Medical devices and methods for delayed tachyarrhythmia detection

Abstract

A medical device is configured to sense one or more cardiac electrical signals and sense a ventricular event signal from the one or more cardiac electrical signals. The medical device can determine that the one or more cardiac electrical signals satisfy a tachyarrhythmia detection criterion, and in response to satisfying the tachyarrhythmia detection criterion, apply a delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of groups of a plurality of sensed ventricular event signals. In response to satisfying the detection delay criterion, the medical device can delay detection of a tachyarrhythmia.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 593,934, filed October 27, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to medical devices and methods for detecting tachyarrhythmias, which may include delaying the detection of tachyarrhythmias and / or delaying the initiation of anti-tachyarrhythmic treatment. 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 electrical signals from a patient's heart. Medical devices can also sense electrical signals from the heart chambers and deliver electrical stimulation therapy to the heart chambers using electrodes carried by transvenous medical leads that position the electrodes within the patient's heart.

[0004] A cardiac pacemaker or cardiopulmonary bypass device (CPAD) 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 cardiopulmonary bypass or defibrillation 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 are typically of high signal strength and quality for reliably sensing 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 detecting tachyarrhythmias and determining the need for delivery of CV / DF shocks. The medical device may be configured to perform tachyarrhythmia detection techniques including delaying the detection of the tachyarrhythmia and / or delaying the initiation of anti-tachyarrhythmic therapy to allow oversensitization or other transient events to subside prior to tachyarrhythmia detection. A medical device operating according to the techniques disclosed herein is configured to detect ventricular tachyarrhythmias or ventricular fibrillation (VT / VF) and, in response to the detection of VT / VF, initiate the delivery of anti-tachycardia pacing (ATP) and / or initiate charging of a high-voltage capacitor to deliver a CV / DF shock. When a rapid ventricular rate meeting a first VT / VF detection criterion is detected, unnecessary anti-tachyarrhythmic therapy is avoided by applying a detection delay criterion. When the detection delay criterion is met, the medical device may delay VT / VF detection and / or delay the initiation of ATP and / or CV / DF shock delivery. ATP and / or CV / DF shock delivery can be avoided when any transient or intermittent hypersensitivity is present and subsequently subsides during the delay interval, or when a non-sustained rhythm spontaneously terminates. When the detection delay criterion is not met, the medical device can detect VT / VF with high confidence and continue to initiate anti-tachyarrhythmic therapy delivery, for example, by delivering ATP and / or initiating charging of a high-voltage capacitor for CV / DF shock delivery.

[0006] In one example, this disclosure provides a medical device including a sensing circuit configured to sense one or more cardiac electrical signals and sense ventricular event signals from the one or more cardiac electrical signals. The medical device may include control circuitry in communication with the sensing circuitry. The control circuitry may be configured to determine that one or more cardiac electrical signals meet a tachyarrhythmia detection criterion, apply a first delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of sets of ventricular event signals sensed by the sensing circuitry, and determine that a detection delay criterion is met by determining that at least a threshold number of sets of the plurality of ventricular event signals sensed by the sensing circuitry meet at least the first delay criterion. In response to meeting the detection delay criterion, the control circuitry may delay the detection of a tachyarrhythmia based on meeting the tachyarrhythmia detection criterion. The medical device may include a treatment delivery circuitry configured to initiate anti-tachyarrhythmia treatment when the control circuitry detects a tachyarrhythmia, and the initiation of anti-tachyarrhythmia treatment is also delayed when the detection of the tachyarrhythmia is delayed by the control circuitry.

[0007] In another example, this disclosure provides a method comprising: sensing one or more cardiac electrical signals; sensing ventricular event signals from the one or more cardiac electrical signals; and determining that the one or more cardiac electrical signals meet a tachyarrhythmia detection criterion. The method may further comprise applying a first delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of sets of sensed ventricular event signals. The method may further comprise determining that a detection delay criterion is met by determining that at least a threshold number of sets of sensed ventricular event signals in the plurality of sets meet at least the first delay criterion. The method may include: delaying the detection of a tachyarrhythmia based on meeting the tachyarrhythmia detection criterion in response to meeting the detection delay criterion; and initiating anti-tachyarrhythmic treatment in response to the detection of a tachyarrhythmia, wherein the initiation of anti-tachyarrhythmic treatment is also delayed when the detection of the tachyarrhythmia is delayed.

[0008] In yet 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 one or more cardiac electrical signals; sense ventricular event signals from the one or more cardiac electrical signals; and determine that the one or more cardiac electrical signals meet a tachyarrhythmia detection criterion. These instructions may also cause the medical device to: apply a delay criterion to one or more cardiac electrical signals sensed during each of multiple sets of sensed ventricular event signals; and determine that a detection delay criterion is met by determining that at least a threshold number of sets of sensed ventricular event signals meet at least a delay criterion. These instructions may also cause the medical device to: delay the detection of a tachyarrhythmia based on meeting the tachyarrhythmia detection criterion in response to meeting the detection delay criterion; and initiate anti-tachyarrhythmia treatment when a tachyarrhythmia is detected, wherein the initiation of anti-tachyarrhythmia treatment is also delayed when the detection of the tachyarrhythmia is delayed.

[0009] 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

[0010] 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.

[0011] Figures 2A to 2C Is it implanted in a position with Figures 1A to 1BThe diagram shows a concept of a patient with an ICD system arranged in different implantation configurations.

[0012] Figure 3 It is a conceptual diagram based on an example ICD.

[0013] Figure 4 It can be included based on an example. Figure 3 The diagram shows a conceptual representation of the circuitry in the sensing circuit of the ICD.

[0014] Figure 5 This is a conceptual diagram of the operational state of an ICD used to detect VT / VF and deliver treatment in response to VT / VF detection, based on some examples.

[0015] Figure 6 This is a flowchart of a rapid arrhythmia detection method that can be performed by a medical device, based on some examples.

[0016] Figure 7 This is a flowchart of a rapid arrhythmia detection method that can be performed by a medical device, according to another example.

[0017] Figure 8 This is a flowchart of a method, based on some examples, that can be performed by a medical device to determine when a detection delay criterion is met.

[0018] Figure 9 This is a flowchart of a method for determining when a detection delay criterion is met, based on some examples.

[0019] Figure 10 This is a flowchart of a method for determining when an oversensing criterion for detection delay is met, based on some examples.

[0020] Figure 11 It is a conceptual diagram of a buffer allocated in the memory of a medical device, based on an exemplary example, to facilitate the determination, according to some examples, when a detection delay criterion for the detection of delayed rapid arrhythmias is met.

[0021] Figure 12 This is a flowchart of a method for determining when the morphological criteria for rapid arrhythmias are met, based on some examples.

[0022] Figure 13 This is a flowchart of a method for adjusting a rapid arrhythmia interval counter, based on some examples. Detailed Implementation

[0023] Generally, this disclosure describes medical devices and techniques for detecting tachyarrhythmias and controlling anti-tachyarrhythmic treatment. In various examples, the medical device performing the techniques disclosed herein may be included in an ICD system capable of sensing cardiac electrical signals, detecting tachyarrhythmias based on processing and analysis of the sensed cardiac electrical signals, and delivering electrical stimulation therapy for treating the tachyarrhythmias. 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 are generally not in close contact with myocardial tissue, for example, within the heart or within the pericardium. In other examples, the techniques disclosed herein can be performed by an ICD coupled to a transvenous cardiac lead carrying implantable electrodes that can be positioned within a vein but outside the heart, such as in an internal thoracic vein, jugular vein, or other vein, for sensing cardiac electrical signals and delivering cardiac pacing pulses. In other examples, the techniques disclosed herein can be performed by an ICD coupled to a transvenous lead carrying implantable electrodes that can be positioned within the heart, such as within the atria and / or ventricles, for sensing cardiac electrical signals and delivering cardiac pacing pulses. In other examples, the techniques disclosed herein can be performed by an ICD coupled to a lead carrying implantable electrodes that can be positioned within the pericardium, such as in an epicardial location.

[0024] 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 tachyarrhythmias, 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 1BDescribed within the context of an ICD system 10, which is capable of providing a high-voltage CV / DF shock and / or cardiac pacing pulse in response to the detection of tachyarrhythmias based on processing of sensed cardiac electrical signals. The techniques for detecting tachyarrhythmias 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 tachyarrhythmias can be implemented in a variety of medical devices, including external or implantable cardiac monitors, pacemakers, and ICDs.

[0025] 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 instances, the housing 15 of the ICD 14 may include multiple electrodes on an external portion of the housing. The external 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.

[0026] 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 accommodate 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.

[0027] The elongated lead body 18 has: a proximal end 27 including a lead connector (not shown) configured to connect to the ICD connector assembly 17; and a distal portion 25 including one or more electrodes. Figure 1A and Figure 1BIn 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.

[0028] 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 large surface area for delivering high-voltage electrical stimulation pulses compared to pacing and sensing electrodes 28 and pacing and sensing electrodes 30. However, as a complement to or alternative to high-voltage CV / DF 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.

[0029] Electrodes 28 and 30 are relatively small surface area electrodes that can be used in a sensing electrode vector 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 instances, electrodes 28 and 30 may provide pacing functionality only, sensing functionality only, or both.

[0030] 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. One or more 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 and, 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, such as ATP or CV / DF shocks.

[0031] 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 positions shown. In other examples, lead 16 may comprise fewer or more pacing / sensing electrodes and / or defibrillator electrodes than in the example shown herein.

[0032] 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) subcutaneously or submuscularly over the thorax 32. Near the xiphoid process 20, lead 16 bends or turns upward, subcutaneously or submuscularly, above the sternum and / or sternum 22. Although in Figure 1AThe 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 positioning 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 positions of the electrodes 24, 26, 28, and 30.

[0033] 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.

[0034] 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.

[0035] In the example shown, the lead body 18 includes a curved distal portion 25 with two "C"-shaped curves that together resemble the Greek letter Epsilon. The defibrillator electrodes 24 and 26 are each carried by 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 defibrillator electrodes 24 and 26 are laterally offset from the pacing / sensing electrodes 28 and 30.

[0036] Other examples of cardiovascular external leads comprising one or more defibrillation electrodes and one or more pacing and sensing electrodes carried by a curved, serpentine, wavy, or serrated distal portion of a lead body 18, which are generally disclosed in U.S. Patent No. 10,675,478 (Marshall et al.), and which are incorporated herein by reference in their entirety, are generally disclosed. However, 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.

[0037] The ICD 14 analyzes cardiac electrical signals received from one or more sensing electrode vectors to monitor abnormal 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 according to the techniques disclosed herein to monitor ventricular tachyarrhythmias. The ICD 14 can generate and deliver electrical stimulation therapy in response to the detection of a tachyarrhythmia (e.g., VT or VF (VT / VF)) using a therapeutic delivery electrode vector selectable from any of the available electrodes 24, 26, 28, 30, and / or housing 15. The ICD 14 can deliver ATP in response to VT detection and, in some cases, can deliver ATP before or during high-voltage capacitor charging to attempt to avoid the need for CV / DF shock delivery. If ATP fails to terminate VT or when VF is detected, ICD 14 may deliver one or more CV / DF shocks via one or both of defibrillation electrodes 24 and 26 and / or housing 15.

[0038] 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.

[0039] ICD 14 is shown subcutaneously implanted along the left side of patient 12 along thoracic 32. In some instances, 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 / thoracic 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.

[0040] 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 cardiovascular external leads 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 substernal positioning), and may not necessarily be in close contact with myocardial tissue. Cardiovascular external leads can also be referred to as "non-transvenous" leads.

[0041] 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.

[0042] 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.

[0043] 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 send data to ICD 14, including programmable parameters for controlling cardiac event signal sensing, rapid 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.

[0044] Can use Bluetooth, etc. ® A communication link 42 is established between the ICD 14 and the external device 40 via a radio frequency (RF) link, such as Wi-Fi, Medical Implantable Communication Service (MICS), or other RF or communication frequency bandwidth or communication protocol. 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.

[0045] 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 for detecting tachyarrhythmias and controlling anti-tachyarrhythmic treatment according to the techniques disclosed herein into ICD 14.

[0046] 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 external cardiovascular lead 16 of the system 10 is at least partially implanted below the sternum 22 of the patient 12. The lead 16 extends subcutaneously or submuscularly from the ICD 14 toward the xiphoid process 20, and bends or turns within the anterior mediastinum 36 and extends upwards at a substernal location near the xiphoid process 20 (see [link to ICD 10]). Figure 2C ).

[0047] 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”.

[0048] 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.

[0049] In the various example implantation sites of leads 16 and electrodes 24, 26, 28, and 30 shown and described herein, the cardiac signals sensed by the ICD 14 may have relatively low and / or variable signal strength (e.g., caused by changes in posture, breathing, or other body movement). The sensed cardiac signals may be contaminated by skeletal muscle electrical activity or other non-cardiac electrophysiological signals, EMI, or other environmental noise, which in some cases may include lead-related noise (e.g., due to lead breakage or poor lead connection). Oversensing of P waves, T waves, skeletal muscle electrical activity, EMI, or other non-cardiac noise, or oversensing due to highly variable R wave amplitude (e.g., due to changes in patient position and / or patient breathing), may lead to erroneous tachyarrhythmia detection, thereby triggering unnecessary ATP or CV / DF shock delivery. The techniques disclosed herein provide improvements for the detection of tachyarrhythmias by medical devices in that they delay tachyarrhythmia detection when heart rate-based ventricular tachyarrhythmia detection criteria are met but tachyarrhythmia morphology criteria are not.

[0050] Cardiac signal oversensing occurs when a P wave or T wave is oversensed as an R wave, or when a wide QRS complex is oversensed twice as two R waves instead of one. Non-cardiac event oversensing occurs when a non-cardiac signal pulse (e.g., skeletal muscle electromyography or EMI) is oversensed as an R wave by the ICD-14. Oversensed cardiac or non-cardiac event signals can be counted as ventricular beats, and when they occur within the rapid arrhythmia detection interval following a previously sensed R wave (or another oversensed signal), they can be counted as VT / VF beats. Therefore, this oversensing can lead to erroneous VT / VF detections.

[0051] However, oversensing can be intermittent or transient, and if ICD 14 applies a tachyarrhythmia detection delay interval when heart rate-based VT / VF detection criteria are met but, for example, no evidence of VT / VF morphology is detected and evidence of oversensing is detected, the oversensing may dissipate or subside. In some cases, supraventricular tachyarrhythmias (SVT) and sinus tachycardia (ST) can be conducted to the ventricles and can be detected as tachyarrhythmias that meet heart rate-based VT / VF detection criteria. Conducted SVT or ST can also be intermittent or transient, and if ICD 14 applies a tachyarrhythmia detection delay interval when heart rate-based VT / VF detection criteria are met but no evidence of VT / VF morphology is detected, the conducted SVT or ST may terminate spontaneously. By providing a tachyarrhythmia detection delay, erroneous VT / VF detection can be avoided when oversensing and / or conducted SVT or ST occur, thereby improving control of VT / VF detection and antitachyarrhythmia therapy delivery. Improvements in the high sensitivity and specificity of VT / VF detection can enhance the performance of medical devices, enabling them to deliver appropriate electrical stimulation therapy for successful treatment of detected VT / VF while avoiding unnecessary anti-tachyarrhythmic treatments, such as ATP and / or CV / DF shock delivery.

[0052] Figure 3 This is based on a conceptual diagram of an example ICD 14. The electronic circuitry is enclosed within a housing 15 (in... Figure 3 The ICD (conceptually shown 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 on demand according to 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.

[0053] The ICD 14 includes control circuitry 80, memory 82, therapy 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 can be made from... Figure 3 The 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.

