 and triggers GMA in response to the detection of a suspected long pause or a suspected VT / VF insufficiency, the control circuit 80 may apply a threshold different from the threshold applied during the relevant state 2 of the tachyarrhythmic detection state to the MP and SW / MP ratios. For example, when the ICD 14 operates in irrelevant state 1, the control circuit 80 may determine at box 360 that the VT / VF criterion is met when MP is at least 60 and the SW / MP ratio is less than or equal to 0.1. When the ICD 14 operates in relevant state 2 (or other higher tachyarrhythmic operating state), the control circuit 80 may determine at box 360 that the VT / VF criterion is met when MP is at least 65 and the SW / MP ratio is less than or equal to -0.0035*MP+0.145. When MP and SW do not meet the VT / VF criteria applied at box 360, cardiac signal fragments can be classified as non-VT / VF at box 362.

[0207] Combined with the following text Figure 14 As described, during post-shock pacing (or bradycardia pacing after a long pause detection), GMA can be performed using relatively short cardiac signal segments (e.g., 0.5-second segments) that can be acquired between delivered pacing pulses. For example, when the cardiac signal segment is only 0.5 seconds long instead of 3 seconds, as an illustrative example, when MP is at least 60 and the SW / MP ratio is greater than -1 and less than or equal to 0.085, control circuitry 80 can classify the cardiac signal segment as a VT / VF segment. Therefore, although the process of flowchart 350 can be performed whenever a GMA result is required according to the tachyarrhythmia sensing method and / or bradycardia sensing method, the criteria applied to the morphological measure determined based on the cardiac signal segment may vary depending on the tachyarrhythmia operating state and / or bradycardia operating state of control circuitry 80.

[0208] In other examples, the low-slope component (LSC) and / or one or more noise metrics (such as muscle noise pulse count, average rectified area, normalized average rectified area) may be determined by control circuitry 80 as morphological metrics to determine at block 360 when the VT / VF criterion is met. The low-slope component can be determined by summing all samples of the rectified differential signal with amplitudes less than or equal to the low-slope amplitude threshold and dividing the sum by the total number of samples in the cardiac signal segment.

[0209] In some examples, LSC, MP, and / or SW can each be compared to a corresponding threshold used to classify a cardiac signal segment as a VT / VF segment or a non-VT / VF segment. In an exemplary example, when MP is at least 60 ms, SW is less than or equal to 10 ms, and LSC is less than or equal to 0.7 (70%), control circuitry 80 can determine at block 364 that the cardiac signal segment is a VT / VF segment. When MP is less than 60 ms, or SW is greater than 10 ms, or LSC is greater than 0.7, control circuitry 80 can determine at block 362 that the cardiac signal segment is a non-VT / VF segment.

[0210] In some examples, control circuitry 80 may determine a heart rate estimate as a morphological measure at block 360. A peak interval measure may be determined as the average, median, or other representative value of the peak intervals determined between the peaks of the signal pulses identified at block 352 as described above. The peak interval measure may be correlated with the rate of any ventricular event signal in the cardiac signal segment and provides evidence for classifying the cardiac signal segment as VT / VF in the absence of or without a Vsense signal from sensing circuitry 86. In some examples, control circuitry 80 may determine a count of signal peaks identified in the cardiac signal segment. Based on the method for identifying signal peaks described above in conjunction with block 352, the identified signal peaks are at least separated by a threshold time interval. Based on the duration of the cardiac signal segment, the count of identified signal peaks may be an indication of the average rate of the signal pulses during the cardiac signal segment. In some examples, a heart rate estimate based on a peak interval measure or the count of identified signal pulses may be compared at block 360 with a VT / VF rate criterion for classifying the cardiac signal segment as VT / VF or non-VT / VF.

[0211] The combination of MP and SW / MP ratio, as a morphological metric for distinguishing between VT / VF and non-VT / VF segments, can reliably and with high sensitivity classify VF segments without requiring determination of LSC, heart rate estimation metrics, or noise metrics based on the cardiac signal segment. However, it should be recognized that numerous criteria are conceivable for distinguishing between VT / VF and non-VT / VF segments using multiple combinations of LSC, MP, SW, one or more heart rate estimation metrics, and / or one or more noise metrics. Such combinations may include mathematical combinations of two or more metrics (e.g., SW / MP ratio). The VT / VF criteria applied by control circuitry 80 at block 360 may include one or more thresholds applied to the respective metric or mathematical combination of metrics, where each threshold may be defined as a constant or function (e.g., a linear function) of the metric determined based on the cardiac signal segment. Other examples of performing GMA to classify cardiac signal fragments as cardiac arrest, VT / VF, or non-VT / VF are generally disclosed in U.S. Patent No. 18 / 045,135 (Aranda Hernandez et al.), filed October 7, 2022 (the entire contents of which are incorporated herein by reference) and U.S. Patent No. 63 / 310,558 (Heinks et al.), which is also incorporated herein by reference.

[0212] When the VT / VF criteria are met at box 360, the cardiac signal segment is classified as a VT / VF segment at box 364. Control circuit 80 can restart the long pause detection interval to avoid cardiac pacing performed by treatment delivery circuit 84, which may interfere with or delay the detection of VT / VF episodes. When control circuit 80 is in irrelevant sensing state 1 (… Figure 6 During operation, control circuit 80 may increase the sensitivity of sensing circuit 86, for example, by adjusting the sensitivity of both sensing channels 83 and 85 to a lower or minimum available voltage amplitude setting in response to VT / VF classification. Control circuit 80 may continue to perform GMA on one or more subsequent cardiac signal segments until at least one cardiac signal segment is classified as cardiac arrest or non-VT / VF. If the cardiac signal segment is classified as VT / VF and is the Nth VT / VF segment required for a forced transition to relevant state 2, and at least one VTI / VFI counter has reached the threshold percentage of NID, then control circuit 80 may transition from irrelevant state 1 to relevant state 2 (see [link to relevant state 2]). Figure 5 and Figure 6 If a cardiac signal segment is classified as VT / VF at box 364 and is the Nth VT / VF segment classified as VT / VF when all VTI / VFI counters are less than the threshold, then control circuit 80 may transition from box 122 to box 120 of the unrelated sensing state 1 of the tachyarrhythmia operating state (see box 120). Figure 6 ).

[0213] When the VT / VF criterion is not met at frame 360, the control circuit 80 may classify the cardiac signal segment as non-VT / VF. When a first GMA executed in response to a suspected long pause detection results in a non-VT / VF or cardiac arrest classification, the control circuit 80 may deliver at least one pacing pulse upon confirmation of the long pause. When a first GMA executed in response to a suspected VT / VF insufficiency detection results in a non-VT / VF classification, the sensing circuit 86 may... Figure 6 The irrelevant sensing state 102 in box 124 returns to box 120. Sensing circuitry 86 can continue sensing ventricular event signals according to the programmed sensitivity of each sensing channel 83 and 85. GMA can be disabled unless needed for other bradycardia or tachyarrhythmia sensing purposes. (The above is combined with...) Figure 6 And the following text combines Figures 10 to 14 The paper further describes these and other responses to cardiac signal fragment classification based on GMA performed according to flowchart 350.

[0214] Figure 10 This is a flowchart 400 based on some examples of methods for detecting VT / VF, which can be combined with ICD 14 above. Figure 5 The method is executed during state 2, which describes the operational state of tachyarrhythmias. At box 402, when the above conditions are met... Figure 5 Upon any of the described transition criteria, control circuit 80 transitions to state 2, the suspected state of a tachyarrhythmia. If cardiac segment buffering and GMA are not already in progress, control circuit 80 may enable cardiac segment buffering and GMA at block 404. In some cases, when programmed sensitivity is valid, a transition to state 2 occurs in response to satisfying NID. In this case, GMA may not be enabled or may not be in progress after transitioning to state 2, and it may be enabled at block 404.

[0215] In other cases, it can be combined with the above. Figure 6 GMA is enabled during the described irrelevant state 1, for example, due to the combination of Figure 8 The described suspected VT / VF sensing insufficiency, or suspected long pauses due to bradycardia sensing methods, occurs when a transition to relevant state 2 occurs with increased ventricular sensitivity (e.g., in situations such as...). Figure 6 As shown in the diagram and described above (box 122), buffering of cardiac signal fragments for GMA may have been enabled and may remain enabled after transitioning to relevant state 2.

[0216] At block 406, control circuitry 80 determines whether sensing channel 83 or 85 meets NID, which sensing channel is selected for reliable sensing of VT / VF detection, as described above. Figure 7As described. In some cases, NID is satisfied after transitioning to relevant state 2. In other cases, if the threshold number of cardiac signal fragments has already been classified as VT / VF based on GMA enabled during the irrelevant sensing state, then when control circuit 80 transitions to relevant state 2, a percentage of NID can be reached, but not the full value of NID (see [link to relevant state 2]). Figure 6 (arrow 130). If NID is not met, control circuit 206 can determine whether the termination criterion is met at box 414. If the termination criterion is not met after transitioning to state 2, control circuit 80 returns to box 406 and waits for NID to be reached or the termination criterion to be met, whichever comes first.

[0217] If the termination criterion is met at box 414, for example, based on the above... Figure 5 In any of the examples described, control circuitry 80 may transition back to indifferent state 1 at block 416. Upon transitioning back to indifferent sensing state 1, sensitivity may be restored to the programmed sensitivity (if previously increased), and GMA may be disabled. The VTI / VFI counter may be reset to zero. Control circuitry 80 may, for example, according to... Figure 6 The method executed at block 120 counts the VT / VF interval based on the Vsense signal received from both sensing channels 83 and 85.

[0218] If NID is reached at box 406 before the termination criterion is met at box 414, control circuit 80 can determine at box 408 whether the rejection rule is met. When NID is reached, resulting in a transition to the relevant state 2, control circuit 80 can advance the direction to box 408 to determine whether the rejection rule is met. (As mentioned above...) Figure 7 As generally described, control circuitry 80 can determine sensing event data corresponding to a Vsense signal received from a selected sensing channel. At block 408, the sensing event data can be further determined and stored for determining whether a rejection rule is met. One or more rejection rules can be applied to the sensing event data to determine when oversensing of cardiac signals (e.g., P waves or T waves are incorrectly sensed as R waves), oversensing of non-cardiac signals (e.g., skeletal muscle electrophysiological signal pulses or electromagnetic interference are incorrectly sensed as R waves), and / or conducted SVT may occur. When rejection rules are met based on various criteria applied to the sensing event data, VT / VF detection based on satisfying NID can be suppressed. The following example combines... Figure 11 and Figure 12 The flowchart illustrates an example of a method that can be executed by control circuit 80 to determine when a rejection rule is met.