[0054] Figure 3 The circuitry illustrated represents the functionality included in ICD 14 and may include any discrete and / or integrated electronic circuitry components that implement analog and / or digital circuitry capable of producing the functions attributed herein to ICD 14. The 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, the sensing and analysis of cardiac electrical signals for detecting tachyarrhythmias 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.

[0055] 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 sum, absolute value, difference, extreme value, histogram or memory buffer counting, signal filtering (e.g., bi-second-order filters, differential filters, or other filters), etc. These HSRs may be invoked by the control circuitry firmware when processing and analyzing cardiac signals to detect tachyarrhythmias; these processes may include low-pass filters, differential filters, gradient filters, or other signal processing. As described herein, HSRs may be invoked when control circuitry 80 determines various morphological parameters based on cardiac signals to detect tachyarrhythmias. These HSRs can offload the processing burden associated with firmware and / or software processing to reduce current consumption of power supply 98 and thereby extend the lifespan of ICD 14.

[0056] Various circuits of the ICD 14 may include application-specific integrated circuits (ASICs), electronic circuitry, (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.

[0057] 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.

[0058] 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.

[0059] 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. As further described below, at least one cardiac electrical signal may be received by sensing circuit 86 and transmitted to control circuit 80 for processing and analysis to determine when morphological criteria for detecting tachyarrhythmias or delaying tachyarrhythmia detection are met. In some examples, cardiac electrical signals received within a predetermined or specified time interval containing a trigger Vsense signal may be analyzed to classify signal segments (hereinafter referred to as “pulsating signal segments”) with high confidence as having a VT / VF pulsating morphology, thereby avoiding delayed VT / VF detection when the probability of erroneous VT / VF detection is relatively low. In the illustrated example, 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.

[0060] When included, each sensing channel 83 and 85 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, as combined... 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.

[0061] 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.

[0062] 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, based on the RRI, the control circuit 80 may determine whether heart rate-based VT / VF detection criteria are met. 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.

[0063] Sensing circuit 86 in Figure 3 The image is shown 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 (when the sensing electrodes are located outside the patient's heart) to control circuitry 80 for signal morphology analysis. Three distinct sensing electrode vectors selected from available electrodes 24, 26, 28, and 30 and housing 15 can be used to receive the three cardiac electrical signals sensed by sensing circuitry 86. In other examples, sensing circuitry 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. One or both of the two signals may be transmitted to control circuitry 80 as a multi-digit ECG signal (or an ECG “EGM” signal when the sensing electrodes are positioned within the heart). Control circuitry 80 uses the multi-digit ECG signal to perform morphological analysis on predetermined time segments of the ECG signal to detect tachyarrhythmias or delayed tachyarrhythmias according to the techniques disclosed herein. However, it should be understood that the techniques disclosed herein can be implemented using sensing circuitry 86, which is configured to sense one or more cardiac electrical signals via one or more sensing channels. For example, a single sensing channel 83 or 85 for transmitting the Vsense signal to control circuitry 80 may be used to perform the sensing and signal morphological analysis of the ventricular event signal described herein. In some examples, when the sensing channel is configured to sense the ventricular event signal and transmit the ECG signal (or ECG “EGM” signal) to control circuitry 80 for signal morphological analysis, morphological sensing channel 87 may be optional.

[0064] 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 delivery of electrical stimulation 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 continuously received Vsense signals within the channels (and in some cases, from the delivered pacing pulse to the Vsense signal). The control circuit 80 can pass the RRI to the arrhythmia detection circuit 92 to determine and count the VF / VF intervals.

[0065] Control circuitry 80 may include arrhythmia detection circuitry 92 configured to analyze the RRI received from timing circuitry 90 and cardiac electrical signals received from morphological signal channel 87 to detect tachyarrhythmias. Arrhythmia detection circuitry 92 may be configured to detect ventricular tachyarrhythmias based on the sensed cardiac electrical signals meeting VT / VF detection criteria. For example, control circuitry 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. The RRI shorter than the tachyarrhythmia detection interval is referred to as the "tachyarrhythmia interval" or "VT / VF interval." In some examples, a first tachyarrhythmia detection criterion may be met when a threshold number of tachyarrhythmia intervals are reached. As further described below, when the first tachyarrhythmia detection criterion is met, the arrhythmia detection circuit 92 may apply a detection delay criterion to determine whether tachyarrhythmia detection (or at least anti-tachyarrhythmia treatment) should be delayed. The detection delay criterion may include an oversensing criterion, a SVT criterion, and / or a VT / VF beat morphology criterion. The VT / VF beat morphology criterion may be applied to sensed cardiac signal waveforms to detect morphological evidence highly correlated with the presence of VT / VF. The detection delay criterion may not be met when cardiac signal analysis, based on morphological analysis of the cardiac signal, indicates a high probability of a true VT / VF beat. However, the detection delay criterion may be met when there is evidence of oversensing based on analysis of cardiac electrical signals and the VT / VF beat morphology criterion is not met. In some examples, the detection delay criterion may be met when the SVT criterion is met and the VT / VF beat morphology criterion is not met. When the detection delay criterion is met, the arrhythmia detection circuit 92 may delay VT / VF detection when the first (e.g., heart rate-based) tachyarrhythmia detection criterion is met. VT / VF detection may be delayed by at least a specified detection delay interval. After the detection delay interval, the arrhythmia detection circuit 92 may reapply the detection delay criteria to determine whether VT / VF detection should be performed or delayed again, for example, until the maximum time delay. The following example combines... Figures 6 to 11 The method for determining when the detection delay criterion is met is further described.

[0066] The arrhythmia detection circuit 92 may be implemented in the control circuit 80 as hardware, software, and / or firmware for processing and analyzing signals received from the sensing circuit 86 to detect tachyarrhythmias. The arrhythmia detection circuit 92 may identify signal pulses for determining amplitude and / or pulse interval measurements of cardiac electrical signal segments for detecting tachyarrhythmias, as further described below. In some examples, the arrhythmia detection circuit 92 may be configured to determine morphological measures of cardiac signal segments in relation to signal amplitude, signal width, and number of signal pulses. These morphological measures may be compared to criteria used for detecting or delaying VT / VF to control the treatment delivery circuit 84, thereby appropriately initiating (or delaying) ATP and / or CV / DF electrical shock therapy.

[0067] 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 the detection interval zones are 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 350ms to 420ms, or programmed to, for example, 400ms. RRIs shorter than the VT detection interval but greater than or equal to the VF detection interval can be counted by the VTI counter. When the corresponding VTI or VFI counter (or the combined VT / VF interval counter) reaches the threshold number (NID) of the detection interval, the criteria for detecting VT or VF can be met.

[0068] For example, the NID required to detect VT may require the VTI counter to reach 18 VTIs, 24 VTIs, 32 VTIs, or other selected NIDs. In some examples, the VTIs 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, if other criteria for rejecting or delaying VT / VF detection are not met, the arrhythmia detection circuit 92 can detect ventricular tachyarrhythmias, as further described below. NID can be programmable and is unlimited in the range from as low as 12 to as high as 120. A VTI counter or VFI counter can reach the corresponding NID when VTI or VFI is detected sequentially or discontinuously from a specified number of recent RRIs. 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. In some examples, heart rate-based VT / VF detection criteria may be met when an NID is reached (or exceeded). However, when other VT / VF rejection criteria or detection delay criteria are met, the control circuit 80 may not detect VT / VF based on reaching an NID, as further described below.

[0069] 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 criteria, are met before detecting VT or VF based on achieving NID. To support these additional analyses, sensing circuit 86 can transmit digitized ECG (or EGM) signals to control circuit 80 (e.g., from morphology signal channel 87) for morphological analysis performed by the arrhythmia detection circuit 92 to detect and differentiate heart rhythms. The cardiac electrical signals received by morphology signal channel 87 (and / or sensing channels 83 and / or 85) can 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 are included in sensing circuit 86 for storage in memory 82. Memory 82 may include one or more loop buffers to temporarily store digital cardiac signal segments used for analysis performed by control circuit 80. The control circuit 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 in order 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).

[0070] 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.

[0071] 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 across 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. In some cases, treatment delivery circuit 84 may be configured to receive a signal from external device 40 during ICD implantation or subsequent testing procedures. Figure 1A When programming commands are executed, electrical stimulation pulses, such as T-wave shocks or induced pulse trains, are delivered to induce tachyarrhythmias.

[0072] 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.

[0073] 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) to communicate. 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.

[0074] Figure 4 It is based on some examples and can be included in Figure 3 A conceptual diagram of the circuitry in the sensing circuit 86 is shown. The sensing circuit 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 circuit included in the sensing circuit 86, the corresponding sensing electrode vector including at least one electrode carried by a cardiovascular external 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, 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.

[0075] 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.

[0076] 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 rapid arrhythmia classification of a segment of cardiac electrical signal occurs, for use in controlling when VT / VF detection is performed or delayed, as further described below. For example, one or more morphological measures may be determined to identify the VT / VF pulsation morphology of the sensed signal waveform. If a threshold percentage of the sensed signal waveform is identified by control circuit 80 as having a VT / VF pulsation morphology, the detection delay criterion may not be met.

[0077] Control circuitry 80 may utilize morphological signals received from morphological signal channel 87 to perform various morphological correlation analyses to support VT / VF detection or delayed VT / VF detection for initiation of anti-tachyarrhythmia therapy. For example, control circuitry 80 may perform morphological matching analysis involving wavelet transform to determine a morphological matching score between the sensed signal waveform received from morphological sensing channel 87 and a morphological template established for a normally conducted R wave. Morphological matching analysis may be performed to distinguish between conducted SVT or ST and VT / VF. In some examples, a VT / VF rejection rule may be satisfied when the SVT criterion is met based on morphological matching analysis, thereby preventing control circuitry 80 from detecting VT / VF upon reaching NID. Example methods for performing morphological matching analysis are generally disclosed in U.S. Patent No. 8,521,268 (filed May 10, 2011 by Zhang et al.), which is incorporated herein by reference in its entirety.

[0078] Additionally or alternatively, control circuitry 80 may perform morphological analysis of an n-second cardiac signal segment, which may be obtained independently of the Vsense signal sensed by sensing channel 83 and / or sensing channel 85. When the VTI or VFI counter is continuously increasing but no Vsense signal has been sensed during a long pause (indicating insufficient sensing of a possible R wave or fibrillation wave), morphological analysis of a buffered n-second signal segment, independent of any timing or number of Vsense signals, may be performed to detect morphological evidence of VT / VF. When arrhythmia detection circuitry 92 detects morphological evidence of VT / VF based on analysis of an n-second segment (e.g., a three-second segment) before reaching NID, control circuitry 80 may increase the sensitivity of R wave sensing by first sensing channel 83 and / or second sensing channel 85. PCT International Publication No. WO2023 / 159031 (Heinks et al.) generally discloses examples of methods for performing morphological analysis of an n-second cardiac signal segment for detecting VT / VF and / or controlling the sensing sensitivity of sensing channels 83 and 85, which is incorporated herein by reference in its entirety.

[0079] In other examples, control circuitry 80 may buffer pulsation signal segments that are preceded by a specified number of sampling points (or time intervals) and delayed by a specified number of sampling points (or time intervals) from the Vsense signal, enabling analysis of individual pulsation waveforms associated with the Vsense signal. Based on the morphological characteristics of the individual waveform sensed as an R wave, the pulsation signal segments can be classified as non-VT / VF morphological pulsations or VT / VF morphological pulsations. As further described below, control circuitry 80 can use the classification of pulsation signal segments to determine when the VT / VF pulsation morphology criteria are not met to satisfy the detection delay criteria. It should be noted that the morphological analysis performed on an n-second cardiac signal segment (e.g., which may contain any number of Vsense signals or a 3-second segment without Vsense signals) differs from the VT / VF pulsation morphological analysis performed on the pulsation signal segment, which is used to classify individual Vsense signals as VT / VF morphological pulsations or non-VT / VF morphological pulsations. The Vsense signal triggers the storage of buffered cardiac electrical signals to obtain a pulsating signal segment with a start and end time dependent on the timing of the Vsense signal. This n-second cardiac signal segment has a start and end time independent of the Vsense signal and can be analyzed to demonstrate the presence of rapid arrhythmic waveform characteristics in the signal without using any Vsense signal timing.

[0080] For these purposes, in some examples, the sensing electrode vector coupled to the morphological 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 morphological 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 morphological 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 morphological signal channel 87. In this case, sensing channels 83 or 85 and the morphological signal channel 87 may be combined or include shared components such that the morphological signal and the Vsense signal can be output from one sensing channel to the control circuitry 80.

[0081] The first sensing channel 83 and the second sensing channel 85 can each receive cardiac electrical signals to sense ventricular event signals 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 the 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.

[0082] 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.

[0083] 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.

[0084] 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).

[0085] The R-wave sensing threshold can be a multi-stage 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-stage 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 falls to a second sensing threshold that maintains a second fall interval until it expires, 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 step down to the second sensing threshold. Following the second fall interval, the sensing threshold decreases to a minimum sensing threshold, which may be equal to the programmed sensitivity or an enhanced sensitivity based on morphological analysis of an n-second cardiac signal segment (as described in PCT International Publication WO2023 / 159031 (Heinks et al.), incorporated above). The enhanced sensitivity may be a sensitivity amplitude setting that is lower than the programmed sensitivity amplitude setting in amplitude (e.g., in millivolts). The sensitivity may also be referred to herein as the “sensing floor” because it represents the minimum amplitude of the 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 may decrease to the sensing floor in a single step, for example, to the programmed sensitivity or an enhanced sensitivity (an amplitude setting lower than the programmed sensitivity).

[0086] 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 in 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 is reached (e.g., equal to the sensitivity setting), 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 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.

[0087] 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.

[0088] The broadband filtered digital cardiac electrical signal 78 output from the morphology signal channel 87 can be passed to the control circuit 80 to perform morphology-based cardiac signal analysis according to the techniques disclosed herein. In some examples, the digital cardiac electrical signal 78 is passed to a rectifier 75, and the rectified broadband filtered signal 79 is passed to the control circuit 80 for processing and analysis. In some cases, both the filtered unrectified signal 78 and the rectified signal 79 are passed from the morphology signal channel 87 to the control circuit 80 for determining the morphological characteristics of the ECG signal.

[0089] 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 one or more sensing channels for generating a Vsense signal in response to an R-wave sensing threshold exceeding, and may include one or more morphological signal channels. In other examples, a wideband filtered morphological signal may be passed from one sensing channel to control circuit 80, which is configured to generate a Vsense signal and pass the morphological signal to control circuit 80 to perform cardiac signal segment analysis 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.

[0090] Figure 5This is a conceptual diagram 100 illustrating the operational states of an ICD 14 in relation to VT / VF detection and delivery of anti-tachyarrhythmic therapy, based on some examples. At box 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 Vsense signals from sensing circuitry 86 and determines RRIs, which can be used to update the VTI and VFI counters. In some examples, Vsense signals are received from each of sensing channels 83 and 85. Each sensing channel 83 and 85 can initially sense ventricular event signals according to a programmed sensitivity for each respective sensing channel, which can be user-programmed or a default sensitivity setting.

[0091] The Relative Indicator (RRI) can be determined by control circuitry 80 between consecutively received Vsense signals in each sensing channel 83 and 85. Control circuitry 80 can compare the RRI with the VT detection interval region or threshold interval (when VT detection is enabled) and / or the VF detection interval region or threshold interval to identify the VTI and / or VFI. When the RRI is determined to be a VTI or VFI, a corresponding VTI counter or VFI counter (and / or a combined VT / VF interval counter) is designated to increment for counting the VTI and VFI identified for the respective sensing channel 83 or 85. Therefore, each sensing channel 83 and 85 (when including two sensing channels) can 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 ICD 14, allowing only the VFI counter to be used to track the VFI of each sensing channel 83 and 85. Furthermore, it should be understood that two sensing channels are not required to perform the techniques disclosed herein for determining when to delay VT / VF detection, which triggers anti-tachyarrhythmic therapy when the VTI or VFI counter reaches NID. Figure 5 Combination Figure 4 The example sensing circuit 86 shown is described for illustration purposes. This sensing circuit has two sensing channels 83 and 85 that transmit the Vsense signal to the control circuit 80. In other examples, a single sensing channel 83 or 85 may be provided in the sensing circuit 86 for transmitting the Vsense signal to the control circuit 80 to determine the RRI and count the VTI and / or VFI.

[0092] When the VTI or VFI counter of at least one sensing channel 83 or 85 reaches the NID required for detecting VT or VF, ICD 14 may transition (as indicated by arrow 103) to the relevant tachyarrhythmia detection state 2 in box 104. At box 104, in response to reaching the NID, ICD 14 may transition to the relevant tachyarrhythmia suspected state 2, also referred to herein as "relevant state 2" or simply "state 2".

[0093] When two (or more) sensing channels are provided, control circuitry 80 may identify one sensing channel 83 or 85 as a reliable sensing channel for VT / VF detection. For example, when the VTI / VFI counter of a sensing channel 83 or 85 reaches NID, control circuitry 80 may evaluate the relative timing of the Vsense signal and / or the shape matching score of the sensed signal waveform to select one 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 need to reach NID (via the associated VTI / VFI counter) in order to transition from state 1 of block 102 to state 2 of block 104. If the sensing channel 83 or 85 identified as a reliable sensing channel for VT / VF detection is not a sensing channel associated with a VTI / VFI counter that has reached NID, control circuitry 80 may remain in the unrelated sensing state 1 of block 102. Control circuitry 80 may perform a method during irrelevant sensing state 1 to sense ventricular event signals using two sensing channels 83 and 85, select a reliable sensing channel for VT / VF detection, and determine when criteria for transitioning to relevant state 2 of box 104 are met, as generally disclosed in U.S. Patent Application Publication No. 2023 / 0100431 (Liu et al.), filed August 29, 2022. Other heart rate-based criteria may be applied to the Vsense signal received from sensing circuitry 86 to determine when a first criterion for VT / VF detection is met, thereby causing a transition to state 2 of box 104.

[0094] Furthermore, in some examples, control circuitry 80 may rely on heart rate-based and / or morphology-based criteria to induce the transition from state 1 to state 2. As described above, when the VTI / VFI counter keeps increasing but has not yet reached NID, insufficient sensing of the R wave or fibrillation wave may prevent reaching NID. Control circuitry 80 may be configured to analyze an n-second cardiac signal segment to detect morphological evidence of VT / VF, independent of the timing of the Vsense signal received from sensing channels 83 or 85. If morphological evidence of VT / VF is detected, in some examples, control circuitry 80 may transition from irrelevant state 1 to relevant state 2. Thus, a first criterion for detecting VT / VF may be met based on RRI and / or morphological analysis of the sensed cardiac signal. As an example, morphological measures determined for detecting evidence of VT / VF in an n-second cardiac signal segment may include low slope content, spectral width, and average period. An example method for performing cardiac electrical signal morphology analysis is generally disclosed herein and generally described in U.S. Patent Application Publication No. 2023 / 0148939 (Aranda Hernandez et al., filed October 7, 2022), which can be used to determine when a first VT / VF detection criterion is met to cause a transition from state 1 to state 2.

[0095] Various criteria can be applied to determine the RRI based on the Vsense signal received from sensing channels 83 and / or 85 and / or the morphological signal received from the morphological sensing channel 87, to transition from the unrelated sensing state of box 102 to the relevant sensing state of box 104. It should be understood that the transition from state 1 of box 102 to state 2 of box 104 may not represent a VT / VF detection that will result in the scheduling or initiation of ATP and / or CV / DF electrical stimulation therapy. Instead, the first criterion for VT / VF detection may be met during unrelated sensing state 1, enabling and performing additional cardiac signal analysis in relevant state 2. The additional cardiac signal analysis performed in state 2 may require greater processing power and burden than the first VT / VF detection criteria applied in unrelated state 1. During relevant tachyarrhythmia detection state 2 of box 104, control circuitry 80 may suspect a possible VT / VF episode based on the attainment of NID (as an example of meeting the first VT / VF detection criteria), causing a transition to state 2. However, while operating in relevant state 2, control circuit 80 may perform additional cardiac signal analysis to determine whether additional criteria for detecting VT / VF are met.

[0096] For example, control circuit 80 may determine that a VT / VF detection criterion is met when any one or more VT / VF rejection rules are not met. Control circuit 80 may apply one or more VT / VF rejection rules that, when met, will prevent VT / VF detection and prevent the transition from state 2 to charging state 3 of block 106. One or more VT / VF rejection rules (also referred to herein as “rejection rules”) may be applied to Vsense signals and / or morphological signals received from sensing circuit 86, which, for example, involves detecting evidence of ST, SVT, EMI, skeletal muscle noise (also referred to herein as “myoelectric potential noise”), P-wave oversensing (PWOS), and / or T-wave oversensing (TWOS). If no VT / VF rejection rule is met and the NID for VT / VF detection is satisfied, control circuit 80 may apply a detection delay criterion before transitioning to charging state 3 of block 106, for example, as described below. Figure 6 As described. When the detection delay criteria are met (as indicated by arrow 105), VT / VF detection that leads to the transition from relevant state 2 in box 104 to charging state 3 in box 106 (at which point anti-tachyarrhythmia treatment is initiated) may be delayed to avoid erroneous VT / VF detection. The detection delay allows time for transient or self-limiting SVT, intermittent non-cardiac noise, and / or excessive sensing of cardiac events to dissipate or subside before VT / VF detection and the initiation of anti-tachyarrhythmia treatment.

[0097] If the VT / VF rejection rule is determined to be met during relevant state 2 of box 104, ICD 14 may suspend detection of suspected VT / VF episode and remain in relevant state 2 of box 104. If, based on analysis of the cardiac electrical signals sensed by sensing circuit 86, NID is met, no VT / VF rejection rule is met, and the detection delay criterion is not met, then control circuit 80 may detect VT / VF. Control circuit 80 may then transition to charging state 3 of box 106 upon detection of VT / VF (as indicated by arrow 107). During charging state 3 of box 106, treatment delivery circuit 84 may begin charging a high-voltage capacitor under the control of control circuit 80 in preparation for delivery of CV / DF shocks.

[0098] However, in some cases, when operating in state 2 of box 104, the control circuit 80 may determine whether the termination criteria are met based on analysis of the cardiac electrical signals sensed by the sensing circuit 86 before performing VT / VF detection, provided that all VT / VF detection criteria are met. In response to determining that the termination criteria are met, the control circuit 80 may transition back to state 1 as indicated by arrow 101. The control circuit 80 may determine that the termination criteria are met during state 2 (box 104) when the median RRI or other representative RRI determined based on the Vsense signal received from the sensing circuit 86 after reaching NID is greater than the slow threshold interval. For example, the median RRI may be determined based on the most recent 3 to 30 RRIs or the most recent 12 RRIs. In other examples, the mean, truncated mean, mode, or other representative RRI may be determined instead of the median RRI, and if it is greater than the slow threshold interval, the control circuit 80 may transition back to state 1 (box 102). In various examples, the slow threshold interval can be VTI, VTI plus offset, VFI, VFI plus offset, or a percentage or offset greater than the rhythm cycle length (RCL) determined according to the RRI associated with achieving NID.

[0099] For example, RCL can be determined as the mean or median of a specified number of recent RRIs, which are counted as VT / VF intervals, for example, just before NID is reached. RCL can be calculated by control circuitry 80 as a truncated mean, for example, by determining the average RRI after removing the shortest and / or longest RRIs (up to NID) among the most recent N RRIs. In one example, if the eight RRIs determined after NID is reached are longer than RCL plus an offset (e.g., plus 40ms, 50ms, 60ms, 70ms, or 80ms), control circuitry 80 can detect termination and transition back to irrelevant state 1 (box 102). During relevant sensing state 2 in box 104, a termination condition can be met when the threshold number of RRIs (e.g., 6, 8, 10, 12, or other specified number or percentage) is greater than the slow threshold interval. Upon returning to irrelevant sensing state 1, control circuitry 206 can reset the VTI / VFI counters to zero when the termination condition is met. Multiple methods are available to determine whether a suspected or detected VT / VF episode has terminated before treatment delivery. The techniques disclosed herein for determining when to delay VT / VF detection when operating in the relevant state 2 of box 104 are not limited to specific methods for determining when a sensed cardiac signal meets the termination criteria used to control the transition from state 2 back to state 1.

[0100] In other cases, for example, control circuit 80 may transition back to irrelevant state 1 by detecting one or more normal sinus rhythm (NSR) beats based on an RRI greater than the NSR threshold interval and a relatively high R-wave morphology matching score associated with the RRI (e.g., greater than the NSR matching threshold). When a threshold number of NSR beats are detected, control circuit 80 may reset the VTI / VFI counter to zero, or to a non-zero value, but less than the current VTI / VFI counter value. Since the reset VTI / VFI counter no longer satisfies NID, control circuit 80 may transition from relevant state 2 of block 104 back to irrelevant state 1 of block 102. The following is in conjunction with... Figure 13 A method is described for detecting NSR pulsations to reset one or both of the VTI and / or VFI counters (and combined VTI / VFI counters, if used).

[0101] During charging state 3 of block 106, after VT / VF detection, control circuit 80 can determine whether treatment discontinuation criteria are met based on analysis of cardiac electrical signals sensed by sensing circuit 86. Control circuit 80 can 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 can discontinue CV / DF shock treatment if 4 of the most recent 5 RRIs are at least 60 ms longer than the RCL (or other offset). In another example, treatment discontinuation criteria are met when at least 4 of the 5 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 can 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. It should be recognized that multiple treatment discontinuation criteria can be defined and applied by control circuitry 80 to the RRI until CV / DF shock delivery to determine if the rhythm is slowed, thus justifying discontinuation of the CV / DF shock.

[0102] When the treatment abortion criteria are met during charging state 3 in block 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 block 110. The operation during re-detection state 5 is further described below.

[0103] In some examples, the treatment delivery circuit 84 may be configured to deliver one or more ATP treatment sequences during high-voltage 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 during or upon completion of capacitor charging (according to any of the examples above). Although Figure 5 Not explicitly 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.

[0104] When capacitor charging is completed before the criteria for discontinuing treatment (or terminating treatment) are met to deliver a CV / DF shock during charging state 3 (box 106), control circuitry 80 may transition to shock delivery state 4 of box 108. Treatment delivery circuitry 84 may deliver a CV / DF shock after transitioning to state 4. Treatment delivery circuitry 84 may be controlled by control circuitry 80 to synchronize the CV / DF shock with the patient’s inherent heart rhythm, for example, based on the timing of a received Vsense signal. The CV / DF shock may be synchronized with a Vsense signal received outside the refractory period. The CV / DF shock may be delivered when a specified time interval after charging is completed expires. In some cases, the criteria for discontinuing treatment may be met after capacitor charging is completed but before delivering the CV / DF shock, for example, while waiting for a synchronization event during shock delivery state 4.

[0105] 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 circuitry 80 may determine that the treatment discontinuation criteria are met after capacitor charging is complete. Control circuitry 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 begun, if the treatment discontinuation criteria are met before the delivery of a CV / DF shock, control circuitry 80 may transition to re-detection state 5 of block 110 without delivering a CV / DF shock. In other examples, a CV / DF shock may be delivered during state 4, not necessarily synchronized with the patient's inherent heart rhythm.

[0106] After shock delivery (or when the treatment discontinuation criteria are met before shock delivery), control circuitry 80 may transition to re-detection state 5 at block 110. Control circuitry 80 may re-detect VT / VF when a reduced NID is met after shock delivery or after CV / DF shock is discontinued due to meeting treatment discontinuation criteria. Control circuitry 80 may determine the reduced NID based on a 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 re-detect VT / VF when a reduced NID is met and no VT / VF rejection rules applied during re-detection state 5 are met. The re-detection NID may be, for example, 25%, 30%, 50%, 60%, or 70% of the NID required to transition from irrelevant state 1 to relevant state 2. If the VT / VF re-detection criteria are met in state 5, control circuitry 80 may return to charging state 3 at block 106.

[0107] In some examples, control circuit 80 may determine, according to the techniques disclosed herein, whether a detection delay criterion is met during the re-detection state 5 of block 110. When the detection delay criterion is met, control circuit 80 may delay the re-detection of VT / VF. The maximum delay time for VT / VF detection during re-detection state 5 may be shorter than the maximum delay time for VT / VF detection during the relevant state 2 of block 104. For example, if the maximum detection delay time in state 2 is 30 seconds, the maximum detection delay time in state 5 may be 5 to 20 seconds.

[0108] In other examples, control circuitry 80 may apply the detection delay criterion only during the relevant state 2 of block 104. After VT / VF detection has been performed and control circuitry 80 has progressed to state 5 of block 110 (after delivery or abortion of treatment), control circuitry 80 may re-detect VT / VF without delay based on meeting the VT / VF re-detection criterion, without applying the detection delay criterion. In other examples, control circuitry 80 may apply the detection delay criterion during the re-detection state 5 of block 110, depending on whether the transition to state 5 stems from charging state 3 at the time of treatment abortion or from shock delivery state 4 (block 108) after delivering a CV / DF shock. For example, when control circuitry 80 has transitioned to state 5 because the treatment abortion criterion was met in charging state 3, control circuitry 80 may apply the detection delay criterion during the re-detection state 5 of block 110. After a CV / DF shock has been delivered in state 4 of block 108, control circuitry 80 may not apply the detection delay criterion during the re-detection state 5.

[0109] CV / DF shocks (once or multiple times) can be delivered by the treatment delivery circuit 84 in shock delivery state 4 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. Upon transition to indifferent sensing state 1, the VTI / VFI counter can be reset to zero.

[0110] 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 has previously been increased by setting a lower voltage amplitude as the R-wave sensing limit in response to an n-second cardiac signal segment being classified as VT / VF based on morphological analysis, as generally disclosed in PCT International Publication No. WO2023 / 159031, which is incorporated above). 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 (when a shock is delivered during the shock delivery state of block 108, sensing circuit 86 may be blanked or disabled). The enhanced 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 shock delivery), when treatment discontinuation criteria are met, to synchronize VT / VF shocks, to determine if detection delay criteria are met, and to determine when re-detection criteria are met after shock 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.

[0111] While the detection delay method disclosed herein is described in conjunction with an ICD 14 capable of delivering anti-tachyarrhythmic therapy, it is envisioned that the detection delay method could be incorporated into an implanted or external medical device configured to monitor a patient's heart rhythm to accumulate rhythm data, such as the number of tachyarrhythmia episodes, the duration of tachyarrhythmia episodes, and tachyarrhythmia burden, without necessarily initiating or delivering therapy in response to VT / VF detection. For example, the detection delay method disclosed herein could be implemented in a cardiac monitoring device capable of processing, analyzing, and storing data, which could be transmitted, for example, by telemetry circuitry to an external device, such as... Figure 1A External device 40 is shown. For example, in response to VT / VF detection, control circuitry 80 can control telemetry circuitry 88 to send a signal to alert the patient, clinician, or other caregiver to a detected VT / VF episode. The transmitted data can be used by display unit 54, for example, in a graphical user interface, to generate a display of data related to the detection (and delay detection) of the VT / VF episode. Using the techniques disclosed herein, the accuracy of VT / VF episode data obtained by cardiac monitoring devices can be improved to avoid including erroneous VT / VF episode detections due to intermittent or non-continuous oversensing or supraventricular rhythms, and improvements are provided for dynamic monitoring of the patient to collect important cardiac rhythm data that cannot always be captured during clinic visits, clinician consultations, or relatively short periods of monitoring of the patient over hours, days, or weeks. The detection delay technology disclosed herein further improves cardiac rhythm monitoring technology by reducing human error and alleviating the burden on clinicians or other experts when reviewing collected cardiac signals or data derived from them to differentiate and distinguish supraventricular rhythm episodes, oversensing, and true VT / VF (based on human visual examination of recorded cardiac signals, which may be impractical or infeasible).