[0219] When NID is satisfied but the rejection rule is not met (the "No" branch of block 408), control circuit 80 can proceed to block 418. Control circuit 80 can detect VT / VF and transition to charging state 3. Figure 5 (As shown). If control circuit 80 determines at block 408 that a rejection rule is satisfied, control circuit 80 may determine at block 410 whether the satisfied rejection rule is overridden by the GMA result of VT / VF. When the GMA result is VT / VF, the rejection rule used to suppress VT / VF detection may be overridden, allowing control circuit 80 to still detect VT / VF. In some examples, multiple rejection rules may be applied by control circuit 80, such as T-wave oversensing rejection rules, P-wave oversensing rejection rules, one or more noise rejection rules (e.g., for rejecting oversensing of EMI or skeletal muscle noise impulses), and / or one or more SVT rejection rules (e.g., for rejecting sinus tachycardia or fast-conduction atrial fibrillation). For example, one or more rejection rules may be satisfied or “triggered” when a corresponding rejection rule is determined to be true based on criteria applied by control circuit 80 to the sensed event data. Some, but not all, of the rejection rules may be overridden as a GMA result of VT / VF. Therefore, in some cases, the excitation rejection rule may take precedence over the GMA result satisfying both NID and VT / VF, thus suppressing VT / VF detection at block 412. In other cases, when the excitation rejection rule can be overridden by the GMA result and the current or most recent GMA result is VT / VF, the control circuit 80 may ignore or disregard the rejection rule. The control circuit 80 may detect VT / VF at block 418.

[0220] When a rejection rule is met, one or more rejection rules applied at block 408 can be overridden by the GMA result of VT / VF. Therefore, if a GMA result is available when NID is met and a rejection rule is determined to be met, control circuitry 80 can determine whether the GMA result is VT / VF. In various examples, the GMA result may need to be less than 0.5 seconds, 0.75 seconds, or 1 second. For example, if the GMA result is determined more than 1 second before a rejection rule is triggered, the GMA result may not be used to overridden the rejection rule. At block 412, VT / VF detection can be suppressed, and control circuitry 80 can return to block 406. If the GMA result is determined within 1 second (or other specified time interval) before a rejection rule is triggered, control circuitry 80 can use the GMA result of VT / VF to overridden the rejection rule. The GMA result of VT / VF, combined with the achievement of NID, allows control circuitry 80 to detect VT / VF at block 418 and transition to charging state 3, even if a rejection rule has been met.

[0221] In some examples, GMA results may be unavailable when a rejection rule is triggered. In some examples, to avoid unnecessary CV / DF shocks, control circuitry 80 may wait for the buffering of cardiac signal segments and the processing required to classify cardiac signal segments as VT / VF, non-VT / VF, or cardiac arrest to complete. Therefore, if GMA results are unavailable when a rejection rule is met, control circuitry 80 may suppress VT / VF detection at block 412 and return to block 406. Control circuitry 80 may continue to update the VTI / VFI counter to determine whether the NID is met using each received Vsense signal. Control circuitry 80 may apply termination criteria to the RRI using each received Vsense signal. Control circuitry 80 may continue to determine sensed event data and any other signal analysis required, such as for updating the state of the rejection rule applied at block 408.

[0222] If the NID and rejection rule are still met at box 408 when the GMA result becomes available, then if the cardiac signal segment is classified as cardiac arrest or non-VT / VF based on the GMA, the control circuit 80 may continue to suppress VT / VF detection at box 412. The control circuit 80 may return to box 406. However, if the cardiac signal segment is classified as VT / VF based on the GMA, the rejection rule may be overridden. The control circuit 80 may detect VT / VF at box 418 and transition to charging state 3 in response to meeting the NID and the VT / VF classification of the cardiac signal segment. It should be understood that at any time during the process of performing the GMA and determining whether the rejection rule is met, the control circuit 80 may determine that the termination criterion (box 414) is met and return to irrelevant state 1 before detecting VT / VF.

[0223] Figure 11 This is a flowchart 450 of a method, according to some examples, that can be executed by control circuitry 80 to determine when a cardiac event oversensing (OS) rejection rule is met. In this example, the applied cardiac event oversensing rejection rule is the P-wave oversensing (PWOS) rejection rule. PWOS occurs when the P wave of the cardiac electrical signal exceeds the R-wave sensing threshold, causing the selected sensing channel 83 or 85 to generate an erroneous Vsense signal that is transmitted to control circuitry 80. However, it should be understood that, in conjunction with... Figure 11 The described technique for detecting cardiac events OS can be applied to other types of oversensing, such as T-wave oversensing.

[0224] At block 452, control circuitry 80 receives the Vsense signal (e.g., as combined with) from a sensing channel selected as a reliable sensing channel for VT / VF detection. Figure 7(As described). At block 454, control circuitry 80 may determine one or more signal features from a segment of sensing event signal buffered in memory 82 in response to a Vsense signal. Sensing event data may include features determined from cardiac electrical signals sensed by sensing channels 83 or 85 selected for VT / VF detection after transition to relevant state 2. For example, the maximum peak value of the rectified cardiac electrical signal after an R-wave sensing threshold exceedance and / or the peak-to-peak amplitude of the selected sensing channel signal during the R-wave peak tracking period or the post-sensing blanking period may be determined by sensing circuitry 86 or control circuitry 80 after an R-wave sensing threshold exceedance corresponding to the Vsense signal. Sensing event data may include an RRI determined for the received Vsense signal.

[0225] The sensing event data determined at block 454 may include features determined from the morphological signal received by morphological signal channel 87. For example, the R-wave morphological matching score may be determined by control circuitry 80 and stored together with the sensing event data for the Vsense signal. The sensing event data may be buffered in memory 82, for example, for at least 3 to 24 of the most recent Vsense signals, such that the sensing event data can be used to determine when a rejection rule is met. It is anticipated that the sensing event data buffered in memory 82 may be determined for the Vsense signal received from the selected sensing channel 83 or 85 before and / or after transitioning to correlated state 2, for determining whether a rejection rule is met in response to reaching NID.

[0226] Other examples of sensed event data that can be buffered for determining whether the PWOS rejection rule is satisfied may include the polarity (positive or negative) of the maximum absolute peak amplitude. In yet another example, the signal feature determined at box 454 may be the maximum slope, total area (e.g., the integral or sum of the amplitudes at the sampling points), or other features of the sensed event signal segment received from morphological signal channel 87. When the Vsense signal generated by the selected sense channel 83 or 85 corresponds to an alternating pattern of R-waves and P-waves (e.g., PRP or RPR), any signal features that are expected to alternate due to the alternating R-waves and oversensitized P-waves may be determined and stored as sensed event data of a continuous Vsense signal. In some examples, two or more signal features may be determined from each sensed event signal segment to detect an alternating pattern of combinations of two or more signal features.

[0227] At block 456, control circuitry 80 can compare sensing event data determined for continuously received Vsense signals (e.g., three continuously received Vsense signals) with each other to detect alternating patterns of signal characteristics. The sensing event data can also be compared with criteria used to identify the true R-wave in an oversensitized P-wave. For example, alternating patterns of relatively high and relatively low maximum peak amplitudes can be detected at block 456. The peak amplitude can be a value determined by sensing circuitry 86 during the R-wave peak tracking period and transmitted to the R-wave detector (…). Figure 4 The peak amplitude is the maximum peak value of the rectified signal (66a or 66b) in the above example. In other examples, the peak amplitude may be the maximum peak-to-peak amplitude of the unrectified signal sensed by the sensing circuit 86 (e.g., by the selected sensing channel 83 or 85 or by the morphological signal channel 87) during the post-sensing blanking period after the Vsense signal.

[0228] For illustrative purposes, the maximum peak amplitudes determined for three consecutive Vsense signals may be referred to as A1, A2, and A3. A3 may be the peak amplitude corresponding to the most recent (e.g., the i-th) Vsense signal. A2 may be the peak amplitude of the most recent preceding (e.g., i-1) Vsense signal. A1 may be the peak amplitude of i-2 Vsense signals. The alternation pattern of the maximum peak amplitudes may be determined by the control circuit 80 by determining a first amplitude difference D1 between amplitudes A1 and A2, for example, D1 = A2 - A1. A second amplitude difference D2 may be determined between the second amplitude A2 and the third amplitude A3, for example, D2 = A3 - A2. The first amplitude difference D1 and the second amplitude difference D2 between the three consecutively determined maximum peak amplitudes A1, A2, and A3 may be compared with a difference threshold to detect an alternation pattern of high-low-high or low-high-low maximum peak amplitudes associated with the Vsense signals.

[0229] The difference threshold can be a fixed value or set based on at least one of the determined peak amplitudes A1, A2, or A3. In some examples, the difference threshold can be set as a percentage of one of the two amplitudes being compared (e.g., a percentage of A1 or A2 used for comparison with D1 and a percentage of one of A2 or A3 used for comparison with D2). The percentage of peak amplitude applied by control circuit 80 as the difference threshold can be 15% to 35% of one of the peak amplitudes being compared. In some examples, the difference threshold is 22% to 25% of one of the peak amplitudes being compared.

[0230] In an exemplary example, control circuit 80 may compare D1 with 25% of A2 and D2 with 25% of A1. Control circuit 80 may compare D2 with 25% of A3 and D2 with 25% of A2. When the negative value of the difference D1(A2-A1) is greater than 25% of A1 and the negative value of the difference D2(A3-A2) is greater than 25% of A3, control circuit 80 may detect a high-low-high alternating pattern of three consecutive peak amplitudes. When the difference D1(A2-A1) is greater than 25% of A2 and the negative value of the difference D2(A3-A2) is greater than 25% of A2, control circuit 80 may detect a low-high-low alternating pattern of three consecutive peak amplitudes. It should be appreciated that other criteria may be conceived and applied for detecting alternating patterns of high-low-high or low-high-low peak amplitudes of three consecutive sensed event signals.

[0231] The detection of alternating patterns of high-low-high or low-high-low peak amplitudes corresponding to PWOS may further require that the sensed event signal segment buffered in response to the peak amplitude of the high-amplitude event identified by the comparative analysis of D1 and D2 has an R-wave morphology matching score greater than a matching threshold. For example, when the amplitude criteria applied to D1 and D2 indicate a high-low-high pattern, the control circuit 80 may determine whether the R-wave morphology matching score determined for the first Vsense signal (corresponding to A1) and / or the third most recent Vsense signal (corresponding to A3) is greater than the matching threshold. The R-wave morphology matching score (also referred to herein as the "morphology matching score") may be determined between the sensed event signal segment buffered from the morphology signal channel 87 and the R-wave template stored in the memory 82, as described above. Figure 8 As generally described, when the amplitude criteria applied to D1 and D2 indicate a low-high-low pattern, control circuit 80 can determine whether the R-wave morphological matching score determined for the second Vsense signal (corresponding to A2) is greater than a matching threshold. This matching threshold can be 40%, 50%, 60%, 70%, or other specified thresholds. Alternatively or additionally, the morphological matching score stored for the Vsense signal corresponding to a low peak amplitude (A2 in the high-low-high pattern or A1 and / or A3 in the low-high-low pattern) may need to be less than the matching threshold, for example, less than 10%, 20%, 25%, 30%, 35%, or 40%.

[0232] In other examples, alternating patterns of event signal polarity can be detected at block 456. In yet another example, the alternating pattern detection criteria applied by control circuitry 80 at block 456 may require a long-short RRI pattern when the amplitude pattern is high-low-high or a short-long RRI pattern when the amplitude pattern is low-high-low. In yet another example, at block 456, it may be necessary to sense patterns of low-high-low or high-low-high maximum slope of the event signal for detecting alternating patterns of cardiac event signals. In the exemplary examples described herein, control circuitry 80 is described as analyzing three consecutively sensed event signals for detecting alternating patterns of signal characteristics in high-low-high or low-high-low patterns. However, it is contemplated that two consecutively sensed event signals may be analyzed for detecting low-high or high-low patterns, or more than three consecutively sensed event signals may be analyzed for detecting alternating patterns (e.g., high-low-high-low or low-high-low-high, etc.).

[0233] Other sense event data that can be determined at box 454 for a given Vsense signal may include the normalized rectified amplitude and / or maximum pulse width of the sense event signal segment received from morphological signal channel 87. The normalized rectified amplitude and / or pulse width may be compared to criteria used to identify the sense event signal waveform as a true VT / VF waveform rather than an oversensitized P-wave. In some examples, when the normalized rectified amplitude and / or maximum pulse width meet the true VT / VF waveform criteria, no alternation pattern of the sense event data is detected at box 456.

[0234] exist Figure 11 In the example, if the amplitude criterion or R-wave morphology matching criterion for detecting the alternating pattern of the sensed event signal is not met at box 456, the control circuit 80 may return to box 452 to wait for the next Vsense signal. The PWOS rejection rule may still not be met. When the control circuit 80 detects a high-low-high or low-high-low alternating pattern of the sensed event signal based on peak amplitude analysis and R-wave morphology matching score analysis at box 456, the control circuit 80 may detect evidence of PWOS based on the alternating pattern. However, the control circuit 80 may determine at box 460 whether the most recent GMA result is VT / VF. If the most recent GMA result is VT / VF, then the GMA result may override the PWOS rejection rule. In this example, the control circuit 80 may return to box 452 (the "Yes" branch of box 460) without incrementing the OS evidence counter at box 464. Due to the GMA result, the PWOS rejection rule may still not be met.

[0235] When the most recent GMA result is not VT / VF, for example, when the most recent cardiac signal segment is classified as cardiac arrest or non-VT / VF, the control circuit 80 may increment the OS evidence counter at block 464 based on the alternating pattern of the sensed event signal detected at block 456. The control circuit 80 may increment the OS cardiac event evidence counter by 1, or mark the most recent Vsense event signal and the corresponding sensed event data as PWOS evidence, so that the control circuit 80 can track the number of times the alternating pattern of cardiac event oversensing is identified without being overridden by the GMA result being VT / VF.

[0236] At box 466, control circuitry 80 can compare the value of the OS evidence counter with a threshold used to detect cardiac event oversensing (in this case, PWOS). If the OS evidence counter has reached the threshold, meaning that at least the most recent GMA result is not VT / VF, the OS rejection rule or "fire" is satisfied at box 470. For example, the threshold applied to the OS evidence counter could be 3, 4, 5, or 6 Vsense signals out of the most recent 8, 10, 12, 20, or 24 Vsense signals. In one example, when 3 out of 12 Vsense signals out of the most recent Vsense signals are flagged as evidence of PWOS, control circuitry 80 can determine at box 466 that the OS evidence counter has met the threshold and at box 470 that the PWOS rejection rule is satisfied without being overridden based on GMA. If the VTI / VFI counter associated with the selected sensing channel 83 or 85 has reached NID, VT / VF detection can be suppressed in response to satisfying the PWOS rejection rule and without being overridden based on the most recent GMA.

[0237] If the OS evidence count has not yet reached the threshold at box 466, control circuit 80 can determine at box 468 that the OS rejection rule is not met. Control circuit 80 can then return to box 452 to wait for the next Vsense signal. In this example, when an alternating pattern is detected and the morphological matching criterion is met for a high-amplitude sensed event signal, the GMA result of VT / VF can be used to override the PWOS rejection rule by not counting or marking the Vsense signal as OS evidence. In this way, the current or most recent GMA result of VT / VF overrides the PWOS rejection rule by preventing the PWOS rejection rule from being met (OS evidence counter not incremented). In other examples, when an alternating pattern of a cardiac event signal is detected, the Vsense signal can be counted as OS evidence, but once the OS evidence count has reached the threshold, control circuit 80 can determine that the PWOS rejection rule is overridden based on the most recent GMA result being VT / VF. Therefore, it should be understood that the GMA result of VT / VF can override the PWOS rejection rule by preventing the rejection rule from being met (e.g., when an alternating pattern of a cardiac event signal is detected). Figure 11 (as shown in the example), or by having control circuit 80 ignore the rejection rule satisfied when the current GMA result is VT / VF (as described above). Figure 10 (As generally described) to cover the rejection rule. Regardless of the method, if NID is achieved and the most recent GMA result is VT / VF, control circuit 80 can detect VT / VF to enable ATP or electric shock delivery without suppressing or delaying detection due to the satisfaction of the PWOS rejection rule. PWOS may occur in the presence of a real VT / VF seizure, which can still be detected based on the achievement of GMA and NID. However, when PWOS is detected according to the satisfaction of the PWOS rejection rule and the most recent GMA result is not VT / VF, the PWOS rejection rule can cause control circuit 80 to suppress or delay VT / VF detection.

[0238] Other PWOS rejection rules, T-wave oversensing (TWOS) rejection rules, and / or non-cardiac noise oversensing rejection rules may be applied by control circuitry 80 to determine when oversensing may lead to erroneous NID when VT / VF is not present. Other examples of PWOS rejection rules that may be applied by control circuitry 80 (which may be covered by GMA results of VT / VF as disclosed herein) are generally disclosed in U.S. Patent Application Publication No. 2021 / 0170170 (Mischhler et al., filed June 10, 2021).

[0239] TWOS rejection rules that can be applied by control circuitry 80 (e.g., in...) Figure 10Examples (see box 408) are generally disclosed in U.S. Patent Nos. 9,597,525 (Cao et al., filed May 6, 2015) and 10,850,113 (Cao et al., filed July 20, 2017), both of which are incorporated herein by reference in their entirety. For example, the peak amplitude of a sensed event signal and the R-wave morphology match score of sensed event data identified as Vsense signals can be analyzed to determine when a TWOS rejection rule is satisfied. For example, TWOS evidence can be detected by control circuitry 80 when a specified number of recent Vsense signals include a threshold number of Vsense signal pairs that exhibit a high-low or low-high amplitude pattern and a corresponding high-low or low-high R-wave morphology match score pattern. When a threshold number of TWOS evidence thresholds are detected on the most recent 8, 10, 15, 20, 30, or other specified numbers of recent Vsense signals, control circuitry 80 can determine that a TWOS rejection rule is satisfied. In some examples, the TWOS rejection rule is overridden when the TWOS rejection rule is met and the current GMA result is VT / VF, allowing control circuitry 80 to detect VT / VF. In other examples, when TWOS evidence is detected based on amplitude and R-wave morphology matching scores of high-low or low-high modes, the current GMA result of VT / VF prevents the TWOS evidence counter from increasing, thus overriding the TWOS rejection rule.

[0240] It can be controlled by circuit 80, for example in Figure 10Examples of noise rejection rules applied at block 408 may include skeletal muscle noise rejection rules and / or electromagnetic interference (EMI) rejection rules. According to the techniques disclosed herein, noise rejection rules can be overridden by the GMA results of VT / VF. Examples of noise rejection rules that can be applied by control circuitry 80 are generally disclosed in U.S. Patent Nos. 10,470,681 (Greenhut et al., filed May 26, 2017) and 10,561,332 (Zhang et al., filed July 19, 2017), both of which are incorporated herein by reference in their entirety. The peak amplitude determined as sensed event data can be used to detect noise based on the maximum and minimum peak amplitudes for distinguishing noise pulses from ventricular event signals and / or for counting noise pulses. Normalized average rectified amplitude and / or maximum pulse width can be determined as sensed event data, which can be used by control circuitry 80 to distinguish noise pulses from real ventricular sensed event signals for determining when a noise rejection rule is met. Sensing event signals identified as noise signals based on sensing event data can cause the noise evidence counter to increase toward the threshold used to satisfy the noise rejection rule. The current GMA result of VT / VF can override the noise rejection rule by preventing the noise evidence counter from increasing (thus preventing the noise rejection rule from being satisfied) or by causing the control circuit 80 to ignore the noise rejection rule when it is satisfied.

[0241] Figure 12 This is a flowchart 500 of a method, executed by control circuitry 80, to determine when an SVT rejection rule is met, based on some examples. In this example, the criterion required to meet the SVT rejection rule may correspond to atrial fibrillation (AF) conducting to the ventricles. In this case, the rejection rule may be referred to as the AF rejection rule. However, other SVT rejection rules may be applied, and / or combined. Figure 12 The described SVT rejection rule criteria enable control circuitry 80 to suppress VT / VF detection when other types of SVT are occurring, including, but not limited to, AF conducted to the ventricles.

[0242] At block 502, control circuitry 80 receives Vsense signals from sensing circuitry 86. At block 504, control circuitry 80 can determine sensing event data corresponding to the Vsense signals. The sensing event data can be stored in memory 82 to enable control circuitry 80 to determine when a threshold number of sensing event data for Vsense signals satisfies the SVT rejection rule. As indicated above, sensing event data determined before and / or after transitioning to relevant state 2 can be used to determine the state of the rejection rule. Sensing event data buffered only from sensing channels 83 or 85 selected for VT / VF detection after transitioning to relevant state 2 can be analyzed by control circuitry 80 to determine whether the rejection rule is satisfied.

[0243] As described above, the sensing event data may include an RRI ending with the currently received Vsense signal. The sensing event data may include an R-wave morphology matching score, which is determined based on a segment of the sensing event signal buffered in memory 82, received from the morphology signal channel 87 in response to the Vsense signal.

[0244] At block 506, control circuitry 80 can update the RRI pattern based on sensed event data. The RRI pattern can be the most frequently occurring RRI among the most recent 12 to 30 RRI buffers, or a series of the most frequently occurring RRIs. In some examples, the RRI pattern can be the most common RRI determined from the most recent 24 RRIs. Control circuitry 80 can track the frequency of RRIs occurring within multiple RRI ranges in a histogram allocated in memory 82. For example, as an example, control circuitry 80 can record RRIs between 150 ms and 1 second, or between 150 ms and 600 ms, in the RRI histogram. In one example, the histogram can be divided into bin widths of 10 ms. In other examples, the histogram bins can have bin widths from 5 ms to 30 ms. An RRI pattern can be identified as a histogram bin with the maximum number of RRIs recorded for the corresponding RRI bin range. In some examples, at block 506, two of the most frequently occurring RRI ranges are determined by the histogram bin widths during the most recent 24 RRIs (or other specified number of RRIs). In other examples, three or more of the most frequent RRIs can be identified at box 506. For example, one, two or more of the most frequent RRIs can be identified as the RRI bin with the highest RRI count recorded in the corresponding bin among the most recent 16 to 30 RRIs. In other examples, an RRI pattern can be determined from all buffered RRIs, and at box 506, the range of most frequent RRIs can be determined as the RRI pattern. + 5ms, 10ms, 15ms, or other specified ranges from the RRI mode.