[0112] Figure 6 This is a flowchart 150 of a rapid arrhythmia detection method that can be performed by a medical device, based on some examples. For illustration, see reference. Figure 3 The ICD 14 and shown Figure 4 The configuration of the sensing circuit 86 shown is described below. Figure 6At block 152, control circuitry 80 may determine whether a first tachyarrhythmia detection criterion is met based on at least one cardiac electrical signal sensed by sensing circuitry 86. For example, control circuitry 80 may determine that at least one sensing channel 83 or 85 has reached NID. In some cases, NID is achieved based on RRI determined from the Vsense signal of sensing channel 83 or 85 when programmed ventricular sensitivity is used to set an R-wave sensing threshold applied to the sensed cardiac signal. In other cases, NID may be achieved after increasing sensitivity, for example, after using a lower ventricular sensitivity setting adjusted in response to classifying one or more n-second cardiac signal segments as VT / VF. In other examples, control circuitry 80 may determine at block 152 that a first VT / VF detection criterion is met when n-second cardiac signal segments of a threshold number obtained independently of the timing of the Vsense signal and / or VFI are classified as VT / VF based on morphological analysis. Figure 5 In the context of the tachyarrhythmia operating state shown, the control circuit 80 of ICD 14 can operate in irrelevant state 1 at block 152 and can transition to relevant state 2 in response to the first VT / VF detection criterion being met at block 152.

[0113] At block 154, control circuitry 80 can apply a detection delay criterion to one or more sensed cardiac signals to determine whether to detect VT / VF or delay VT / VF detection. When a first VT / VF detection criterion is met, for example, when control circuitry 80 switches to... Figure 5 When the relevant state is 2, the detection delay standard can be applied. In other examples, see the following in conjunction with... Figure 7 As described, before applying the detection delay criterion, the control circuit 80 can apply a second VT / VF detection criterion when transitioning to relevant state 2 in response to meeting the first VT / VF detection criterion. The second VT / VF detection criterion may require that the sensed cardiac electrical signal does not meet any VT / VF rejection rules.

[0114] The detection delay criteria applied at box 154 may include a first delay criterion and a second delay criterion that must be met for the control circuit 80 to delay VT / VF detection and the initiation of anti-tachyarrhythmia therapy. The first delay criterion may involve detecting evidence of oversensing and / or supraventricular rhythm based on analysis of cardiac electrical signals sensed by the sensing circuit 86. As further described below in conjunction with the accompanying flowchart, the control circuit 80 may be configured to update the state of the oversensing criterion and / or supraventricular rhythm criterion to satisfied or unsatisfied upon receiving a Vsense signal from the sensing circuit 86. The control circuit 80 may determine how the oversensing criterion and / or supraventricular rhythm criterion are consistently satisfied over a time interval or a specified number of Vsense signals.

[0115] In some examples, oversensing criteria may include multiple sets of criteria for detecting different types of oversensing that may occur. For example, as further described below, control circuitry 80 may be configured to update the state of one or more sets of non-cardiac noise oversensing criteria, for example, each time a Vsense signal is received from sensing circuitry 86. Control circuitry 80 may additionally or alternatively be configured to update the state of one or more sets of cardiac event oversensing criteria, for example, each time a Vsense signal is received from sensing circuitry 86. Additionally or alternatively, control circuitry 80 may be configured to update the state of one or more sets of supraventricular rhythm criteria. When it is determined that each of at least X of the most recent Y Vsense signals satisfies the state of any of the updated noise oversensing criteria and / or supraventricular rhythm criteria, control circuitry 80 may determine a first delay criterion that satisfies the detection delay criterion at block 154.

[0116] The detection delay criterion applied at box 154 may include a second delay criterion that requires determining that fewer than a threshold number or percentage of sensed signal waveforms (each sensed signal waveform corresponding to a single individual Vsense signal received from sensing circuit 86) have a VT / VF beat pattern. The second delay criterion can be applied to detect evidence of a genuine VT / VF signal waveform that makes it necessary to detect VT / VF without delay. Therefore, the detection delay criterion is met when fewer than a threshold number of recently sensed ventricular event signal waveforms are determined to each have a VT / VF beat pattern (e.g., characteristics indicating a sinusoidal fibrillation waveform). When a threshold number of recently sensed ventricular event signal waveforms are determined to each have a VT / VF beat pattern, it may be a genuine VT / VF rhythm and the detection delay criterion is not met.

[0117] When the detection delay criterion is not met at block 154, control circuit 80 may transition to block 156. Control circuit 80 may detect VT / VF and initiate treatment delivery, for example, scheduling ATP therapy and / or initiating charging of the high-voltage capacitor of treatment delivery circuit 84 in preparation for CV / DF shock delivery. Progressing to block 156 of flowchart 150 may correspond to transitioning to… Figure 5 The charging state 3 is shown in box 106.

[0118] Referring again to block 154, when control circuitry 80 determines that the detection delay criterion is met, control circuitry 80 may delay VT / VF detection even if the first VT / VF detection criterion is met at block 152. Control circuitry 80 can delay VT / VF detection by initiating a detection delay interval (also referred to herein as the "delay interval") at block 158. The detection delay interval can be 2 to 30 seconds, 3 to 9 seconds, and in one example, 5 seconds. In other examples, control circuitry 80 can delay VT / VF detection by waiting to receive a specified number of Vsense signals from sensing circuitry 86 (e.g., from a selected sensing channel of sensing channels 83 or 85).

[0119] Oversensitivity and / or non-sustained conducted supraventricular rhythms can be intermittent, or may temporarily disappear or subside, such that the first VT / VF detection criteria may become unmet during the detection delay if they are met at box 152 due to oversensitivity or a rapid supraventricular rhythm. CV / DF shock delivery can be avoided by delaying VT / VF detection when the first VT / VF detection criteria are met to effectively delay treatment initiation. Oversensitivity of SVT or ST that results in the meeting of the first VT / VF detection criteria due to cardiac or non-cardiac noise signals or conducted signals may disappear, causing the first VT / VF detection criteria to become unmet, and VT / VF detection may not be performed. Some examples of oversensing that may lead to NID satisfaction in the presence or absence of VT / VF include cardiac oversensing (e.g., wide QRS double counting, PWOS, or TWOS), non-cardiac oversensing (e.g., oversensing of EMI, skeletal muscle noise caused by myoelectric effects, or other environmental or lead-related noise), and oversensing caused by small R waves with high signal variability (e.g., due to changes in patient position, respiration, etc.). Low-amplitude R waves can be associated with both cardiac and non-cardiac oversensing because an automatically adjusted R-wave sensing threshold amplitude set based on the peak amplitude of low-amplitude R waves may lead to oversensing of relatively small-amplitude P waves, T waves, and / or non-cardiac noise. Any type of oversensing may result in NID satisfaction at box 152 as the first VT / VF detection criterion.

[0120] Therefore, when the detection delay criterion is met due to persistent evidence of oversensitivity associated with a Vsense signal received at the RRI meeting the NID, the control circuit 80 can proceed to block 158 and initiate the detection delay, for example, by starting a timer or counter, timing in units of time intervals or the number of Vsense signals until the end of a specified detection delay interval. As an example, the detection delay interval can be a specified time interval set to 2 to 10 seconds or 5 to 6 seconds, or it can be defined as the number of Vsense signals, such as 5 to 30 Vsense signals. Clinicians can program the detection delay interval to correspond to the time interval considered appropriate for delaying CV / DF shocks when a true VT / VF episode is present at the time the detection delay criterion is met.

[0121] After initiating the detection delay at block 158, control circuitry 80 can determine and (in memory 82) store the data required to determine whether the detection delay criteria are met after the delay expires. For example, when each Vsense signal is received from the selected sensing channel 83 or sensing channel 85 during the detection delay, control circuitry 80 can determine the state of one or more sets of oversensing criteria and / or one or more sets of supraventricular rhythm criteria at block 160 and buffer this state in memory 82. For each of the most recent Y Vsense signals, control circuitry 80 can buffer the state of each of the one or more sets of oversensing criteria and / or supraventricular rhythm criteria in memory 82. The states of each set of oversensing and / or supraventricular rhythm criteria can be buffered in memory 82 for each Vsense signal so that control circuitry 80 can determine whether the first delay criterion is met when the detection delay expires. However, in some examples, the control circuit 80 may not analyze the buffer state of the oversensing criterion and supraventricular rhythm criterion on each Vsense signal until the detection delay expires, as determined at box 162.

[0122] Additionally or alternatively, at block 160, control circuitry 80 may determine and store data for determining whether a second delay criterion is met by performing pulsation pattern analysis to determine when a sensed signal waveform (e.g., corresponding to exactly one Vsense signal from selected sensing channels 83 or 85) is or is not a VT / VF pulsation pattern. Pulsation pattern analysis may be performed by determining amplitude and / or signal width metrics, for example, to identify sensed signal waveforms as either non-VT / VF or VT / VF pulsation patterns. The following is in conjunction with... Figure 11 An example method is described for classifying sensed signal waveforms into non-VT / VF pulsation patterns or VT / VF pulsation patterns based on pulsation pattern analysis.

[0123] If the detection delay has not yet expired (the "No" branch of block 162), the control circuit 80 may update the VTI / VFI counter in response to the next Vsense signal received from the sensing circuit 86, and store the state of each of one or more oversensing criteria, supraventricular rhythm criteria, and / or pulsatility classifications, as determined at block 160 for the current Vsense signal. For example, for each of the most recent 8 to 20 Vsense signals, the states of the first delay criterion and the second delay criterion may be buffered in memory 82.

[0124] When the detection delay expires (the "Yes" branch of block 162), control circuitry 80 can determine at block 164 whether the maximum detection delay time has been reached. In some examples, VT / VF detection can only be delayed up to a specified maximum delay time. Therefore, control circuitry 80 can initiate the maximum delay time in response to the first satisfaction of the detection delay criterion, for example, by initiating a timer or counter set to count down the maximum delay time. As an example, the maximum delay time can be 5 to 60 seconds, 10 to 40 seconds, or 20 to 30 seconds. In an exemplary example, when the delay interval is set to five seconds at block 158, the maximum delay time can be 30 seconds, meaning that VT / VF detection may be delayed by five seconds each time the detection delay criterion is satisfied, up to six times. In another example, when the delay interval is initially set to five seconds at block 158, after the initial delay interval expires, control circuitry 80 can bob along (e.g., on each Vsense signal) to re-determine whether the detection delay criterion has been satisfied for another 25 seconds, thus bringing the maximum delay time to 30 seconds. The maximum delay time can be set to a specified time interval, a specified number of Vsense signals, or a combination of both (e.g., whichever arrives first). In other examples, the maximum delay time is optional and may not be used, allowing the total time for VT / VF detection to be delayed to be unlimited. The detection delay may end when a VT / VF is detected (due to the detection delay criterion not being met and all VT / VF detection criteria being met) or when the termination criterion is met.

[0125] If the maximum delay time is reached at box 164 (e.g., the maximum delay time expires) (and at least the first VT / VF detection criteria are still met), control circuitry 80 may proceed to box 156 to initiate anti-tachyarrhythmic therapy delivery, for example, by activating ATP and / or charging a high-voltage capacitor. (Based on the above...) Figure 5 In any of the examples described, control circuitry 80 may continue to monitor and analyze the sensed cardiac electrical signals to detect conditions for termination or discontinuation of treatment.

[0126] If the maximum delay time has not been reached at block 164, control circuitry 80 can re-determine at block 166 whether the detection delay criterion is still met. If the detection delay criterion is no longer met, based on the data buffered in memory 82 (at block 160), control circuitry 80 can detect VT / VF and proceed to block 156 to initiate treatment delivery. Although Figure 6 Although not explicitly shown, it should be understood that in order to proceed to box 156 to detect VT / VF and initiate treatment delivery, control circuit 80 can verify that the first VT / VF detection criterion is still met even if the detection delay criterion at box 166 becomes unmet after the delay expires.

[0127] If the detection delay criterion is met based on the data buffered in memory 82, control circuitry 80 may continue delaying VT / VF detection at block 168. In some examples, control circuitry 80 may continue delaying detection by restarting the same delay interval (defined as a time interval in seconds or the number of Vsense signals) initiated at block 158. In other examples, control circuitry 80 may continue delaying detection by restarting a delay different from the delay initiated at block 158 (e.g., a different time interval or a different number of Vsense signals). For example, when continuing delay detection at block 168, a shorter delay interval or fewer Vsense signals may be counted down. In some examples, delay detection is continued on a beat-by-beat basis such that when the detection delay criterion is met again after the initial detection delay at block 162 has expired, detection is delayed by only one Vsense signal.

[0128] Control circuit 80 can verify that the first VT / VF detection criterion is still met (block 170). If not, control circuit 80 can wait at block 152 for the first VT / VF detection criterion to be met again. In some cases, if the NID and / or termination criteria are no longer met, control circuit 80 can transition back to the unrelated sensing state 1, as described above. Figure 5 As described.

[0129] If the first VT / VF detection criterion is still met at box 170, control circuit 80 may buffer the data required to re-determine whether the detection delay criterion is still met at box 160. After the continuous detection delay expires (which may be after the next single Vsense signal is received), control circuit 80 may re-determine whether the detection delay criterion is still met at box 166 (if the maximum delay time has not yet expired). Control circuit 80 may continue to determine whether the detection delay criterion is met at box 166 on a beat-by-beat or less frequent basis until the maximum detection delay time expires (the "yes" branch of box 164), the detection delay criterion becomes unmet (the "no" branch of box 166), or the termination criterion becomes met (causing the transition back to the previous state). Figure 5(Irrelevant state 1) is shown, with the first one arriving as the standard.

[0130] Figure 7 This is a flowchart 200 of a rapid arrhythmia detection method that can be performed by a medical device, according to another example. At block 202, control circuitry 80 may determine whether a first rapid arrhythmia detection criterion is met based on at least one cardiac electrical signal received by sensing circuitry 86. The first rapid arrhythmia detection criterion met at block 202 may correspond to the Vsense signal received from selected sensing channels 83 or 85 meeting NID, or in combination with the above. Figure 6 The description or combination Figure 5 The described first rapid arrhythmia detection criteria are any examples of the transition between irrelevant state 1 and relevant state 2. In response to the first rapid arrhythmia detection criteria being met at block 202, control circuitry 80 can... Figure 5 The irrelevant state 1 is transformed into the relevant state 2.

[0131] At block 204, control circuitry 80 can determine whether a second VT / VF detection criterion is met. In the example shown, control circuitry 80 can determine that the second VT / VF detection criterion is met by determining at block 204 that any one of one or more rejection rules is not met. Control circuitry 80 can apply one or more rejection rules that, when met, cause control circuitry 80 to suspend VT / VF detection when the first VT / VF detection criterion is met. Each rejection rule may include criteria applied to one or more cardiac electrical signals sensed by sensing circuitry 86 to detect evidence of oversensing or supraventricular rhythm (e.g., SVT or ST). Each rejection rule may include criteria for detecting, for example, evidence of oversensing of non-cardiac noise, evidence of oversensing of cardiac events (e.g., PWOS or TWOS), or evidence of supraventricular rhythm. The first VT / VF detection criterion met at block 202 may be met when the cardiac electrical signals sensed by sensing circuitry 86 are disturbed by non-cardiac noise, when cardiac oversensing occurs, or when SVT or ST is in progress and being conducted to the ventricles. In this example, control circuit 80 may apply one or more rejection rules, which, when satisfied, cause control circuit 80 to pause VT / VF detection by waiting for the next Vsense signal at block 205.