[0245] At box 508, control circuit 80 determines whether the RRI regularity criterion is met. When AF is conducted to the ventricles, the RRI is expected to be irregular. Control circuit 80 determines what percentage of all RRIs fall within one, two, or more RRI histogram bins (ranges) identified as the most frequently recorded bins at box 506. In other examples, control circuit 80 determines what percentage of all RRIs fall within a specified range of RRI patterns. Control circuit 80 determines whether the RRI is regular by comparing the percentage of RRIs recorded in the two most frequent RRI bins (each bin having a bin width of 10 ms) to a threshold percentage. If at least 80%, 90%, or 100% of the most recent 24 RRIs fall within the two most frequently recorded RRI bins, control circuit 80 determines at box 508 that the RRI regularity criterion is met. Control circuit 80 can then return to box 502 to await the next Vsense signal. The SVT rejection rule (in this case, the AF rejection rule) remains unmet, so that if the VTI / VFI counter reaches NID and other rejection rules are not met, VT / VF can be detected by the control circuit 80.

[0246] If a percentage of RRIs less than a threshold falls within the histogram bins of the two most frequently recorded RRIs (or other ranges of the most common RRIs identified at box 506), control circuit 80 determines that the RRIs are irregular. The RRI regularity criterion at box 508 is not met, which can be an indication of conduction AF. In one example, if less than 100% of the most recent 24 RRIs fall within the histogram bins of the two most frequently recorded RRIs, control circuit 80 determines at box 508 that the RRI regularity criterion is not met. During AF, depolarization from the atrium to the ventricle is expected to occur with irregular intervals. When the RRI regularity criterion is not met at box 508, the RRI irregularity criterion required to satisfy the SVT rejection rule can be met. Control circuit 80 can then proceed to box 510 to apply the R-wave morphology matching criterion.

[0247] Control circuit 80 can compare the R-wave morphology match score, buffered along with the sensed event data, with the SVT match threshold. The SVT match threshold can be defined differently from the match threshold applied to the R-wave morphology match score for other purposes, such as determining when the PWOS rejection rule is met, as described above. Figure 11As described. The SVT matching threshold can be relatively low, for example, less than the matching threshold used to identify the true R wave in an alternating high-low-high or low-high-low pattern of the sensed event signal. The SVT matching threshold can be 10% to 50% in various examples, and 10% to 30% in some examples. If at least a threshold percentage of the most recent morphological match scores meets the SVT matching threshold, the control circuit 80 can determine evidence of SVT. For example, when the RRI regularity criterion is not met (the “No” branch of box 508) and, as an example, at least 18 of the most recent morphological match scores are at least 10%, 15%, 20%, or 25%, the control circuit 80 can identify evidence of conducted AF. It should be understood that sensed event data for another specified number of recent Vsense event buffers can be analyzed, and / or thresholds different from the example thresholds provided herein can be used to determine when RRI irregularities and R wave morphological match scores meet the SVT rejection rule.

[0248] When the RRI regularity criterion is not met at the corresponding boxes 508 and 510, but the SVT morphology matching criterion is met, the control circuit 80 can determine whether the most recent GMA result is VT / VF. If so, the VT / VF classification of the cardiac signal segment can cover evidence of SVT. If the most recent GMA result is VT / VF, the control circuit 80 can cover the SVT rejection rule by determining that the SVT rejection rule is not met at box 514. In other examples, the control circuit 80 can determine that the SVT rejection rule is met based on the RRI regularity criterion not being met at box 508 and the R-wave morphology matching score of the threshold number at boxes 508 and 510 meeting the SVT matching threshold. However, the SVT rejection rule can be covered by a GMA result of VT / VF, such that if NID is reached, the SVT rejection rule is ignored or disregarded when the GMA result is VT / VF because the SVT rejection rule does not suppress VT / VF.

[0249] When the most recent GMA result is not VT / VF (e.g., when the GMA result is non-VT / VF or cardiac arrest) and the RRI regularity criterion is not met at block 508 but the SVT morphological matching criterion is met at block 510, the control circuit 80 may determine that the SVT rejection rule is met at block 516. If the VTI / VFI counter reaches NID through the selected sensing channel 83 or 85, the control circuit 80 may suppress VT / VF detection based on the satisfaction of the SVT rejection rule and the fact that it is not covered by GMA.

[0250] During relevant state 2, charging state 3, and / or re-detection state 5, additional SVT rejection rules may be applied. When a rejection rule is satisfied, each SVT rejection rule can be overridden by the GMA result of VT / VF. Each SVT rejection rule may be applied by control circuitry 80 by applying various criteria to sensed event data, such as RRI, R-wave morphology matching score, and / or signal characteristics derived from sensed event signal segments, to identify sensed event signals characterized by RRI and / or morphology that have a higher probability of occurring in the atrium and being conducted to the ventricles compared to the VT / VF signal waveform. Examples of sensed event data that can be determined from sensed event signal segments include the peak polarity pattern of the sensed event signal, the peak time interval from the maximum positive peak to the minimum negative peak of the sensed event signal, the normalized width of the sensed event signal, and the R-wave morphology matching score, to determine whether control circuitry 80 satisfies an SVT rejection rule. Other examples of SVT rejection rules applicable to suppressing VT / VF detection upon reaching NID are generally disclosed in U.S. Patent No. 10,555,684 (Zhang et al.), which is incorporated herein by reference in its entirety.

[0251] Figure 13 It is based on some examples that can be executed by control circuit 80 for use in Figure 5 The flowchart 550 illustrates a method for re-detecting VT / VF during operation in re-detection state 5 of a tachyarrhythmia treatment state. Control circuitry 80 transitions to re-detection state 5 at block 551. Control circuitry 80 can transition from treatment delivery state 4 to re-detection state 5 after delivering a CV / DF shock. In other examples, control circuitry 80 can transition to re-detection state 5 in response to meeting treatment discontinuation criteria after detecting VT / VF. Control circuitry 80 can determine when operating in charging state 3 ( Figure 5 (box 106) or when operating in treatment delivery state 4 ( Figure 5 (Box 108) meets the criteria for discontinuing treatment, such as during capacitor charging or when ATP or CV / DF shock delivery is synchronized with the patient’s heart rhythm until the time of delivery of ATP or CV / DF shock.

[0252] When control circuit 80 transitions to re-detection state 5 after treatment delivery, control circuit 80 may begin buffering new cardiac signal segments for use in performing GMA. When control circuit 80 transitions to re-detection state 5 in response to meeting treatment discontinuation criteria, the buffering or processing of cardiac signal segments for performing GMA may be in progress and does not necessarily restart after transitioning to re-detection state 5. GMA remains enabled, and the sensing channel 83 or 85 selected for reliable VT / VF detection, along with the programmed or increased sensitivity effective during initial VT / VF detection, remains active during re-detection state 5.

[0253] After delivering a CV / DF shock and transitioning to re-detection state 5, control circuit 80 may initiate a long pause confirmation interval (hereinafter referred to as the "pause confirmation interval") to detect post-shock cardiac arrest. If control circuit 80 transitions to re-detection state 5 in response to meeting the treatment discontinuation criteria, control circuit 80 may initiate a relatively long hysteresis pacing interval during which bradycardia sensing methods can be performed. The relatively long hysteresis pacing interval may be initiated to avoid bradycardia pacing pulses interfering with the re-detection of VT / VF after meeting the treatment discontinuation criteria. A relatively short pause confirmation interval may be initiated after a CV / DF shock to allow post-shock pacing to begin without excessive delay. The pause confirmation interval may be 2 to 4 seconds or 2.75 to 3.75 seconds, and in one example, it is 3.0 to 3.5 seconds. The relatively long hysteresis pacing interval (which may include a long pause detection interval followed by a pause confirmation interval) may be 4 to 9 seconds or 5 to 8 seconds, and in some examples 5.5 to 6.5 seconds or about 6 seconds. The bradycardia sensing and pacing control methods generally disclosed in U.S. Patent Application No. 17 / 822,681 (Greenhut et al., filed August 26, 2022), which is incorporated herein by reference in its entirety, and in U.S. Provisional Patent Application No. 63 / 486,725 (Greenhut et al., filed February 24, 2023), which is also incorporated herein by reference, may be combined with the techniques disclosed herein.

[0254] At block 552, control circuitry 80 may wait for a Vsense signal from the selected sensing channel 83 or 85. If no Vsense signal is received before the pause confirmation interval expires, as determined at block 554, control circuitry 80 may determine at block 556 whether the cardiac signal segment is classified as VT / VF based on GMA. After initiating the pause confirmation interval, buffering of the cardiac signal segment for GMA may begin, making the GMA result available after the pause confirmation interval expires. If the GMA result is VT / VF (the "Yes" branch of block 556), control circuitry 80 may restart the pause confirmation interval at block 568. If the GMA result is VT / VF, post-shock pacing is not delivered to avoid interference from pacing pulse delivery with the re-detection of VT / VF.

[0255] If the GMA result is not VT / VF, control circuitry 80 may control treatment delivery circuitry 84 at block 560 to deliver at least one pacing pulse. Control circuitry 80 may initiate a post-shock pacing period at block 560. This post-shock pacing period may be a specified duration, such as 10 seconds, 20 seconds, or 30 seconds. Post-shock pacing may be delivered by treatment delivery circuitry 84 at a programmed post-shock pacing rate during the post-shock pacing period. For example, the post-shock pacing rate may be 40, 50, or 60 pulses per minute. However, if a Vsense signal is received from sensing circuitry 86 (from selected sensing channel 83 or 85), the scheduled pacing pulse may be suppressed by treatment delivery circuitry 84. Control circuitry 80 may control treatment delivery circuitry 84 to deliver post-shock pacing in a VVI pacing mode, such that the Vsense signal suppresses the pacing pulse and restarts the pacing escape interval for scheduling the next pacing pulse. The therapeutic delivery circuit 84 can deliver VVI pacing during the post-shock pacing period or until the GMA result is VT / VF, which can terminate the post-shock pacing period.

[0256] Control circuitry 80 may proceed to block 562 (from blocks 554, 558, or 560) to determine whether termination criteria are met. It should be understood that control circuitry 80 may apply termination criteria to Vsense signals received from sensing circuitry 86 during a pause confirmation interval initiated after transitioning to re-detection state 5. Termination may be detected according to any of the examples given above. For example, control circuitry 80 may detect termination of VT / VF (after delivered or discontinued treatment) when at least eight Vsense signals are received at an RRI that meets a slow interval threshold (e.g., RCL plus 60 ms or another specified offset). Additionally or alternatively, control circuitry 80 may detect termination of VT / VF at block 562 when the median RRI determined from a specified number of recent RRIs (e.g., 6 to 12 RRIs) is longer than the duration of the VT / VF detection interval for a specified time interval (e.g., at least 10 to 20 seconds). For example, if the median RRI determined from the most recent 8 RRIs is consistently longer than the programmed VT detection interval by at least 20 seconds, the control circuit 80 may detect termination at block 562. In response to detecting VT / VF termination, the control circuit 80 may transition to an indifferent sensing state at block 564.

[0257] If the termination criteria are not met, control circuit 80 may wait for the next Vsense signal at block 552. If a post-shock pacing period has been initiated at block 560, the Vsense signal received at block 552 causes treatment delivery circuit 84 to suppress the scheduled ventricular pacing pulse. If no Vsense signal is received before the pacing interval expires, treatment delivery circuit 84 may deliver the scheduled pacing pulse. Although in Figure 13 While not explicitly stated, it should be understood that if the post-shock pacing period expires and the control circuit 80 is still operating in re-detection state 5, the control circuit 80 may restart the pause confirmation interval. However, if the post-shock pacing period is 10 seconds or longer, such as 30 seconds, it is likely that termination or re-detection of VT / VF can be detected before the post-shock pacing period expires.

[0258] In response to the Vsense signal received at block 552, control circuitry 80 determines sensing event data at block 570 for applying termination and re-detection criteria, including any rejection rules that may be enabled during re-detection state 5. Sensing event data may include the peak amplitude of the sensing event signal (which may be the maximum peak amplitude and / or maximum peak-to-peak amplitude of the rectified signal), RRI, and R-wave morphology matching score. Other sensing event data described herein may be determined at block 570 as needed for detection termination and for re-detection of VT / VF. At block 572, control circuitry 80 may determine whether RNID (Re-detection NID) has been reached. If not, control circuitry 80 may proceed to block 562 to determine whether the termination criteria have been met.

[0259] When the VTI / VFI counter of the selected sensing channel 83 or 85 meets the RNID (block 572), the control circuit 80 may apply one or more rejection rules at block 574 to distinguish between real VT / VF and oversensing of cardiac events, noise oversensing, and / or SVT that may lead to RNID based on the Vsense signal. The control circuit 80 may apply at least some of the rejection rules applied during the relevant state 2 for VT / VF detection. For example, the rules as described above may be applied during the re-detection state 5. Figure 11 The PWOS rejection rules are described. However, in some examples, at least some of the rejection rules applied during relevant state 2 may be disabled or not applied during re-inspection state 5. For example, SVT rejection rules may be disabled during re-inspection state 5, such as those combined with the above. Figure 12 The conducted AF rejection rule is described. Even during the singlet VT, the RRI after the delivered CV / DF shock may be irregular. The regularity criterion applied to the post-shock RRI to determine whether the conducted AF rejection rule is met may be unreliable for distinguishing between conducted AF and VT / VF after the delivery of a CV / DF shock. Therefore, during re-detection state 5, control circuit 80 may apply one or more rejection rules applied during the relevant sensing state 2, but may disable other rejection rules applied during the relevant sensing state 2.

[0260] As defined at block 574, when none of the applied rejection rules are satisfied, control circuit 80 may re-detect VT / VF at block 582 in response to satisfying RNID. Control circuit 80 may transition back to charging state 3 (e.g., ...). Figure 5 (As shown). When the rejection rule is met at block 574, the control circuit 80 can determine whether the GMA result is available. The rejection rule can be overridden by the GMA result of VT / VF. However, in some cases, RNID can be satisfied and the rejection rule can be satisfied before the GMA result is available.

[0261] Depending on the duration of the buffered cardiac signal segment and the required GMA processing time, the first GMA result may be unavailable for up to 3 to 4 seconds after transitioning to the re-detection state. Furthermore, buffering the cardiac signal segment for GMA can delay the post-shock artifact delay period, which can be 0.2 to 1 second, or about 0.5 seconds, following the delivered CV / DF shock. In some examples, such as the example where a 3-second cardiac signal segment is buffered for GMA, the buffering and processing time for determining the GMA result may therefore be unavailable for at least 3.5 seconds after transitioning to the re-detection state 5.

[0262] exist Figure 13 In the example shown, if the rejection rule is met at box 574 and can be overridden by GMA, but the GMA result is not yet available, control circuit 80 may suppress VT / VF re-detection at box 580 based on the satisfaction of the rejection rule. VT / VF re-detection may be suppressed at least until the GMA result is available. If the rejection rule is met at box 574 and the GMA result is available (the "Yes" branch of box 576), for example, determined in the last 0.5 to 1 second, control circuit 80 may proceed to box 578. When the GMA result is a VT / VF classification of the cardiac signal segment, control circuit 80 may re-detect VT / VF based on the GMA result satisfying both RNID and VT / VF (box 582). When the GMA result is available and is VT / VF, the rejection rule may be overridden. However, if the GMA result is available and is not VT / VF, for example, if the cardiac signal segment is classified as non-VT / VF or cardiac arrest, control circuit 80 may suppress VT / VF re-detection at box 580. The control circuit 80 can return to block 552 to wait for the next Vsense signal.

[0263] However, in other examples, when the rejection rule is met at block 574 and the GMA result is unavailable, but the RNID is reached via the VTI / VFI counter, the control circuit 80 may default to specifying the GMA result as VT / VF. When the RNID is met, the control circuit 80 may override the rejection rule satisfied by the default GMA result based on VT / VF. The control circuit 80 may proceed directly to block 582 to re-detect VT / VF and transition to charging state 3, instead of waiting for the GMA result to become available, even if the rejection rule is met. Based on the higher probability that VT / VF still exists when it was previously detected, VT / VF can be re-detected without waiting for the GMA result.

[0264] In some examples, multiple rejection rules may be applied during re-detection state 5. Any of the example rejection rules described herein may be applied at box 574. Each rejection rule may be applied to determine when a threshold number of Vsense signals (which contribute to achieving NID) is more likely to be an oversensitized signal or corresponds to depolarization conducted from the atrium rather than a true VT / VF R wave or fibrillation. In some examples, any or all of the applied rejection rules (e.g., TWOS rejection rule, PWOS rejection rule, one or more SVT rejection rules, and / or one or more noise rejection rules) may be overridden by the GMA result of VT / VF. The criteria used to apply rejection rules may be highly sensitive to the detection of oversensitization (P wave, T wave, or non-cardiac noise) or the detection of SVT, such that if a rejection rule is met, the GMA result may overridden a rejection rule that was incorrectly met. In this way, when PWOS, TWOS, SVT, or noise oversensing results in NID being met, PWOS, TWOS, SVT, or noise oversensing can be detected with high sensitivity according to the rejection rule criteria, but VT / VF detection is only suppressed if GMA results confirm that the cardiac signal segment is not classified as VT / VF.

[0265] However, it should be understood that in some cases, the rejection rules applied during re-detection state 5 may be rejection rules that cannot be overridden by the GMA result. Rejection rules can be considered effective in suppressing VT / VF re-detection before the GMA result is available and / or when the GMA result is available but not used to overridden the rejection rule. For example, at block 574, PWOS rejection rules, TWOS rejection rules, noise rejection rules, and / or other SVT rejection rules may be applied. If a rejection rule that cannot be overridden by the GMA result is satisfied, the control circuit 80 may suppress VT / VF re-detection until RNID is reached and all rejection rules are either not satisfied or overridden by the GMA result.

[0266] Figure 14The illustration 600 illustrates a method for performing GMA during a pacing period, based on some examples. As described above, control circuitry 80 may initiate a post-shock pacing period in response to the expiration of a pause confirmation interval without receiving a Vsense signal and a GMA result of non-VT / VF or cardiac arrest. To facilitate re-detection of VT / VF, control circuitry 80 may determine sensing event data of the Vsense signal received during (and after) the pacing period and may buffer and analyze cardiac signal segments according to the GMA for re-detection of VT / VF until termination or re-detection of VT / VF is detected, whichever occurs first. When post-shock pacing is not delivered, cardiac signal segments longer than one or more pacing escape intervals may be acquired without pacing artifacts that distort the cardiac signal segments. For example, a 3-second cardiac signal segment may be buffered independently of the timing of the Vsense signal for performing GMA. However, when pacing occurs after a shock delivery, multiple relatively short cardiac signal segments can be acquired over multiple pacing escape intervals to obtain the cumulative cardiac signal segment duration. The outcome of VT / VF, cardiac arrest, or non-VT / VF can be determined from this cumulative cardiac signal segment duration based on the GMA of the multiple shorter cardiac signal segments. Figure 14 The illustration shows a method for performing GMA by the control circuit 80 using a segment of cardiac signal buffered between pacing pulses (or bradycardia pacing pulses) after an electric shock.

[0267] In the example shown, the treatment delivery circuit 84 can deliver a CV / DF shock 604 in response to VT / VF detection. The control circuit 80 transitions to a re-detection state 5 and can initiate a pause confirmation interval 620 after a post-shock delay interval 605 (to allow signal artifacts to decay after the shock, subsequently enabling sensing of ventricular event signals and buffering of morphological signals from the morphological sensing channel 87). The post-shock delay interval 605 can be 0.2 seconds to 1 second long after the delivery of the CV / DF shock 604.

[0268] After initiating the pause confirmation interval 620, control circuitry 80 may enable buffering of cardiac signal segments from morphological signal 602 received from morphological sensing channel 87 during the pause confirmation interval 620. When the pause confirmation interval 620 expires without receiving a Vsense signal from sensing circuitry 86, control circuitry 80 may determine the result of a GMA performed on the cardiac signal segment buffered during the pause confirmation interval 620. If the GMA result is VT / VF, control circuitry 80 may restart the pause confirmation interval 620, and treatment delivery circuitry 84 may not deliver a pacing pulse. However, in the example shown, the GMA result is not the VT / VF classification of the cardiac signal segment as indicated at 621 (e.g., the GMA result could be a non-VT / VF or cardiac arrest classification). Treatment delivery circuitry 84 may deliver ventricular pacing pulse 622. Control circuitry 80 may, for example, initiate pacing period 640 and initiate pacing escape interval 612 to schedule the next pacing pulse 634 according to a programmed post-shock pacing rate.

[0269] Buffering of cardiac signal segments for GMA can remain enabled during pacing phase 640. However, to avoid very slow pacing rates or long delays between pacing pulses used to buffer relatively long cardiac signal segments for GMA, control circuitry 80 can buffer morphological signal 602 during multiple relatively short time intervals 630a-630e during pacing escape interval 612.

[0270] Control circuitry 80 may wait for a pacing artifact delay interval 635 after the first pacing pulse 622 and each subsequent pacing pulse 634, and then initiate a cardiac signal fragment buffering during relatively short time intervals 630a-630e. If no Vsense signal is received during the pacing escape interval 612, treatment delivery circuitry 84 may deliver the pacing pulse 634 after the pacing escape interval 612 has elapsed. Control circuitry 80 may restart the pacing escape interval 612, wait for the pacing artifact delay interval 635, and buffer the cardiac signal fragments sensed during the relatively short time intervals indicated by each time interval in the transit intervals 630a-630e. In various examples, the pacing artifact delay interval 635 may be 200 ms to 500 ms and may be the same as or relatively shorter than the post-shock delay interval 605.

[0271] However, a relatively short cardiac signal segment corresponding to one of the time intervals 630a-630e may not be sufficient to determine VT / VF, non-VT / VF, or cardiac arrest outcomes with high confidence based on GMA. Therefore, control circuit 80 may determine VT / VF morphological measures within multiple relatively short time intervals 630a-630e to determine GMA outcomes based on the cumulative duration of multiple post-pacing cardiac signal segments. The VT / VF morphological measures determined from each cardiac signal segment buffered within time intervals 630a-630e may include SW and MP, and in some examples include amplitude measures, rate measures, LSC, and / or noise measures, for example, as combined above. Figure 9 The VT / VF morphological measure determined for each individual post-pacing cardiac signal segment corresponding to time intervals 630a-630e can be buffered in memory 82 as overall morphological data. In some examples, control circuitry 80 can determine whether a relatively short cardiac signal segment is classified as VT / VF, cardiac arrest, or non-VT / VF based on the determined measure and a modified threshold used to classify the relatively short cardiac signal segment. Control circuitry 80 can accordingly label the cardiac signal segments in memory 82.