[0132] When the next Vsense signal is received at block 205, control circuit 80 can update the VTI / VFI counter and re-determine the state of the rejection rule. If the first VT / VF detection criterion is no longer met at block 206, for example, if NID is no longer met, control circuit 80 can wait at block 202 for the first VT / VF detection criterion to be met again before continuing with the process in flowchart 200. Based on the above... Figure 5 The description should be understood to mean that in some cases, if the termination criterion is met while the control circuit 80 is waiting for the second VT / VF detection criterion to be met, the control circuit 80 may switch to an unrelated sensing state 1.

[0133] Examples of VT / VF rejection rules that can be applied at box 204 include, but are not limited to, SVT rejection rules, atrial fibrillation rejection rules, PWOS rejection rules, TWOS rejection rules, EMI rejection rules, and electromyographic noise rejection rules. Examples of VT / VF rejection rules and methods for determining when a VT / VF rejection rule is met are described in the references incorporated below. Each individual rejection rule may include criteria similar to the detection delay criterion, as each individual rejection rule may include a first criterion for detecting evidence of a given type of oversensing (e.g., evidence of a type of non-cardiac noise such as EMI or electromyographic, evidence of a type of cardiac event oversensing such as PWOS or TWOS) or evidence of supraventricular rhythm. In some cases, a rejection rule may include a combination of a first criterion and a second criterion requiring that the number of VT / VF morphological beats in the most recently received Vsense signal be less than a threshold number. However, some VT / VF rejection rules may not necessarily include criteria associated with a limited number of VT / VF morphological beats in the Vsense signal set being evaluated.

[0134] Satisfying the VT / VF rejection rule on a given Vsense signal means that the control circuit 80 has determined, based on analysis of one or more cardiac electrical signals sensed by the sensing circuit on a specified number of Vsense signals, that a first criterion associated with a type of oversensitivity or supraventricular rhythm is met. The given rejection rule may analyze various characteristics of the RRI determined between consecutively received Vsense signals and / or the pulsating signal segments buffered for each corresponding Vsense signal. To satisfy at least some of the rejection rules, the control circuit 80 may also determine that a number of Vsense signals less than a threshold are identified as VT / VF morphological beats within the specified number of Vsense signals. Satisfying the rejection rule on a single Vsense signal (based on analysis of a specified number of Vsense signals) may cause the control circuit 80 to suspend VT / VF detection until the next Vsense signal.

[0135] However, the detection delay criterion is satisfied when multiple sets of a specified number of Vsense signals meet any combination of the criteria for oversensitivity and / or supraventricular rhythm. The detection delay criterion may require multiple (e.g., consecutive) sets of Vsense signals to continuously meet the criteria for oversensitivity and / or supraventricular rhythm, and when met, may delay VT / VF detection by a specified time interval or multiple Vsense signals. Each rejection rule is satisfied when a set of Vsense signals meets the criteria associated with one type of oversensitivity or one type of supraventricular rhythm, while the detection delay criterion is satisfied when, for example, at least X sets of Y sets of Vsense signals continuously meet any combination of criteria associated with multiple different types of oversensitivity and / or supraventricular rhythm.

[0136] When the first VT / VF detection criterion is met at block 202 and no rejection rule is met (the "No" branch of block 204), control circuit 80 can determine that both the first and second VT / VF detection criteria are met. Control circuit 80 can then proceed to block 210. At block 210, control circuit 80 can determine whether a delay interval has been previously initiated since the first VT / VF detection criterion was met at block 202. When the detection delay criterion is met at block 212, control circuit 80 can initiate a delay interval at block 216. If a delay interval has been initiated, control circuit 80 can proceed to block 218. If the delay interval is not currently running when both the first VT / VF detection criterion (e.g., NID) and the second VT / VF detection criterion (e.g., no rejection rule) are met, control circuit 80 can proceed to block 212 to determine whether the detection delay criterion is met.

[0137] At block 212, control circuitry 80 applies a detection delay criterion to one or more sensed cardiac signals to determine whether to detect VT / VF or delay VT / VF detection. The detection delay criterion can be applied when the first VT / VF detection criterion is met and no rejection rule is met, because control circuitry 80 will pause VT / VF detection until at least the next Vsense signal is met (and then the rejection rule can be re-evaluated). Therefore, in some examples, control circuitry 80 may not apply the detection delay criterion until no rejection rule is met, but the first VT / VF detection criterion is (still) met, such as NID.

[0138] In some examples, the detection delay criterion applied at block 212 may require that at least one VT / VF rejection rule be met on each of at least a threshold number or percentage of a specified number of recent Vsense signals. For example, if any one or more VT / VF rejection rules are met on at least 50% of the recent Vsense signals (e.g., at least 6 out of 12) (but not on the current Vsense signal, thus triggering an evaluation of the detection delay data), the control circuitry 80 may determine at block 212 that the detection delay criterion is met.

[0139] In some examples, control circuitry 80 may apply one or more SVT rejection rules and / or one or more oversensing rejection rules. In some examples, when no VT / VF rejection rule is satisfied on the Y-th Vsense signal, control circuitry 80 may evaluate the status of oversensing rejection rules (but not necessarily SVT rejection rules) for the most recent Y Vsense signals. For example, if at least one oversensing rejection rule is satisfied on at least X of the Y Vsense signals, control circuitry 80 may determine at block 212 that the detection delay criterion is met. The VT / VF rejection rules satisfied on each of the at least X of the most recent Y Vsense signals do not necessarily have to be the same rejection rule. For example, an EMG noise rejection rule may be satisfied on a portion of the X Vsense signals, and a PWOS rejection rule, a TWOS rejection rule, and / or an EMI rejection rule may be satisfied in any combination of the other portions of the X Vsense signals. Any combination of the selected VT / VF rejection rules can be satisfied on X Vsense signals to meet the detection delay criteria, but it should be remembered that when the VT / VF rejection rule is satisfied "on Vsense signals", the analysis of the cardiac electrical signals sensed on a set of the most recent Vsense signals has been performed to determine whether the rejection rule is satisfied.

[0140] In other examples, as described above, detection delay criteria may include a first delay criterion related to the detection of evidence of oversensitivity and / or supraventricular rhythms. The following section combines... Figures 8 to 10A first delay criterion that can be applied at block 212 is generally described. Control circuit 80 can apply a second delay criterion to verify the detection of VT / VF beat morphology on less than a threshold number of recent Vsense signals. The detection delay criterion is met when the first delay criterion (associated with evidence of oversensing and / or supraventricular rhythm) is satisfied and less than a threshold number of recently sensed ventricular event signal waveforms are determined to have VT / VF beat morphology. When more than a threshold number of recently sensed ventricular event signal waveforms are determined to have VT / VF beat morphology, a true VT / VF rhythm may be present. A true VT / VF rhythm may occur in the presence of oversensing and / or SVT or ST. Control circuit 80 can transition to block 214 in response to failure to meet the detection delay criterion. Control circuit 80 can detect VT / VF and initiate treatment delivery, e.g., scheduling ATP therapy and / or initiating charging of the high-voltage capacitor of treatment delivery circuit 84 to prepare for CV / DF shock delivery. Proceeding to block 214 of flowchart 200 may correspond to the transition to... Figure 5 The charging state 3 is shown in box 106.

[0141] Combined with the following text Figure 8 As further described, if it is determined that at least one set of oversensing criteria or supraventricular rhythm criteria are met on each of at least X Vsense signals out of the most recent Y Vsense signals, and not necessarily on the current or most recently received Vsense signal, then control circuitry 80 may determine at block 212 that a detection delay criterion is met. In various examples, the set of oversensing criteria and / or supraventricular rhythm criteria met on each of X Vsense signals out of the most recent Y Vsense signals may or may not be the same set of criteria. When no rejection rule is met on the current Vsense signal (the "No" branch of block 204), control circuitry 80 may detect VT / VF unless a detection delay criterion is met, i.e., evidence of persistent oversensing and / or persistent supraventricular rhythm prior to the current Vsense signal (e.g., during the most recent Y Vsense signals), and few or no beats are identified as having a VT / VF beat pattern.

[0142] Therefore, when the detection delay criterion is met, the control circuit 80 can proceed to block 216 and initiate the detection delay interval, for example, by starting a timer or counter to count until a specified time interval or the end of the Vsense signal count. As an example, the delay interval can be between 2 and 30 seconds, and in some examples, it can be 5 seconds. (As mentioned above...) Figure 6As described, in other examples, the detection delay interval can be defined as the number of Vsense signals. Clinicians can program the detection delay interval to a specified time interval or number of Vsense signals deemed appropriate for delaying CV / DF shocks when a true VT / VF episode is present and the detection delay criteria are met.

[0143] After initiating the delay interval, control circuit 80 may determine and (in memory 82) store the data required to determine whether the detection delay criteria are met. For example, when each Vsense signal is received from a selected sensing channel 83 or sensing channel 85 of sensing circuit 86 during the delay interval, control circuit 80 may determine the state of one or more sets of oversensing criteria and / or one or more sets of supraventricular rhythm criteria at block 218 and buffer that state in memory 82. Control circuit 80 may buffer the state of each of one or more sets of oversensing criteria and / or supraventricular rhythm criteria of the most recent Y Vsense signals in memory 82. However, in some examples, control circuit 80 may not analyze the buffered data until the delay interval expires, as determined at block 220.

[0144] As described above, control circuit 80 can determine and store data for determining whether a second delay criterion is met by performing pulsatility analysis on the sensed signal waveform (e.g., a signal waveform buffered in response to receiving exactly one Vsense signal from selected sensing channels 83 or 85). Each Vsense signal received from selected sensing channels 83 or 86 can trigger control circuit 80 to store a pulsatility signal segment in memory 82 after the VTI / VFI counter has started incrementing (e.g., reaching a threshold of 2, 3, 6, or other thresholds less than NID). Pulsatility analysis can be performed by determining at least one of an amplitude measure, a signal width metric, an overall waveform morphology matching score, and / or other morphology metrics used to identify pulsatility signal segments containing the time of triggering the Vsense signal as either non-VT / VF pulsatility or VT / VF pulsatility. The following is in conjunction with... Figure 11 An example method is described for classifying sensed signal waveforms into non-VT / VF pulsation patterns or VT / VF pulsation patterns. (See below for details.) Figure 8 As described, the control circuit 80 can determine the data used to determine whether the detection delay criterion is met by determining the state of at least one oversensing criterion and updating the buffer (box 218) that stores the state and the morphology-based pulsation classification of each Vsense signal received from the selected sensing channel 83 or 85.

[0145] If the delay interval has not yet expired (No branch of block 220), the control circuit 80 may update the VTI / VFI counter in response to each Vsense signal received from the sensing circuit 86, and update the detection delay criterion data in the memory 82, as determined at block 218 for the current Vsense signal. When the detection delay interval expires (Yes branch of block 220), if the maximum detection delay time has not been reached, as determined at block 222, the control circuit 80 may determine at block 224 whether the detection delay criterion is still met.

[0146] In some examples, VT / VF can only be delayed for a maximum specified delay time. As an example, the maximum delay time can be 5 to 60 seconds, 10 to 40 seconds, or 20 to 30 seconds. In an illustrative example, when the delay interval is set to five seconds at box 216, the maximum delay time can be 30 seconds. In some examples, VT / VF detection may be delayed by five seconds each time a detection delay criterion is met, up to a maximum of six times. In other examples, after the initial delay interval expires, control circuitry 80 may evaluate a first VT / VF detection criterion (e.g., NID), a second VT / VF detection criterion (e.g., rejection rule), and a detection delay criterion (if no rejection rule is met) on a beat-by-beat basis (e.g., on each Vsense signal received from the selected sensing channel 83 or 85). If the maximum delay time is reached at box 222 (and at least the first VT / VF detection criterion is still met), control circuitry 80 may proceed to box 214 to initiate anti-tachyarrhythmia treatment delivery. In some examples, if the maximum delay time is reached, the control circuit 80 can verify that the NID has been achieved and that no rejection rule is met. When these three conditions are met, the control circuit 80 can detect VT / VF and control the treatment delivery circuit 84 to initiate anti-tachyarrhythmia treatment.

[0147] If the maximum delay time has not been reached at block 222, control circuit 80 can re-determine at block 224 whether the detection delay criterion is still met. If the detection delay criterion is no longer met, based on the data buffered in memory 82 (at block 218), control circuit 80 can detect VT / VF and proceed to block 214 to initiate treatment delivery. Although Figure 7 While not explicitly shown, it should be understood that in order to proceed to box 214 to detect VT / VF and initiate treatment delivery, it may be necessary to still meet at least the first VT / VF detection criterion if the detection delay criterion at box 224 becomes unmet. In some examples, control circuitry 80 proceeds to box 214 to initiate treatment delivery when the detection delay criterion is not met, no rejection rule is met on the current Vsense signal, and NID is satisfied.

[0148] If the detection delay criterion is met based on the data buffered in memory 82, control circuitry 80 may return to box 205 to wait for the next Vsense signal, determine whether the first VT / VF detection criterion is still met (box 206) based on the next Vsense signal, and proceed to box 218 to buffer the delay criterion data determined for the next Vsense signal if no rejection rule is met. In some examples, if the detection delay criterion is met again at box 224, control circuitry 80 may restart the delay interval. In other examples, control circuitry 80 may initiate a delay interval that is shorter or longer than the delay interval initially initiated at box 216. In other examples, the specified delay interval is not restarted (but the maximum delay time may be running), and control circuitry 80 evaluates the detection delay criterion for each received Vsense signal to determine whether to continue delaying VT / VF detection or proceed to box 214 to initiate treatment delivery, for example, by initiating ATP and / or high-voltage capacitor charging.

[0149] Figure 8 This is a flowchart 250 of a method for determining when a detection delay criterion is met, for example, in Figure 6 At box 154 or box 166 or at Figure 7 At box 212 or box 224. At box 252, control circuitry 80 may determine whether a first delay criterion has been met on at least a threshold number of X beats (e.g., X Vsense signals) out of the most recent Y beats (e.g., Y Vsense signals). In some examples, the first delay criterion involves detecting evidence of oversensing. Oversensing may involve oversensing of cardiac events, such as PWOS or TWOS that result in erroneous Vsense signals. Erroneous Vsense signals may cause erroneous RRIs to be counted as VTI / VFI. In some cases, when PWOS and / or TWOS occur, the erroneous RRI may actually be PRI, RPI, RTI, and / or TRI.

[0150] Additionally or alternatively, the first delay criterion applied at box 252 may include a criterion related to the oversensing of non-cardiac noise. Skeletal muscle electromyographic signal pulses or other non-cardiac electrophysiological signals or electromagnetic interference (EMI) pulses may be present in the cardiac electrical signals sensed by sensing channel 83 or sensing channel 85. Non-cardiac noise signals may be incorrectly sensed as R waves, resulting in erroneous Vsense signals and achieving NID based on erroneous RRI.

[0151] In some examples, the first delay criterion applied at box 252 may include criteria related to the detection of supraventricular rhythms. The Vsense signal may correspond to a real R wave that conducts rapidly from the atrium during SVT or ST. Even if NID is achieved, the detection of VT / VF and the delivery of ventricular antitachyarrhythmic therapy may be delayed when evidence of a supraventricular rhythm is detected.