[0272] However, the control circuit 80 may delay, suppress, or terminate the pacing period 640 or cover the VT / VF rejection rule without based on the GMA classification of a relatively short cardiac signal segment corresponding to one of the time segments 630a-630e. After the pacing escape interval 612 has elapsed (when no Vsense signal was received during the pacing escape interval), the treatment delivery circuit 84 may deliver a pending pacing pulse 634 until a specified number of short cardiac signal segments are acquired and analyzed according to the GMA. The control circuit 80 may be configured to accumulate overall morphological data from multiple post-pacing cardiac signal segments sensed within time intervals 630a-630e during consecutive pacing escape intervals 612, each initiated in response to a delivered pacing pulse (VP) 632 or 634. When a threshold number of post-paced cardiac signal segments (corresponding to time segments 630a-630e, collectively referred to as 630) are individually classified as VT / VF evidence segments, the control circuit 80 can determine the GMA result of the accumulated post-paced cardiac signal segments buffered within the time interval 630a-630e as VT / VF.

[0273] Compared to the VT / VF criteria, which can be applied to relatively long cardiac signal segments (e.g., a 3-second segment buffered during a 620-second pause confirmation interval), a modified VT / VF criteria can be used to classify individual post-paced cardiac signal segments as VT / VF. For example, as combined with Figure 9As described, when the time interval 630a-630e is 0.5 seconds, when MP is at least 60 and the SW / MP ratio is greater than -1 and less than or equal to 0.085, the control circuit 80 can classify the corresponding relatively short cardiac signal segments as VT / VF. In one example, when at least 3, 4, 5, 6, or other specified number of relatively short cardiac signal segments are classified as VT / VF, for example, according to a modified VT / VF criterion, the GMA result can be determined by the control circuit 80 as VT / VF. During the pacing period 640, the threshold number of short cardiac signal segments classified as VT / VF may or may not need to be continuous.

[0274] In the illustrative example shown, control circuitry 80 may classify short cardiac signal segments corresponding to time interval 630e as VT / VF. When the VT / VF classification is the 5th VT / VF classification (e.g., all cardiac signal segments corresponding to time intervals 630a-e are classified as VT / VF), control circuitry 80 determines the GMA result as VT / VF, as indicated at time 636. Control circuitry 80 may cancel pending pacing pulses scheduled at the expiration of the currently running pacing escape interval 612 in response to the GMA result of the VT / VF classification for a threshold number of short cardiac signal segments. Control circuitry 80 may terminate pacing period 640 in response to the GMA result of the VT / VF.

[0275] Control circuit 80 can restart the pause confirmation interval 620'. In this way, GMA results can be obtained based on the classification of multiple discontinuous cardiac signal segments during pacing after shock, for use in terminating the pacing period and for re-detecting VT / VF. Multiple discontinuous cardiac signal segments can be two or more segments and may or may not have the same duration. However, when combined, multiple discontinuous cardiac signal segments have a cumulative duration, which can provide GMA results for VT / VF, non-VT / VF, or cardiac arrest based on the classification of individual cardiac signal segments. It should be understood that the threshold number of short cardiac signal segments used to determine the GMA result for VT / VF can be a percentage of short cardiac signal segments (e.g., X out of Y). Short cardiac signal segments classified as VT / VF may not necessarily need to be continuous, such as... Figure 14 As shown. GMA results can be obtained when the required number of short signal segments with the minimum cumulative cardiac signal segment duration have been analyzed. For example, at least Y short cardiac signal segments or a total minimum cumulative duration of 2 seconds, 2.5 seconds, 3 seconds, or 3.5 seconds, or other specified cumulative durations of multiple cardiac signal segments can be analyzed to obtain GMA results.

[0276] When fewer than a threshold number of short cardiac signal segments are classified as VT / VF (e.g., fewer than X out of Y), the GMA result can be either non-VT / VF or cardiac arrest. More generally, when fewer than a specified percentage of the cumulative duration of multiple cardiac signal segments are classified as VT / VF, the GMA result is not VT / VF (e.g., cardiac arrest or non-VT / VF). If the cardiac arrest criterion is met for the threshold number of short cardiac signal segments or the percentage of the cumulative duration of multiple cardiac signal segments, the GMA result can be cardiac arrest. In response to a non-VT / VF or cardiac arrest GMA result, pacing phase 640 may continue operating. Pacing phase 640 may continue operating as long as fewer than a threshold number of short cardiac signal segments (or fewer than a percentage of the cumulative duration of cardiac signal segments) are classified as VT / VF (and no tachyarrhythmic operational state transition occurs).

[0277] In various examples, the GMA result for terminating VT / VF during pacing period 640 may require classifying at least a minimum number of short cardiac signal fragments (e.g., 2, 3, 4, 5, 6, 7, or 8 cardiac signal fragments) buffered during the pacing escape interval as VT / VF before terminating pacing period 640. For example, assuming no Vsense signal is received, at least 3, 4, 5, 6, 8, or other selected number of pacing pulses may be delivered before pacing period 640 is terminated by control circuitry 80 based on the GMA of relatively short cardiac signal fragments sensed between delivered pacing pulses. Control circuitry 80 may determine the GMA result as VT / VF classification when a predetermined percentage or ratio, such as at least half, at least two-thirds, at least three-quarters, 100%, or other selected percentage or portion of a specified minimum number of cardiac signal fragments buffered during pacing escape interval 612 is classified as VT / VF fragments. In some examples, in addition to classifying short cardiac signal fragments of a threshold number as VT / VF, it may be necessary to classify the most recent one, two, or three cardiac signal fragments as VT / VF in order to terminate the pacing period 640 based on GMA results.

[0278] The GMA result based on multiple relatively short cardiac signal segments obtained during pacing after the shock can be used to override a rejection rule that has already been met. When the GMA is not VT / VF, the met rejection rule allows control circuit 80 to suppress VT / VF re-detection if RNID is reached. However, if the GMA result based on multiple post-pacing cardiac signal segments is VT / VF, the rejection rule can be overridden, allowing control circuit 80 to re-detect VT / VF if RNID is reached.

[0279] In other examples, a post-pacing cardiac signal segment acquired over multiple pacing intervals can be obtained for up to a specified number of pacing pulses. After a specified number of pacing pulses (e.g., 3 to 15 pacing pulses), control circuitry 80 can control treatment delivery circuitry 84 to suppress the next pacing pulse for at least three seconds (or other specified time interval) to allow buffering of a full-length cardiac signal segment, such as a 3-second cardiac signal segment, that would normally be used to perform a GMA when pacing is not delivered. If the GMA is not VT / VF, control circuitry 80 can enable treatment delivery circuitry 84 to deliver pacing pulses and resume delivery of ventricular pacing pulses at a post-shock pacing rate for another specified number of pacing pulses or until pacing period 640 expires. Control circuitry 80 can resume buffering of the post-pacing cardiac signal segment during delivery of another specified number of pacing pulses.

[0280] In other examples, relatively short post-pacing cardiac signal segments can be classified according to GMA (with modified thresholds applied to the morphological measure as needed). When determining the number (which can be one or more) thresholds for VT / VF classification of relatively short post-pacing cardiac signal segments (obtained during the pacing escape interval), control circuitry 80 can control treatment delivery circuitry 84 to suppress the next scheduled pacing pulse. Control circuitry 80 can initiate a pause confirmation interval to allow the acquisition of a full-length continuous cardiac signal segment, such as a 3-second cardiac signal segment, for obtaining a GMA result based on a relatively long continuous cardiac signal segment. This GMA result can be used to terminate the pacing period 640 and / or re-detect VT / VF. In this way, the GMA classification of relatively short, discontinuous post-pacing cardiac signal segments obtained during the pacing escape interval can be used to trigger a buffer of relatively long, continuous cardiac signal segments during pacing suppression. Relatively long, continuous cardiac signal segments can be analyzed to obtain GMA results for overriding rejection rules and / or terminating the post-shock pacing period.

[0281] exist Figure 14In the example, no Vsense signal was received during the pacing period 640 after the shock. It should be recognized that in some cases, a Vsense signal may be received during the pacing escape interval. In this case, the pacing escape interval may be restarted, and the post-pacing cardiac signal segment may be discarded (if initiated). The next post-pacing cardiac signal segment may be buffered after the delivery of the subsequent pacing pulse. However, in other examples, if a Vsense signal is received before the pacing escape interval expires, buffering of the post-pacing cardiac signal segment may continue when the pacing escape interval is restarted. Buffering of the post-pacing cardiac signal may continue until the pacing escape interval expires or until the cardiac signal segment has been buffered for a normal duration (e.g., 3 seconds), whichever comes first. For example, if a complete 3-second cardiac signal segment is buffered before the delivery of the next pacing pulse, the GMA outcome can be determined according to the classification criteria applied to cardiac signal segments of normal duration.

[0282] If a cardiac signal segment shorter than 3 seconds is buffered, the segment can be discarded. Alternatively, if a cardiac signal segment shorter than 3 seconds is buffered, the segment can be divided into multiple short cardiac signal segments, for example, equal to the post-pacing time interval 630a-630e (where any excess portion of the segment is discarded). For example, if a 2.25-second cardiac signal segment is buffered due to pacing inhibition caused by the Vsense signal, followed by a subsequent pacing pulse, four 0.5-second segments can be analyzed, and the remaining 0.25 seconds can be discarded. Each short cardiac signal segment can be classified according to GMA to obtain GMA results after at least Y short cardiac signal segments or a minimum cumulative duration of multiple cardiac signal segments have been classified. Therefore, two additional cardiac signal segments with different durations can be combined to obtain the cumulative duration of the cardiac signal segments from which GMA results can be obtained.

[0283] This document also discloses the subject matter of the following embodiments:

[0284] Example 1. A medical device comprising a sensing circuit configured to sense a plurality of cardiac signals and to sense ventricular event signals from the plurality of cardiac signals. The medical device further comprises a control circuit communicating with the sensing circuit. The control circuit is configured to, for each of the plurality of ventricular event signals sensed by the sensing circuit, determine sensed event data from the plurality of cardiac signals and obtain a first cardiac signal segment from the plurality of cardiac signals sensed by the sensing circuit. The first cardiac signal segment may have a first duration and an activation time independent of the timing of the ventricular event signals sensed by the sensing circuit. The control circuit may also be configured to perform morphological analysis of the first cardiac signal segment for classifying the first cardiac signal segment into one of ventricular tachyarrhythmias, non-ventricular tachyarrhythmias, or cardiac arrest. The control circuitry may also be configured to: determine from the ventricular event signal sensed by the sensing circuitry that a first desired number of tachyarrhythmia intervals for detecting ventricular tachyarrhythmias have been reached; determine, based on the sensed event data, that a rejection rule for suppressing tachyarrhythmia detection is satisfied; and determine, based on the morphological analysis, that the first cardiac signal segment is classified as a ventricular tachyarrhythmia. The control circuitry may also be configured to override the rejection rule for suppressing tachyarrhythmia detection by: detecting a ventricular tachyarrhythmia in response to reaching the first desired number of tachyarrhythmia intervals and the first cardiac signal segment being classified as a ventricular tachyarrhythmia based on the morphological analysis. The medical device may also include a treatment delivery circuitry including a capacitor. The treatment delivery circuitry may be configured to initiate charging of the capacitor for treatment delivery in response to the control circuitry detecting the ventricular tachyarrhythmia.

[0285] Example 2. According to the medical device of Example 1, wherein the treatment delivery circuit is configured to deliver the treatment by delivering either antitachycardia pacing or CV / DF electrical stimulation in response to the control circuit detecting the ventricular tachyarrhythmia. The control circuit may also be configured to, after delivering the treatment, obtain a post-treatment cardiac signal segment from one of the plurality of cardiac signals sensed by the sensing circuit, and determine from the sensed ventricular event signal a second desired number of tachyarrhythmia intervals for re-detecting the ventricular tachyarrhythmia after delivering the treatment. The second desired number of tachyarrhythmia intervals may be less than the first desired number of tachyarrhythmia intervals. The control circuit may also be configured to determine, based on analysis of the plurality of cardiac signals sensed by the sensing circuit, a rejection rule for suppressing the detection of the ventricular tachyarrhythmia is satisfied; to determine, based on the morphological analysis, that the post-treatment cardiac signal fragment is not classified as a ventricular tachyarrhythmia; and, in response to the post-treatment cardiac signal fragment not being classified as a ventricular tachyarrhythmia, to suppress re-detection of the ventricular tachyarrhythmia in response to reaching the second desired number of tachyarrhythmia intervals and satisfying the rejection rule.

[0286] Example 3. According to the medical device of Example 1, wherein the treatment delivery circuit is configured to deliver the treatment by delivering either antitachycardia pacing or CV / DF electrical stimulation in response to the control circuit detecting the ventricular tachyarrhythmia. The control circuit is further configured to, after delivering the treatment, obtain a post-treatment cardiac signal segment from one of the plurality of cardiac signals sensed by the sensing circuit; and determine from the sensed ventricular event signal a second desired number of tachyarrhythmia intervals for re-detecting the ventricular tachyarrhythmia after delivering the treatment. The second desired number of tachyarrhythmia intervals may be less than the first desired number of tachyarrhythmia intervals. The control circuit may also be configured to: determine, based on analysis of the plurality of cardiac signals, a rejection rule satisfying the requirement to suppress the detection of the tachyarrhythmia; determine, based on the morphological analysis, that the post-treatment cardiac signal segment is classified as a ventricular tachyarrhythmia; and, in response to the classification of the post-treatment cardiac signal segment as a ventricular tachyarrhythmia, override the rejection rule for suppressing the detection of the tachyarrhythmia. The control circuit may be configured to re-detect the ventricular tachyarrhythmia in response to reaching the second desired number of tachyarrhythmia intervals and the rejection rule being overridden.

[0287] Example 4. A medical device according to any one of Examples 1 to 3, wherein determining a rejection rule for suppressing the detection of the ventricular tachyarrhythmia may include: for each of the plurality of sensed ventricular event signals, obtaining a sensed event signal segment from the plurality of cardiac signals, and determining at least a portion of the sensed event data from the sensed event signal segment. The sensed event signal segment may have an activation time that depends on the timing of the sensed ventricular event signal.

[0288] Example 5. The medical device according to any one of Examples 1 to 4, wherein the control circuit is further configured to determine the sensing event data by determining at least one or more of the following: the peak amplitude of the sensing event, the RR interval at which the sensing event signal ends, and / or the R-wave morphology matching fraction.

[0289] Example 6. The medical device according to Example 5, wherein the control circuit is further configured to determine that a rejection rule for suppressing the detection of the ventricular tachyarrhythmia is satisfied by: increasing the cardiac event oversensing count in response to: detecting an alternating pattern of high and low sensing event peak amplitudes in the sensing event data; and determining that the R-wave morphology matching score of the sensing event data corresponding to at least one of the high sensing event peak amplitudes in the sensing event data satisfies a matching threshold. The control circuit may also be configured to determine that the cardiac event oversensing count reaches an oversensing threshold, and to determine that the rejection rule is satisfied in response to determining that the cardiac event oversensing count reaches the oversensing threshold.

[0290] Example 7. According to the medical device of Example 5, the control circuitry may further be configured to determine whether a rejection rule for suppressing the detection of the ventricular tachyarrhythmia is satisfied by: determining the most common RR interval range from the determined RR intervals; determining that a percentage of the determined RR intervals match the most common RR interval range; and determining that at least a threshold number of the R-wave morphology matching scores are greater than a supraventricular tachyarrhythmia matching threshold. The control circuitry may further be configured to determine whether the rejection rule is satisfied in response to determining that a percentage of the determined RR intervals match the most common RR interval range and determining that at least a threshold number of the R-wave morphology matching scores are greater than the supraventricular tachyarrhythmia matching threshold.

[0291] Example 8. The medical device according to Example 7, wherein the control circuit is further configured to disable the rejection rule in response to the treatment delivery circuit delivering the treatment.

[0292] Example 9. The medical device according to Example 1, wherein the treatment delivery circuit is configured to deliver the treatment by delivering either anti-tachyarrhythmic pacing or CV / DF electrical stimulation in response to the control circuit detecting the ventricular tachyarrhythmia. The control circuit is further configured to initiate a pause confirmation interval after the treatment is delivered, determine that no ventricular event signal is sensed by the sensing circuit during the pause confirmation interval, and acquire a post-treatment cardiac signal fragment during the pause confirmation interval. The control circuit is further configured to determine, based on the morphological analysis, that the post-treatment cardiac signal fragment is classified as either cardiac arrest or a non-ventricular tachyarrhythmia, and to initiate a pacing period in response to the post-treatment cardiac signal fragment being classified as either cardiac arrest or a non-ventricular tachyarrhythmia based on the morphological analysis.

[0293] Example 10. The medical device according to Example 9, wherein the treatment delivery circuit is further configured to deliver cardiac pacing pulses in response to the control circuit initiating the pacing period. The control circuit may also be configured to acquire at least one post-pacing cardiac signal segment and, based on the morphological analysis, determine that at least a threshold portion of the cumulative duration of a plurality of cardiac signal segments including the at least one post-pacing cardiac signal segment is classified as a ventricular tachyarrhythmia. The control circuit may also be configured to re-detect the ventricular tachyarrhythmia in response to the classification of at least the threshold portion of the cumulative duration of the plurality of cardiac signal segments as a ventricular tachyarrhythmia. The control circuit may also be configured to terminate the pacing period in response to the re-detection of the ventricular tachyarrhythmia.

[0294] Example 11. The medical device according to Example 10, wherein the control circuitry is further configured to schedule each of a plurality of cardiac pacing pulses delivered by the treatment delivery circuitry during the pacing period by initiating a pacing escape interval. The control circuitry is further configured to obtain the cumulative duration of the plurality of cardiac signal segments by obtaining each of a plurality of post-pacing cardiac signal segments during a corresponding pacing escape interval within the pacing escape interval.

[0295] Example 12. The medical device according to Example 9, wherein the treatment delivery circuit is further configured to deliver cardiac pacing pulses in response to the control circuit initiating the pacing period. The control circuit is further configured to acquire one or more post-pacing cardiac signal segments, wherein each post-pacing cardiac signal segment may be shorter than the first duration of the first cardiac signal segment. The control circuit is further configured to determine, based on the morphological analysis, that at least a threshold portion of the one or more post-pacing cardiac signal segments is classified as a ventricular tachyarrhythmia. The control circuit is further configured to control the treatment delivery circuit to suppress cardiac pacing delivery in response to at least the threshold portion of the one or more post-pacing cardiac signal segments being classified as a ventricular tachyarrhythmia. The control circuit may acquire a second cardiac signal segment when the cardiac pacing is suppressed. The second cardiac signal segment may have a second duration equal to the first duration of the first cardiac signal segment. The control circuit is further configured to determine, based on the morphological analysis, whether the second cardiac signal segment is classified as a ventricular tachyarrhythmia. The control circuitry can be configured to terminate the pacing period when the second cardiac signal segment is classified as a ventricular tachyarrhythmia based on the morphological analysis. The control circuitry can also be configured to control the therapeutic delivery circuitry to resume delivery of cardiac pacing pulses in response to the second cardiac signal segment not being classified as a ventricular tachyarrhythmia based on the morphological analysis.

[0296] Example 13. A medical device according to any one of Examples 1 to 12, wherein the control circuit is further configured to perform the morphological analysis of the first cardiac signal segment by: determining an amplitude amount based on the first cardiac signal segment; performing cardiac arrest analysis to classify the first cardiac signal segment as cardiac arrest or a non-ventricular tachyarrhythmia when the amplitude amount is less than an amplitude threshold; and performing tachyarrhythmia analysis to classify the first cardiac signal segment as a ventricular tachyarrhythmia or a non-ventricular tachyarrhythmia when the amplitude amount is at least the threshold amplitude.

[0297] Example 14. The medical device according to Example 13, wherein the control circuit is further configured to perform the rapid arrhythmia analysis of the first cardiac signal segment by determining at least one of the following: the average time period from the first cardiac signal segment and / or the spectral width from the first cardiac signal segment.

[0298] Example 15. A medical device according to any one of Examples 1 to 14, wherein the control circuitry is further configured to: obtain a previous cardiac signal segment from the plurality of cardiac signal segments before obtaining the first cardiac signal segment; and determine, based on the morphological analysis performed on the previous cardiac signal segment, that the previous cardiac signal segment is classified as one of a non-ventricular tachyarrhythmia or cardiac arrest. The control circuitry may be configured to suppress the detection of ventricular tachyarrhythmias in response to reaching the first desired number of tachyarrhythmia intervals, the previous cardiac signal segment being classified as one of a non-ventricular tachyarrhythmia or cardiac arrest, and satisfying the rejection rule.

[0299] Example 16. The medical device according to Example 1, wherein the control circuitry is further configured to determine, based on analysis of the plurality of cardiac signals sensed by the sensing circuitry after initiation of charging of the capacitor, that treatment termination criteria are met. The treatment delivery circuitry may also be configured to terminate the delivery of treatment in response to the control circuitry determining that the treatment termination criteria are met. The control circuitry may also be configured to determine from the ventricular sensing event signal a number of tachyarrhythmia intervals that reach a threshold for re-detecting the ventricular tachyarrhythmia after termination of treatment delivery. The control circuitry may also be configured to re-detect the ventricular tachyarrhythmia in response to reaching the threshold number of tachyarrhythmia intervals and one of the following: a) determining that the rejection rule for suppressing tachyarrhythmia detection is met; or b) determining that the rejection rule for suppressing tachyarrhythmia detection is met, and a second cardiac signal fragment obtained from the plurality of cardiac signals is classified as a ventricular tachyarrhythmia based on the morphological analysis.

[0300] Example 17. A method comprising: sensing a plurality of cardiac signals; sensing ventricular event signals from the plurality of cardiac signals; and for each of the plurality of sensed ventricular event signals, determining sensed event data from the plurality of cardiac signals. The method may further comprise obtaining a first cardiac signal segment from the plurality of cardiac signals. The first cardiac signal segment may have a first duration and an activation time independent of the timing of the ventricular event signals sensed by the sensing circuit. The method may further comprise performing morphological analysis of the first cardiac signal segment to classify the first cardiac signal segment as one of ventricular tachyarrhythmia, non-ventricular tachyarrhythmia, or cardiac arrest. The method may further comprise: determining from the ventricular event signals a first desired number of tachyarrhythmia intervals for detecting vent...