[0152] The following text combines Figure 9 and Figure 10 Various combinations of oversensing and / or supraventricular rhythm criteria that can be satisfied up to a first delay criterion of the detection delay criterion are described. In some examples, one or more sets of oversensing criterion states (e.g., satisfied or not satisfied) may be buffered in memory 82 for each of the most recent Y Vsense signals. Additionally or alternatively, one or more sets of supraventricular rhythm criteria states may be buffered in memory 82 for each of the most recent Y Vsense signals. In some cases, [the following can be done] Figure 7 At box 204, multiple rejection rules related to oversensing (e.g., PWOS, TWOS, and non-cardiac noise oversensing) and supraventricular rhythms are applied to determine whether a second VT / VF detection criterion is met if a first VT / VF detection criterion is met. However, the first delay criterion for the detection delay criterion may be designed to detect evidence of selected types of oversensing and / or supraventricular rhythms, and may be a subset of the types of oversensing and / or supraventricular rhythms detected when the rejection rules are met. For example, the first delay criterion may be designed to detect evidence of different types of oversensing, such as including cardiac event oversensing (PWOS and / or TWOS) and non-cardiac noise oversensing, without detecting different types of supraventricular rhythms that can be handled by the rejection rules.

[0153] Oversensing can be more intermittent and transient than supraventricular rhythms. The rejection rules associated with supraventricular rhythms can always be satisfied on each Vsense signal, preventing control circuitry 80 from detecting VT / VF. However, oversensing can be intermittent, making it possible that the rejection rules associated with oversensing may not be satisfied on a single Vsense signal. This could lead to erroneous VT / VF detection in the presence of intermittent noise or oversensing of cardiac events when the oversensing rejection rules are not met. VT / VF detection can be delayed by applying a detection delay criterion that determines when evidence of oversensing is consistently detected, for example, detected on at least X beats out of Y beats, even if not detected on the current Vsense signal. Therefore, in some examples, the first delay criterion may only involve one or more types of oversensing and does not include supraventricular rhythm criteria.

[0154] The criteria satisfied at at least X of the Y beats in box 252 may not need to be associated with the same type of oversensing or the same type of supraventricular rhythm (when included) in each of the X beats. For example, a cardiac event oversensing criterion (e.g., PWOS criterion or TWOS criterion) may be satisfied at one or more of the X beats, a non-cardiac noise criterion (e.g., electromyographic noise criterion or EMI criterion) may be satisfied at one or more of the X beats, and / or an SVT criterion may be satisfied at one or more of the X beats. When at least one set of criteria associated with oversensing and / or supraventricular rhythm is not satisfied at each of the at least X Vsense signals in the most recent Y Vsense signals, the control circuit 80 may determine at box 256 (the "No" branch of box 252) that the detection delay criterion is not met. If at least one set of criteria (in any combination) of multiple sets of criteria related to oversensitivity and / or supraventricular rhythms is met on at least X of the Y Vsense signals, the control circuit 80 may determine at block 258 that the detection delay criterion is met. However, the detection delay criterion may additionally require the detection of VT / VF pulsation patterns in fewer than a threshold number of the most recent Vsense signals, as indicated at block 254.

[0155] At box 254, control circuit 80 can determine whether the morphological analysis of the pulsation signal segment corresponding to a given Vsense signal meets the VT / VF pulsation morphology criteria of the most recent Vsense signal with a threshold number. The following section combines... Figure 11 An example method for determining when a VT / VF pulsation pattern is detected is described. When control circuitry 80 detects a VT / VF pulsation pattern in each of at least M of the most recent N Vsense signals (the "Yes" branch of box 254), control circuitry 80 may determine at box 256 that a detection delay criterion is not met. Even if a first delay criterion is met, indicating evidence of persistent oversensing and / or supraventricular rhythm on the most recent Y Vsense signals, control circuitry 80 may not delay VT / VF detection if the waveform morphology of the individually sensed signal corresponding to a threshold number of Vsense signals meets the VT / VF pulsation pattern criterion. A VT / VF pulsation pattern detected for at least M of the N Vsense signals may indicate strong evidence of a Vsense signal corresponding to an R wave or fibrillation wave during a true VT / VF episode.

[0156] X criteria out of Y criteria used to determine the persistence of a first delay criterion, and M criteria out of N criteria used to detect evidence of VT / VF morphology of a separate waveform sensed as an R wave, may be applied to the same number of recent Vsense signals, e.g., Y equals N. Control circuitry 80 may buffer the state of one or more sets of criteria associated with oversensitivity and / or supraventricular rhythm, as well as the individual beat morphology (i.e., VT / VF or non-VT / VF beat morphology) of each of the recent Y Vsense signals (e.g., four to twenty, six to fourteen, or eight to twelve Vsense signals in various examples). In various examples, the threshold X applied to the number of Vsense signals satisfying at least one set of criteria associated with oversensitivity and / or supraventricular rhythm may correspond to 25% to 75%, 40% to 60%, or 50% to 55% of the Y Vsense signals. In various examples, the threshold M applied to the number of Vsense signals for which VT / VF pulsation patterns are detected can be 25% to 75%, 30% to 60%, or 50% of N pulsations. In an illustrative example, control circuitry 80 may determine at block 258 that the detection delay criterion is met when at least one set of criteria for a first delay criterion is met on more than 50% of the Y Vsense signals and less than 50% of the associated individually sensed signal waveforms are determined to have VT / VF pulsation patterns. For example, when Y and N equal 12, control circuitry 80 may determine at block 258 that the detection delay criterion is met when at least one set of oversensing criteria or supraventricular rhythm criteria is met on each of at least 7 of the most recent 12 Vsense signals and VT / VF pulsation patterns are detected on no more than 5 of the most recent 12 Vsense signals.

[0157] As described above, control circuit 80 can delay VT / VF detection by initiating a delay interval in response to meeting the detection delay criterion. When the delay interval expires and the detection delay criterion is still met, VT / VF detection can be delayed up to a maximum delay time until the detection delay criterion is no longer met (and VT / VF detection is performed) or until the termination criterion is met, whichever occurs first, as described above. Figure 5 , Figure 6 and Figure 7 A general description.

[0158] Figure 9This is a flowchart 300 illustrating a method for determining when a detection delay criterion is met, based on some examples. Control circuitry 80 can be configured to begin updating the state of one or more sets of criteria for the first delay criterion when the VTI / VFI count has reached at least a threshold number. For example, morphological sensing channel 87 can be enabled when the VTI / VFI count has reached at least 1, 2, 3, 5, 8, or other threshold numbers. Figure 4 A morphological signal segment is provided to the control circuit 80 to perform morphological analysis. In response to receiving a Vsense signal from sensing channel 83 or 85, the control circuit 80 may acquire and analyze a pulsation signal segment from the morphological sensing channel 87. Morphological analysis may include determining one or more features of the pulsation signal segment and / or determining a morphological match score between the pulsation signal segment and a normally conducted R-wave template. Morphological analysis may be used by the control circuit 80 to determine the status of various rejection rules when NID is met and / or to determine when the detection delay criterion is met.

[0159] exist Figure 9 In the example, when a Vsense signal is received at block 301, control circuitry 80 can determine at block 302 whether a non-cardiac noise criterion is met. A non-cardiac noise criterion can be met on the current Vsense signal when the most recent Vsense signal of a threshold number is identified as a noise impulse. A noise impulse can be detected when EMI is present in the sensed cardiac electrical signal and / or when skeletal muscle noise impulses are present in the sensed cardiac electrical signal. Control circuitry 80 can determine at block 302 whether the current Vsense signal is a noise impulse and update the non-cardiac noise criterion state.

[0160] For example, if it is determined that the cardiac electrical signal sensed by sensing circuit 86 is contaminated by EMI, the current Vsense signal can be identified as a noisy beat. In some examples, control circuit 80 can detect EMI by resetting the "silent timer" whenever the cardiac electrical signal exceeds a noise threshold amplitude before the silent timer expires. The silent timer may initially be activated in response to a Vsense signal or another threshold exceeding the cardiac electrical signal. The silent timer may be set from 5 ms to 50 ms, and in some examples is set to approximately 25 ms. If the cardiac signal does not exceed the noise threshold amplitude before the silent timer expires, the silent timer may time out, for example, becoming inactive. The Vsense signal can be identified as a noisy beat when the silent timer is active upon receiving the next Vsense signal (e.g., due to multiple resets between Vsense signals due to a noise threshold amplitude exceeding the silent timer before it expires). In some examples, the duration for which the silent timer is active upon receiving a Vsense signal is compared to a threshold used to detect the Vsense signal as a noisy beat. At block 302, control circuitry 80 can determine whether a threshold number of noise beats have been detected from a specified number of recent Vsense signals. For example, if at least 25%, 30%, 50%, or other specified percentage of a specified number of recent Vsense signals (e.g., 6 to 20 recent Vsense signals) are identified as noise beats, control circuitry 80 can determine at block 302 that the non-cardiac noise criterion status of the current Vsense signal is positive. Control circuitry 80 can set a noise criterion status flag to "1" in a buffer in memory 82 to count the number of Vsense signals that meet the non-cardiac noise criterion. Note that the current Vsense signal may or may not be a noise beat, but at least a threshold number of recent Vsense signals can be counted as noise beats so that the noise criterion status flag of the current Vsense signal is set to "1".

[0161] Additionally or alternatively, control circuitry 80 may be configured to determine at block 302 whether a myoelectric potential noise criterion is met. In response to a Vsense signal, control circuitry 80 may receive a pulsation signal segment from sensing circuitry 86 to analyze the presence of skeletal muscle myoelectric potential (or other non-cardiac) noise pulses. The pulsation signal segment may correspond to a single Vsense signal received from one of the selected sensing channels 83 or 85. Control circuitry 80 may identify noise pulses within the pulsation signal segment and count the number of noise pulses present. Noise pulses may be identified from the rectified pulsation signal segment, for example, based on the pulse peak amplitude and pulse width between zeros of the rectified signal segment. In some examples, control circuitry 80 may mark the Vsense signal as a noise pulsation when the number of noise pulses counted in the pulsation signal segment meets a noise pulsation threshold. When a threshold number of Vsense signals (e.g., 25%, 30%, 50%, or other percentages of a specified number of recent Vsense signals) are identified as noise beats based on noise pulse count, control circuitry 80 can determine that a non-cardiac noise criterion is met. Example methods for determining when a Vsense signal is a noise beat are generally disclosed in U.S. Patent No. 8,095,206 (filed May 1, 2007 by Ghanem et al.), U.S. Patent No. 10,470,681 (filed May 26, 2017 by Greenhut et al.), and U.S. Patent Application Publication No. 2023 / 0100431 (filed August 29, 2022) (which can be used in conjunction with the methods disclosed herein for determining when a detection delay criterion is met), the entire contents of all these patents are incorporated herein. These incorporated references provide examples of applying VT / VF rejection rules that can be used as a second VT / VF detection criterion in conjunction with the techniques disclosed herein.

[0162] It should be understood that control circuit 80 can be configured to employ multiple methods to detect non-cardiac noise contamination of the cardiac electrical signal sensed by sensing circuit 86. Control circuit 80 can determine at block 302 when a non-cardiac noise criterion is met based on one or more methods used for noise detection, and when the noise criterion is met, mark the current Vsense signal as having a positive noise criterion state. It should be noted that in some examples, if a sufficient number of previous Vsense signals are identified as noise impulses or meet other noise criteria when the current Vsense signal is received, the current Vsense signal may or may not be identified as a noise impulse when the noise criterion is determined to be met.

[0163] At block 306, control circuit 80 may apply criteria to cardiac electrical signal segments and / or Vsense signals received from sensing circuit 86 to determine the state of cardiac event oversensing criteria. Control circuit 80 may apply criteria for detecting PWOS and / or TWOS. When PWOS or TWOS is detected, the cardiac oversensing detection state of the corresponding Vsense signal may be marked as positive. The currently received Vsense signal may or may not be an oversensing signal; however, the criteria for detecting PWOS or TWOS may be met based on analysis of the most recent RRI determined between the received Vsense signal and / or the waveform characteristics of the sensed signal associated with the Vsense signal (e.g., as determined from the pulsating signal segment).

[0164] Example methods for detecting TWOS are generally disclosed in U.S. Patent No. 9,597,525 (filed May 6, 2015 by Cao et al.) and U.S. Patent No. 10,850,113 (filed July 20, 2017 by Cao et al.), which are adaptable for use in conjunction with the detection delay methods disclosed herein and / or for applying VT / VF rejection rules, the entire contents of which are incorporated herein. In various examples, control circuitry 80 may be configured to detect cardiac event oversensing based on alternating patterns of the RRI determined from the Vsense signal and / or alternating patterns of the peak amplitude, signal width, morphological matching score, and / or other features of the signal waveform associated with the Vsense signal received from sensing circuitry 86.

[0165] In one example, TWOS can be detected on the current Vsense signal when it is identified in at least a threshold number of recent Vsense signal sequences. Alternation pairs of Vsense signals can be identified based on alternation patterns of RRI, peak amplitude, peak slope, morphological match score, or other signal characteristics. Possible R waves and possible T waves can be identified from the alternation pairs. RT pairs can be identified in the series of Vsense signals when a possible R wave identified from an alternation pair is associated with a relatively high morphological match score (relative to a known R wave template that can be stored in memory 82) and a stable peak amplitude, and a possible T wave identified from an alternation pair is associated with a relatively low morphological match score. Subsequently, when a threshold number of RT pairs (and / or TR pairs) are identified from a series of recent Vsense signals and associated pulsation signal segments, it can be determined that the TWOS criterion is met on the current Vsense signal.

[0166] In another example, when control circuit 80 identifies a threshold number of T-waves in a series of recent Vsense signals based on event intervals and / or morphology and determines that the corrected RRI (based only on Vsense signals in the series not identified as T-waves) is greater than VTI / VFI, it can be determined that the TWOS criterion is met on the current Vsense signal. Control circuit 80 can identify T-waves in a series of Vsense signals based on comparative analysis of peak amplitude, morphology matching score, maximum slope, or other signal characteristics associated with the Vsense signal, without necessarily requiring repetitive, alternating patterns of R-waves and T-waves. In some cases, TWOS can be intermittent and variable, making continuous alternation patterns of R-waves and T-waves not necessarily detectable, nor a necessary condition for meeting the TWOS criterion on a given Vsense signal.

[0167] In another example, a cardiac event oversensing criterion can be determined at block 306 based on a PWOS criterion applied by control circuitry 80. Control circuitry 80 can determine that PWOS is detected in the current Vsense signal when a high-low-high or low-high-low pattern of peak amplitude, peak slope, or morphological matching score (compared to a known R-wave template) can be identified based on analysis of the currently sensed waveform and the first two sensed waveforms associated with three consecutive Vsense signals. When PWOS is detected on each of the most recent Vsense signals in a threshold number of times, control circuitry 80 can determine that the PWOS criterion is positive. U.S. Patent Application Publication No. 2021 / 0170170 (filed December 2, 2020 by Mischhler et al.) and U.S. Patent Application Publication No. 2023 / 0107061 (filed August 26, 2022 by Greenhut et al.) generally disclose examples of PWOS detection methods that can be used to determine the PWOS standard state at box 306 and / or to apply VT / VF rejection rules, the entire contents of which are incorporated herein by reference.

[0168] In some examples, PWOS is detected from a sequence of three consecutively sensed Vsense signals, based at least on the interpeak signal amplitude determined from three pulsating signal segments (e.g., pulsating signal segments received from morphological signal channel 87) associated with the three Vsense signals. The difference between the first two interpeak signal amplitudes and the difference between the last two interpeak signal amplitudes can be compared to detect a high-low-high or low-high-low pattern of the interpeak amplitudes, thereby satisfying the PWOS criterion. The interpeak signal amplitudes can be buffered pulsatially in memory 82 for use in determining when the PWOS criterion is met.

[0169] In some examples, control circuitry 80 may compare the interpeak signal amplitude buffered to determine the PWOS standard state with other environmental noise standards to determine other noise standard states. For example, control circuitry 80 may compare the interpeak amplitude with a noise threshold amplitude. An environmental noise standard may be met on the current Vsense signal when a threshold number of Vsense signals are associated with an interpeak amplitude smaller than the noise threshold amplitude. Control circuitry 80 may determine the noise threshold amplitude based on the maximum interpeak amplitude. In one example, an environmental noise oversensitivity standard may be met on the current Vsense signal when the average of two or more minimum interpeak amplitudes is less than a fraction (e.g., one-third, one-quarter, one-fifth, or one-sixth) of the maximum interpeak amplitude of a specified number of pulsating signal segments (e.g., 12 pulsating signal segments). The above-incorporated U.S. Patent No. 10,470,681 (Greenhut et al., filed May 26, 2017) generally discloses example methods for using interpeak amplitudes, which can be used to detect noise pulses up to the oversensing criterion of a first delay criterion.

[0170] It should be understood that the control circuit 80 can be configured to employ multiple methods to detect oversensing of cardiac signals by the sensing circuit 86. The control circuit 80 can determine the state of the cardiac signal oversensing criterion for the current Vsense signal at block 306 according to one or more methods used to detect cardiac signal oversensing. When the cardiac signal oversensing criterion is met, the current Vsense signal can be marked in memory 82 as having a positive cardiac signal oversensing criterion state. It should be noted that if a sufficient number of previous Vsense signals are identified as oversensing cardiac events when the current Vsense signal is received, the current Vsense signal may or may not be identified as an oversensing event, such as a P wave or T wave, when the cardiac signal oversensing criterion is determined to be met.

[0171] In some examples, control circuitry 80 may apply criteria to segments of cardiac electrical signals and / or Vsense signals received from sensing circuitry 86 to determine when a supraventricular rhythm (e.g., SVT or ST) is conducted to the ventricles. Control circuitry 80 may determine when supraventricular rhythm criteria are met (in [the context of the previous sentence]) upon receiving the current Vsense signal at block 308. Figure 9 This is referred to as the "SVT standard" in China.

[0172] Control circuit 80 can be configured to update the count of SVT beats detected from a specified number of recently received Vsense signals in response to receiving a Vsense signal, to determine SVT criteria at block 308. SVT beats can be detected based on a morphological match score between a beat signal segment associated with the Vsense signal and a previously established R-wave template, which can be stored in memory 82. The R-wave template can be established during a known sinus rhythm, for example, to provide a reference template for a ventricular QRS waveform conducted from the atrium. SVT beats can be detected based on a morphological match score exceeding a threshold. Additionally or alternatively, control circuit 80 can identify SVT beats based on maximum peak amplitude, signal width, peak polarity, the time interval from exceeding the R-wave sensing threshold to maximum peak amplitude, and / or other characteristics of the beat signal segment associated with the Vsense signal.

[0173] In some examples, when a threshold number of SVT beats are identified from a specified number of recent Vsense signals (e.g., at least 25%, at least 30%, or at least 50% or other specified percentage), control circuit 80 may determine that the SVT criterion is met on the current Vsense signal. Additionally or alternatively, control circuit 80 may determine that the SVT criterion is met based on meeting RRI stability, peak amplitude stability, or other stability criteria (indicating monomorphic rhythms).

[0174] In some examples, control circuit 80 may determine that SVT criteria are met upon detection of at least one long pause. Control circuit 80 may be configured to detect a long pause when the RRI is greater than a threshold interval, the previous RRI is VTI / VFI, and the morphology of the leading and / or ending signal waveforms of the long pause has a morphology matching score exceeding a threshold (relative to the R-wave template). In the presence of atrial fibrillation, atrial fibrillation waves may conduct to the ventricles at irregular rates, making a long RRI with leading and / or ending Vsense signals associated with a high morphology matching score relative to a reference R-wave template potentially evidence of conducted SVT.

[0175] It should be understood that control circuit 80 can be configured to detect evidence of SVT based on multiple criteria associated with RRI, the morphology of the sensed signal waveform, and / or one or more sensed signal waveform characteristics (e.g., peak amplitude, peak polarity, signal width, peak time over time relative to the R-wave sensing threshold, etc.). When the SVT criteria are met based on a specified number of Vsense signals being identified as SVT beats, the SVT criterion state of the current Vsense signal can be indicated as positive, for example, by moving a "1" into the detection delay data buffer in memory 82. The current Vsense signal may or may not be associated with an R-wave conducted from the atrium, but the SVT detection criteria can be met based on analysis of the most recently sensed Vsense signals. U.S. Patent No. 10,555,684 (filed February 11, 2020 by Zhang et al.) and U.S. Patent No. 11,116,981 (filed December 12, 2018 by Zhang et al.), the entire contents of which are incorporated herein by reference. These incorporated references also provide examples of SVT rejection rules and atrial fibrillation rejection rules that can be used in conjunction with the detection delay techniques disclosed herein as VT / VF rejection rules.

[0176] At block 314, when at least one of the non-cardiac noise criterion, the cardiac signal oversensitization criterion, or the SVT criterion is met on the current Vsense signal, the control circuit 80 may update the overall state indicating whether the first delay criterion is met. When updating the states of the non-cardiac noise criterion, the cardiac signal oversensitization criterion, and the SVT criterion at blocks 302, 304, and 306, the buffer in memory 82 may be updated with each Vsense signal, for example, as described below. Figure 11 As described below, these states can be ORed together such that the overall state of the first delay criterion on the current Vsense signal is positive when any of the criterion states updated at blocks 302, 306, and 308 is positive. As indicated above, when the first criterion state is positive for the number of thresholds X among the Y most recent Vsense signals, the control circuit 80 can determine that the detection delay criterion is met. For each Vsense signal with a positive state for a given noise (non-cardiac event) oversensing, cardiac event oversensing, or SVT criterion, at least a threshold number of the most recent Vsense signals are identified as noise beats, cardiac event oversensing beats, or SVT beats, respectively. Therefore, when the threshold number of Vsense signals is positive, multiple sets of Vsense signals have consistently met the corresponding oversensing or SVT criteria, thereby satisfying the first criterion of the detection delay criterion.

[0177] Figure 10 This is a flowchart 350 illustrating a method for determining the state of an oversensing criterion for delayed VT / VF detection, based on some examples. Figure 9 In the example, the first delay criterion for detecting delay is shown as including the SVT criterion. Figure 10 In some examples, the first criterion for delayed detection might require the oversensing criterion to be met, but might exclude criteria related to evidence of supraventricular rhythm. Oversensing (e.g., erroneous Vsense signals due to EMI, electromyography or other ambient noise, P waves and / or T waves) may be intermittent, and if VT / VF detection (and subsequent treatment) is delayed when NID is reached due to oversensing, the oversensing may subside before delivery of anti-tachyarrhythmic therapy. Therefore, in some examples, the criteria for delayed detection may include the oversensing criterion, but not necessarily the state of the SVT criteria to determine whether VT / VF detection should be delayed.

[0178] At block 351, control circuit 80 can receive a Vsense signal from sensing circuit 86. The process of flowchart 360 can be executed in response to a Vsense signal received before or after NID has been reached, because control circuit 80 can update the detection delay criterion buffer in memory 82 so that the detection delay data required to determine whether VT / VF detection should be delayed when NID (or other first VT / VF detection criteria) is met is available. For example, when the VTI / VFI counter reaches a threshold less than NID (e.g., 2, 3, 5, or other values), control circuit 80 can, according to… Figure 9 or Figure 10 The method begins to buffer the detection delay data so that when NID is reached, the detection delay data is available in memory 82.

[0179] In this example, control circuitry 80 can determine the state of one or more types of oversensing criteria. At block 352, control circuitry 80 can determine whether the myoelectric noise (sometimes called "muscle noise") criterion is met. (The above is combined with...) Figure 9The incorporated references describe examples of methods for determining whether a myoelectric noise criterion is met. If the myoelectric noise criterion is met at block 352, control circuitry 80 may determine at block 360 that the current Vsense signal meets the oversensing criterion. A first delay criterion may be flagged (e.g., set to 1) for the current Vsense signal in a detection delay data buffer in memory 82. When the first VT / VF detection criterion (and optionally a second VT / VF detection criterion, such as not meeting any rejection rule) is met, control circuitry 80 may count the current Vsense signal until the detection delay criterion is met. When the delay interval has expired (and the first VT / VF detection criterion is still met), control circuitry 80 may count the current Vsense signal until the detection delay criterion is met.

[0180] At box 354, control circuitry 80 determines whether the PWOS criterion is met. If so, at box 360, it determines that at least the current Vsense signal meets the oversensing criterion required for delayed VT / VF detection. (The above is combined with...) Figure 9 The incorporated references provide methods for determining when the PWOS standard is met.

[0181] At box 355, control circuit 80 determines whether environmental noise standards are met. (As mentioned above...) Figure 9 As described, the interpeak amplitudes determined from the pulsation signal segment for determining the state of the PWOS criterion can also be used to determine the state of the ambient noise criterion. Therefore, at block 355, control circuitry 80 can analyze the interpeak amplitudes of the pulsation signal segment to determine when a relatively high number of interpeak amplitudes corresponding to the most recent Vsense signal are less than a noise amplitude threshold. Ambient noise can manifest as multiple small peak amplitude signals between relatively large peak amplitude R waves in the sensed cardiac electrical signal. Therefore, the threshold number of relatively small interpeak amplitudes of the pulsation signal segment associated with the Vsense signal can indicate that ambient noise is being over-sensitized as R waves. When the ambient noise criterion is met at block 355, control circuitry 80 can determine at block 360 that the current Vsense signal meets the detection delay over-sensitization criterion.

[0182] At block 356, control circuitry 80 determines whether the TWOS criterion is met. If so, control circuitry 80 determines at block 360 that at least the current Vsense signal meets the oversensing criterion required for delayed VT / VF detection. (The above is combined with...) Figure 9 The incorporated references provide examples of the TWOS standard.

[0183] At block 358, control circuitry 80 determines whether EMI standards are met. If so, control circuitry 80 determines at block 360 that at least the current Vsense signal meets the oversensing standard required for delayed VT / VF detection. (The above is combined with...) Figure 9 The incorporated references provide examples of EMI standards.

[0184] If none of the criteria used for detecting EV noise (the "No" branch of box 352), PWOS (box 354), ambient noise (box 355), TWOS (box 356), or EMI (box 358) are met, the control circuit 80 may determine at box 362 that the oversensing criterion is not met on the current Vsense signal. The control circuit 80 may record a "0" for the current Vsense signal in the detection delay data buffer of memory 82. The current Vsense signal is not counted until the detection delay criterion for initial delay VT / VF detection is met or after the initial detection delay has expired (e.g., as described above). Figure 6 and Figure 7 (As described).

[0185] Although Figure 10 Blocks 352 to 358 are shown in a specific order, but it should be understood that the control circuit 80 can be configured to interact with... Figure 10 The different sequences shown determine the state of one or more different types of oversensing criteria. Furthermore, control circuitry 80 can determine in a parallel processing method whether multiple different types of oversensing criteria are met, such that the state of each of the EMG noise criterion, PWOS criterion, ambient noise criterion, TWOS criterion, and EMI criterion, as well as an indication of the overall oversensing criterion state (at block 360 or block 362), can be concurrently updated in memory 82 for the current Vsense signal, depending on whether at least one of the oversensing criteria is met at blocks 352, 354, 355, 356, or 358.

[0186] Figure 11 A conceptual diagram 400, based on some examples of detection delay data stored in a buffer allocated in memory 82, is used to facilitate determining when a detection delay criterion is met. When the detection delay criterion (as determined by control circuitry 80) is met, the initiation of VT / VF detection for anti-tachyarrhythmia therapy can be delayed. Combined with... Figure 10 Methods to describe Figure 11The buffer shown illustrates a method for determining when a first delay criterion is met based on multiple sets of oversensing criteria, each set of oversensing criteria being applied to a consecutive series of Vsense signals ending with the current Vsense signal. When other criteria (e.g., supraventricular rhythm criteria or other oversensing criteria) are included in the first delay criterion, additional buffers can be allocated to store the states of these criteria.

[0187] refer to Figure 10 A set of First-In-First-Out (FIFO) buffers 408 can be allocated to store the status of the EMI criterion, electromyographic noise criterion, ambient noise and PWOS (noise / PWOS) criterion, and TWOS criterion for each of the Y Vsense signals (e.g., 12 Vsense signals as shown in this exemplary example). For a corresponding Vsense signal 404, the status of each of these types of oversensing criteria is indicated by a "1" for satisfaction or by a "0" for non-satisfaction. It should be understood that the status of a given Vsense signal does not necessarily mean that the given Vsense signal is an oversensitized noise signal or a cardiac event signal. Rather, the status of a given Vsense signal indicates that, based on the analysis of one or more cardiac signals sensed by the sensing circuit 86 on a specified number of previous Vsense signals, an oversensitization criterion for noise or cardiac signal is met on the Vsense signal. For example, a "1" in the first Vsense signal in the electromyographic noise standard buffer might indicate that, based on the noise pulse count, at least three Vsense signals (or other percentages or X out of Y) from the eight most recent Vsense signals preceding the first Vsense signal are identified as noise pulses. The first Vsense signal with a state of "1" in the electromyographic noise standard may or may not be a noise pulse, but according to the electromyographic noise standard, at least a threshold number of the most recent Vsense signals (e.g., those preceding but not preceding the first Vsense signal) are considered noise pulses. Figure 11 (As shown in the image) is identified as noise pulsation.

[0188] In some examples, the state shown in the oversensing criterion buffer 408 can represent a state that meets or does not meet a specific oversensing criterion, such as, for example, in combination with Figure 9 and Figure 10As described. In the example where no VT / VF rejection rule is met as the second VT / VF rejection criterion, the applied criteria may be a subset of similar VT / VF rejection rules. A given rejection rule may include the same or similar oversensing criteria applied to the state of one of the oversensing criterion buffers 408. For example, the EMI criteria applied to the first buffer filling the oversensing criterion state buffer 408 may be a subset of the criteria applied in the EMI rejection rule. The EMG criteria applied to the second buffer filling the buffer 408 may be a subset of the criteria applied in the EMG noise rejection rule, and so on. The criteria applied to determine the state of each corresponding oversensing criterion buffer 408 may include or may not include all criteria required to meet similar VT / VF rejection rules. Furthermore, in some examples, the VT / VF rejection rule may not be applied as the second VT / VF detection criterion, for example, as combined above. Figure 6 The method described in flowchart 150. In some examples, it may be omitted. Figure 11 The buffer 414 shown here for illustrative purposes indicates whether at least one VT / VF rejection rule is satisfied on a given Vsense signal.

[0189] In other examples, the state shown in the oversensitivity criterion buffer 408 may represent the state corresponding to a VT / VF rejection rule. In some cases, a given rejection rule may include additional criteria for satisfying the rejection rule, such as a group of Vsense signals less than a certain percentage being identified as VT / VF morphological beats or other criteria. An EMI criterion state may be a state of an EMI rejection rule. An EMP noise criterion state may be a state of an EMP noise rejection rule, and so on. Therefore, the state input in a given buffer may correspond to the state of an oversensitivity criterion, which in various examples may be a subset of a VT / VF rejection rule, or it may be a state of a rejection rule.

[0190] Control circuit 80 can perform an OR operation on the states of these sets of oversensing criteria, as shown by buffer 408 on each Vsense signal, to determine and store oversensing criterion state 410. In this exemplary example, the EMI noise criterion is not met at any of the 12 Vsense signals, as shown in state 0. The EMI noise criterion is met at the times of the first two Vsense signals and the fifth Vsense signal, as shown in state 1.