Claims

1. A medical device, the medical device comprising: The sensing circuit is configured to: Detect multiple cardiac signals; as well as ventricular event signals are sensed from the plurality of cardiac signals; A control circuit, which communicates with the sensing circuit, is configured to: For each of the plurality of ventricular event signals sensed by the sensing circuit, sensed event data is determined from the plurality of cardiac signals; A first cardiac signal segment is obtained from the plurality of cardiac signals sensed by the sensing circuit, the first cardiac signal segment having a first duration and an activation time independent of the timing of the ventricular event signals sensed by the sensing circuit; Perform morphological analysis on the first cardiac signal segment to classify the first cardiac signal segment into one of ventricular tachyarrhythmia, non-ventricular tachyarrhythmia, or cardiac arrest. The ventricular event signal sensed by the sensing circuit is used to determine a first required number of tachyarrhythmia intervals for detecting ventricular tachyarrhythmias. Based on the sensed event data, a rejection rule is determined that satisfies the requirement to suppress the detection of rapid arrhythmias; Based on the morphological analysis, the first cardiac signal segment was classified as a ventricular tachyarrhythmia; as well as The rejection rule for suppressing the detection of tachyarrhythmias is overridden by the following operation: in response to reaching the first required number of tachyarrhythmia intervals and the first cardiac signal segment being classified as a ventricular tachyarrhythmia based on the morphological analysis, a ventricular tachyarrhythmia is detected. as well as A treatment delivery circuit, comprising a capacitor, configured to initiate charging of the capacitor in response to the control circuit detecting the ventricular tachyarrhythmia for delivering treatment.

2. The medical device according to claim 1, wherein: The treatment delivery circuit is configured to deliver the treatment by delivering either antitachycardia pacing or CV / DF electric shock in response to the control circuit detecting the ventricular tachyarrhythmia; and The control circuit is also configured to: After the treatment is delivered, a post-treatment cardiac signal fragment is obtained from one of the plurality of cardiac signals sensed by the sensing circuit; The sensed ventricular event signal determines a second required number of tachyarrhythmia intervals for re-detection of the ventricular tachyarrhythmia after delivery of the treatment, the second required number of tachyarrhythmia intervals being less than the first required number of tachyarrhythmia intervals; Based on the analysis of the plurality of cardiac signals sensed by the sensing circuit, a rejection rule is determined that is satisfied to suppress the detection of the ventricular tachyarrhythmia. Based on the morphological analysis, it was determined that the cardiac signal fragment after treatment was not classified as ventricular tachyarrhythmia; as well as In response to the fact that the post-treatment cardiac signal fragment is not classified as a ventricular tachyarrhythmia, and in response to reaching the second required number of tachyarrhythmia intervals and satisfying the rejection rule, re-detection of the ventricular tachyarrhythmia is suppressed.

3. The medical device according to claim 1, wherein: The treatment delivery circuit is configured to deliver the treatment by delivering either antitachycardia pacing or CV / DF electric shock in response to the control circuit detecting the ventricular tachyarrhythmia. The control circuit is further configured to: After the treatment is delivered, a post-treatment cardiac signal fragment is obtained from one of the plurality of cardiac signals sensed by the sensing circuit; The sensed ventricular event signal determines a second required number of tachyarrhythmia intervals for re-detection of the ventricular tachyarrhythmia after delivery of the treatment, the second required number of tachyarrhythmia intervals being less than the first required number of tachyarrhythmia intervals; Based on the analysis of the plurality of cardiac signals, a rejection rule is determined to suppress the detection of the tachyarrhythmia. Based on the morphological analysis, the post-treatment cardiac signal fragment was classified as ventricular tachyarrhythmia. In response to the classification of the post-treatment cardiac signal fragment as ventricular tachyarrhythmia, the rejection rule used to suppress the detection of the tachyarrhythmia is overridden; and In response to reaching the second required number of tachyarrhythmic intervals and the rejection rule being overridden, the ventricular tachyarrhythmia is re-detected.

4. The medical device according to any one of claims 1 to 3, wherein determining whether a rejection rule for suppressing the detection of said ventricular tachyarrhythmia is satisfied includes: For each of the plurality of sensed ventricular event signals: Obtain sensing event signal segments from the plurality of cardiac signals, the sensing event signal segments having a start time that depends on the timing of the sensed ventricular event signal; as well as At least a portion of the sensing event data is determined from the sensing event signal segment.

5. The medical device according to any one of claims 1 to 4, wherein the control circuitry is further configured to determine the sensing event data by determining the following: Sensing event peak amplitude; The RR interval ending with the sensed event signal; and R-wave morphology matching score.

6. The medical device of claim 5, wherein the control circuitry is further configured to determine, by means of the following operations, a rejection rule for suppressing the detection of the ventricular tachyarrhythmia is satisfied: The following measures are taken to increase the count of excessive cardiac events: An alternating pattern of high and low peak amplitude of sensing events was detected in the sensing event data; as well as Determine that the R-wave morphology matching score of the sensing event data corresponding to at least one of the high sensing event peak amplitudes of the sensing event data satisfies a matching threshold; Determine that the cardiac event oversensing count has reached the oversensing threshold; as well as In response to determining that the cardiac event oversensing count has reached the oversensing threshold, the rejection rule is satisfied.

7. The medical device of claim 5, wherein the control circuitry is further configured to determine, by means of the following operation, a rejection rule for suppressing the detection of the ventricular tachyarrhythmia: Determine the most common range of RR intervals from the determined RR intervals; The determined RR intervals that are less than a threshold percentage are matched with the most common RR interval range; Determine that at least a threshold number of the R-wave morphology matching scores are greater than the supraventricular tachyarrhythmia matching threshold; as well as The rejection rule is determined in response to determining that a percentage of determined RR intervals less than the threshold percentage match the most common RR interval range and that at least a number of the R-wave morphology matching scores are greater than the supraventricular tachyarrhythmia matching threshold.

8. The medical device of claim 7, wherein the control circuitry is further configured to disable the rejection rule in response to the treatment delivery circuitry delivering the treatment.

9. The medical device according to claim 1, wherein: The treatment delivery circuit is configured to deliver the treatment by delivering either anti-tachyarrhythmic pacing or CV / DF electrical stimulation in response to the control circuit detecting the ventricular tachyarrhythmia; and The control circuit is further configured to: A pause confirmation period is initiated after the delivery of the treatment; It was determined that no ventricular event signal was detected by the sensing circuit during the pause confirmation interval; Post-treatment cardiac signal fragments were obtained during the pause confirmation period; Based on the morphological analysis, the post-treatment cardiac signal fragments were classified as either cardiac arrest or non-ventricular tachyarrhythmia. as well as The pacing phase is initiated in response to a cardiac signal fragment after treatment that is classified as cardiac arrest or non-ventricular tachyarrhythmia based on the morphological analysis.

10. The medical device according to claim 9, wherein: The treatment delivery circuit is also configured to deliver cardiac pacing pulses in response to the control circuit initiating the pacing period; and The control circuit is further configured to: Obtain at least one post-pacing cardiac signal fragment; Based on the morphological analysis, at least a threshold portion of the cumulative duration of multiple cardiac signal segments, including at least one post-pacing cardiac signal segment, is classified as a ventricular tachyarrhythmia. The ventricular tachyarrhythmia is re-detected in response to at least a threshold portion of the cumulative duration of the plurality of cardiac signal segments being classified as a ventricular tachyarrhythmia; as well as The pacing period is terminated in response to the re-detection of the ventricular tachyarrhythmia.

11. The medical device according to claim 9, wherein: The therapeutic delivery circuit is also configured to deliver cardiac pacing pulses in response to the control circuit initiating the pacing period. The control circuit is further configured to: One or more post-paced cardiac signal segments are obtained, each post-paced cardiac signal segment being shorter than the first duration of the first cardiac signal segment; Based on the morphological analysis, at least a threshold portion of one or more post-pacing cardiac signal segments is classified as a ventricular tachyarrhythmia. The therapeutic delivery circuit is controlled to suppress cardiac pacing delivery in response to at least the threshold portion of one or more post-pacing cardiac signal segments being classified as ventricular tachyarrhythmias. as well as A second cardiac signal fragment is obtained when cardiac pacing is suppressed, the second cardiac signal fragment having a second duration equal to the first duration of the first cardiac signal fragment; Based on the morphological analysis, it is determined whether the second cardiac signal fragment is classified as a ventricular tachyarrhythmia; The pacing period is terminated when the second cardiac signal fragment is classified as a ventricular tachyarrhythmia based on the morphological analysis. as well as In response to the second cardiac signal fragment not being classified as a ventricular tachyarrhythmia based on the morphological analysis, the therapeutic delivery circuit is controlled to resume delivery of cardiac pacing pulses.

12. The medical device according to any one of claims 1 to 11, wherein the control circuitry is further configured to perform the morphological analysis of the first cardiac signal segment by: The amplitude is determined based on the first cardiac signal segment; When the amplitude is less than the amplitude threshold, cardiac arrest analysis is performed to classify the first cardiac signal segment as either cardiac arrest or a non-ventricular tachyarrhythmia; and When the amplitude is at least the threshold amplitude, a rapid arrhythmia analysis is performed to classify the first cardiac signal segment as either a ventricular tachyarrhythmia or a non-ventricular tachyarrhythmia.

13. The medical device of claim 12, wherein the control circuitry is further configured to perform the rapid arrhythmia analysis of the first cardiac signal segment by determining at least one of the following: The average time period from the first cardiac signal segment; and The spectral width of the first cardiac signal segment.

14. The medical device according to any one of claims 1 to 13, wherein the control circuit is further configured to: Prior to obtaining the first cardiac signal segment, previous cardiac signal segments are obtained from the plurality of cardiac signal segments; Based on the morphological analysis performed on the previous cardiac signal fragment, it was determined that the previous cardiac signal fragment was classified as either a non-ventricular tachyarrhythmia or cardiac arrest; and In response to reaching the first required number of tachyarrhythmic intervals, the preceding cardiac signal fragment is classified as either a non-ventricular tachyarrhythmia or cardiac arrest and the rejection rule is satisfied to suppress the detection of ventricular tachyarrhythmias.

15. The medical device according to claim 1, wherein: The control circuit is also configured to determine, based on analysis of the plurality of cardiac signals sensed by the sensing circuit after the initiation of charging of the capacitor, that the criteria for stopping treatment are met. The treatment delivery circuit is also configured to stop the delivery of treatment in response to the control circuit determining that the treatment termination criteria are met; The control circuit is further configured to: Determine from the ventricular sensing event signal the number of tachyarrhythmic intervals that reach a threshold for re-detecting the ventricular tachyarrhythmia after the delivery of the treatment is discontinued; and The ventricular tachyarrhythmia is re-detected in response to reaching the threshold number of tachyarrhythmic intervals and one of the following: a) Determine if the rejection rule used to suppress the detection of rapid arrhythmias is satisfied; or b) Determine that the rejection rule for suppressing the detection of tachyarrhythmias is met, and that a second cardiac signal fragment obtained from the plurality of cardiac signals is classified as a ventricular tachyarrhythmia based on the morphological analysis.

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