[0191] The noise / PWOS criterion is satisfied at the time of each of the third, fourth, seventh, and ninth through eleventh Vsense signals, as indicated by state 1. In the example shown, the buffered PWOS and ambient noise criterion states are shown in a combined oversensitivity criterion state buffer because both may depend on the analysis of the interpeak amplitude of the pulsating signal segments, as described above. Therefore, control circuitry 80 can update the state of this combined buffer based on the satisfaction of either the ambient noise criterion or the PWOS criterion, which is based at least on the interpeak amplitude of the buffered 12 (or other number) most recent Vsense signals. In this illustrative example, the EMI and TWOS criteria are not satisfied during the time span of 12 Vsense signals, as indicated by the "0" for each Vsense signal.

[0192] For each Vsense signal associated with satisfying at least one of the oversensing criteria, the control circuit 80 may determine the overall oversensing criterion state 410 as positive, as indicated by state 1. Therefore, the overall oversensing criterion state 410 on a given Vsense signal represents an OR operation performed on the states of the individual oversensing criterion buffers 408 on the given Vsense signal. It should be noted that, for illustrative and explanatory purposes, Figure 11 The diagram illustrates the overall oversensing criterion state 410, and this overall oversensing criterion state may not necessarily be included in the memory 82 as an actual buffer. Instead, in some examples, when the NID condition is met and no VT / VF rejection rule is met, the control circuitry 80 may evaluate the data stored in the oversensing criterion buffer 408, for example by performing an OR operation on the states buffered together in the oversensing criterion buffer 408, to determine whether the detection delay criterion is met, without having to track the results of the OR operation in the individual buffer 410.

[0193] To support the determination of when the detection delay criterion is met, control circuitry 80 can buffer the morphological classification of the pulsation signal segment associated with each Vsense signal in the VT / VF pulsation morphology buffer 412. (The following is in conjunction with...) Figure 12 An example method is described for determining whether a pulsation signal segment associated with a Vsense signal represents a VT / VF pulsation pattern or a non-VT / VF pulsation pattern. In this case, control circuit 80 classifies the pulsation signal segments of the third and twelfth Vsense signals as VT / VF pulsation patterns.

[0194] In this example, NID 402 is satisfied at the time of the first Vsense signal. As described above, when the VTI / VFI counter starts to increment, for example, when it reaches a threshold less than NID (such as a value of 2, 3, 5, or other specified value), detection delay data is acquired and buffered in memory 82 so that data for determining whether the detection delay criterion is met is available when NID is reached. In some examples, control circuitry 80 may determine whether the detection delay criterion is met when NID is reached. However, in the example shown, when NID is reached, control circuitry 80 may determine whether any VT / VF rejection rule is met as a second VT / VF detection criterion, as described above. Figure 7 As described. On each of the first through eleventh Vsense signals, at least one VT / VF rejection rule is satisfied (as indicated by a "1" state). When NID is satisfied, the state of VT / VF rejection rule 414 is shown as "1". The rejection rule satisfied on each of these Vsense signals can be any of a plurality of applied rejection rules, which can typically be supraventricular rhythm rejection rules (e.g., SVT rejection rule or atrial fibrillation rejection rule) or oversensing rejection rules (e.g., EMI rejection rule, electromyographic noise rejection rule, PWOS rejection rule, TWOS rejection rule, etc.).

[0195] When a rejection rule is met, control circuit 80 may pause VT / VF detection based on NID satisfaction until at least the next Vsense signal. When any rejection rule is met, control circuit 80 may be unsure whether the detection delay criterion is met, but may continue updating the detection delay data buffer in memory 82.

[0196] In this exemplary example, Figure 11 On the last (twelfth) Vsense signal shown, the VT / VF rejection rule status is "0", indicating that no rejection rule is met on the twelfth Vsense signal. NID is still satisfied, making both the first and second VT / VF detection criteria satisfied in this case. In response to satisfying the VT / VF detection criteria, the control circuit 80 uses buffered detection delay criterion data to determine whether the detection delay criterion is satisfied.

[0197] In this scenario, more than 50% of the 12 Vsense signals (9 out of 12 Vsense signals in this case) meet the overall oversensing criterion. It should be noted that each value in the 408 buffer for a given oversensing criterion represents a determination made based on a series of Vsense signals included in a specified number of Vsense signals preceding the current Vsense signal. When one or more cardiac electrical signals sensed during multiple series (or groups) of Vsense signals (12 series of Vsense signals in this case) within a threshold number of times, in [the context of the original text, the original text is missing]. Figure 11 The first delay criterion is met on the last Vsense signal shown. The number of Vsense signals in each of the 12 series of Vsense signals evaluated to determine when a given oversensing criterion, represented by buffer 408, is met may vary, for example, depending on the applied oversensing criterion. For example, the myoelectric noise criterion may be met when at least 3 of the 8 pulsation signal segments obtained in response to 8 Vsense signals are identified as noise signal segments. However, the noise / PWOS criterion may be met when PWOS is detected on at least 3 of the 12 Vsense signals. In other examples, a single oversensing criterion may evaluate at least one cardiac signal sensed on the same specified number of Vsense signals (for example, this could be 6 to 20 Vsense signals). For example, if each individual oversensing criterion is evaluated on the most recent 8 Vsense signals, the control circuit 80 may determine that the first delay criterion is met when at least half of the 8 Vsense signals in the twelve consecutive groups of 12 satisfy at least one type of oversensing criterion.

[0198] Control circuit 80 can apply a first delay criterion to consecutive groups or series of Vsense signals, each ending with the current Vsense signal. When a threshold number of consecutive groups of Vsense signals (e.g., each ending with...) are... Figure 11 The first delay criterion is satisfied when at least half of the 12 groups or series of Vsense signals that the current Vsense signal ends meet at least one of the oversensing criteria.

[0199] In this example, less than 50% of the Vsense signals (2 out of 12 Vsense signals in this example) satisfy the VT / VF pulsation morphology criteria. Each buffer value of the VT / VF pulsation morphology criteria can represent a determination made for the current Vsense signal (or, in some cases, the preceding Vsense signal when processing time requires a delay to update the VT / VF pulsation morphology criteria state). Therefore, control circuit 80 can determine whether the detection delay criteria are met based on detection delay criterion data buffered for the first delay criteria (buffers 408 and 410) and the second delay criteria (buffer 412). When NID is still satisfied and no VT / VF rejection rule is satisfied, control circuit 80 can initiate detection delay interval 416 in response to satisfaction of the detection delay criteria. Figure 11 As observed, even if VT / VF pulsation patterns can be detected during Y Vsense signals (in this case, 2 out of 12 Vsense signals or less than 50% of Vsense signals), VT / VF detection can be delayed to allow time for temporary or intermittent oversensitivity of noise or cardiac event signals to subside if the oversensitivity detection criteria are consistently met (e.g., at least 50% of Vsense signals).

[0200] Control circuit 80 can continue filling on a first-in, first-out basis during the detection delay interval 416. Figure 11 The buffers are shown. However, the control circuit 80 may not evaluate the state of the buffers during the detection delay interval 416, so that no VT / VF detection is performed at least before the detection delay interval 416 expires. In some examples, the control circuit 80 may analyze the incoming Vsense signal pulsation segment to detect the termination of VT / VF. If the termination criterion is met during the detection delay interval 416, the control circuit 80 may reset all buffers and VTI / VFI counters and transition to an indifferent sensing state (such as...). Figure 5 (As shown).

[0201] When the detection delay interval 416 expires, if the NID is still satisfied, the control circuit 80 may resume evaluating the oversensing criterion state and VT / VF pulsation morphology state on each Vsense signal received from the sensing circuit 86 until a VT / VF is detected (not satisfying the detection delay criterion, satisfying the NID, and not satisfying any rejection rule), until the termination criterion is satisfied, or until the maximum detection delay interval expires (causing VT / VF detection), whichever comes first. After the initial detection delay interval 416 expires for the first time, the NID, detection delay criterion, and VT / VF rejection rule may be evaluated for each Vsense signal (e.g., pulsatically). In other examples, the detection delay interval 416 may be restarted whenever the detection delay criterion is satisfied until the maximum number of times is reached, and / or a shorter detection delay interval may be started when the detection delay criterion is satisfied again after the initial delay interval 416 expires.

[0202] Figure 12 This is a flowchart 450 illustrating methods for determining morphological evidence of true VT / VF beats to determine when a detection delay criterion is met, based on several examples. The detection delay criterion may not be met when one or more (e.g., at least a threshold percentage) VT / VF morphological beats are identified from a specified number of recent Vsense signals. In some cases, noise contamination of cardiac signals and / or oversensing of cardiac events may occur concurrently with a true VT / VF episode. Therefore, when a first delay criterion (related to oversensing and / or supraventricular rhythm criteria) is met, control circuitry 80 may require fewer than a threshold number of beat signal segments associated with recent Vsense signals to be identified as VT / VF morphological beats in order to delay VT / VF detection.

[0203] Control circuit 80 analyzes pulsation signal segments of rectified cardiac signals to detect VT / VF pulsation morphology. Pulsation signal segments can be received from morphology signal channel 87, but in other examples, they can be received from any of the sensing channels 83, 85, or 87 of sensing circuit 86. The pulsation signal segments can extend for a specified time interval before and after the Vsense signal, such that the pulsation signal segments are acquired relative to a single Vsense signal. A single Vsense signal may be encompassed by the pulsation signal segments. However, in some cases, when the Vsense signal appears at a rapid rate, a second Vsense signal may appear near the beginning or end of the pulsation signal segment, depending on the duration of the pulsation signal segment. However, the pulsation signal segments are acquired relative to a single Vsense signal such that each pulsation signal segment extends for a specified time interval before and after the triggering of the Vsense signal.

[0204] The pulsating signal segment can be a broadband and notch-filtered segment of the sensed cardiac signal. For example, control circuit 80 can buffer from, for example... Figure 4 The rectified notch-filtered signal 79 received by the morphological signal channel 87 is used to obtain a pulsating signal segment that corresponds in time to a single-channel Vsense signal received from one of the selected sensing channels 83 or 85. It should be understood that one Vsense signal can be received from each of the sensing channels 83 and 85 during the pulsating signal segment, and all Vsense signals correspond to a signal waveform exceeding the R-wave sensing threshold in at least one of the sensing channels 83 or 85. The duration of the pulsating signal segment can be from 200 ms to 500 ms, and as an example, the duration can be from 300 ms to 400 ms. In the illustrative example, the pulsating signal segment extends for 360 ms before and after the Vsense signal received from the selected sensing channel 83 or 85. In one example, when the sampling rate is 256 Hz, the pulsation signal segment may include 92 sampling points, of which 68 sampling points are earlier than the time of the stored Vsense signal that triggers the pulsation signal segment, and 24 sampling points include the Vsense signal and extend after the Vsense signal.

[0205] Control circuit 80 can determine a signal amplitude at block 452 and a signal width metric at block 454. The signal amplitude quantifies the deviation of the signal waveform from an isoelectric baseline. A relatively large signal amplitude is an indication of the true VT / VF pulsation morphology (e.g., fibrillation waveform). The signal width metric quantifies the width of the signal pulse in the signal waveform of the pulsating signal segment. A relatively large signal width metric is evidence of the true VT / VF pulsation morphology, because a relatively narrow signal width metric can be evidence, for example, of an R wave conducted from the atrium during sinus tachycardia or SVT, or of a narrow noisy signal pulse (e.g., an EMI pulse).

[0206] In some examples, control circuitry 80 may determine the signal amplitude at block 452 by determining the maximum absolute amplitude of the rectified notch-filtered pulsating signal segment. Control circuitry 80 may sum the amplitudes of all sample points of the rectified signal segment, which may represent the area of ​​the rectified signal segment. Control circuitry 80 may determine the signal amplitude based on the maximum absolute amplitude and the summed sample point amplitudes (area). In one example, the signal amplitude is determined as a predetermined multiple or weighted sum of the amplitudes of all sample points of the broadband-filtered, notch-filtered, and rectified pulsating signal segment normalized to the maximum absolute amplitude. The signal amplitude determined in this way may be referred to as the "Normalized Mean Rectified Amplitude" (NMRA). In one example, NMRA may be determined as four times the summed sample point amplitude divided by the maximum absolute amplitude, which may be truncated to an integer value.

[0207] The magnitude of the signal amplitude (e.g., determined as NMRA) may be negatively correlated with the probability that a signal segment sampling point is at or near the baseline amplitude during a specified duration of the pulsating signal segment. A higher NMRA indicates a lower probability that the signal is at or near the baseline amplitude at any given point in time during the pulsating signal segment. A relatively low probability that a signal sampling point is at or near the baseline during the pulsating signal segment may be associated with tachyarrhythmia morphologies (e.g., possibly resembling ventricular fibrillation morphologies with relatively large sinusoidal signals). A relatively high probability that a signal sampling point is at or near the baseline during the pulsating signal segment may be associated with the presence of a relatively narrow normal R-wave signal during the pulsating signal segment, or with the absence of a true R-wave, such as the presence of a baseline amplitude portion of the signal segment or low-amplitude noise pulses before and after the Vsense signal.

[0208] Control circuit 80 can compare the signal amplitude amount with an amplitude threshold at block 452. When the signal amplitude amount does not meet the threshold, control circuit 80 can identify the current Vsense signal as a non-VT / VF pulsation pattern. In one example, the threshold applied to NMRA is 100 to 150 or 110 to 130, and in various examples it is between 120 and 128. For example, when NMRA is determined as described above and is at least 125, for example, when 92 sampling points are summed, multiplied by a weighting factor of 4, and normalized by the maximum absolute amplitude, control circuit 80 can determine the signal amplitude amount that satisfies the detection of VT / VF pulsation patterns. However, it should be recognized that the value of the threshold applied to the signal amplitude amount to detect VT / VF pulsation patterns can depend on various factors, such as the amplification and number of sampling points being summed, the multiplication or weighting factor of the summed sampling points, filtering applied to the signal segment, etc.

[0209] At block 454, control circuitry 80 can determine a signal width metric by identifying signal pulses within a pulsating signal segment and determining the maximum pulse width from the identified signal pulses. For example, using the same rectified, broadband-filtered, and notch-filtered signal segment used to determine the signal amplitude, control circuitry 80 can determine a pulse amplitude threshold based on, for example, a percentage of the maximum absolute amplitude of the signal segment. In one example, the pulse amplitude threshold is half the maximum absolute amplitude of the signal segment, but other percentages can be used. Control circuitry 80 can identify signal pulses within a rectified signal segment that have the maximum amplitude that satisfies the pulse amplitude threshold. For each signal pulse in the identified signal pulses, control circuitry 80 can determine the signal pulse width as the number of sampling points (or corresponding duration) of the signal pulse between the start baseline point and the end baseline point (e.g., a zero-amplitude sampling point or a zero-crossing point of an unrectified signal). From the signal pulse widths determined for the identified signal pulses, control circuitry 80 can determine the maximum signal pulse width as a signal width metric at block 454.

[0210] The control circuit 80 can compare a signal width metric with a width threshold at block 454. When the signal width metric is determined to be the maximum signal pulse width as described above, the threshold applied at block 454 can be between 10 and 30 samples, and in one example, 20 samples, for example, when the sampling rate is 256 Hz.

[0211] exist Figure 12 In the example shown, control circuit 80 can determine when the signal amplitude meets the amplitude threshold applied at block 452, and when the signal width measure meets the width threshold applied at block 454. When both requirements are met, control circuit 80 can determine at block 456 that the Vsense signal is associated with the true VT / VF pulsation pattern of the corresponding pulsation signal segment. When neither of these requirements is met (the "No" branch of block 452 or the "No" branch of block 454), control circuit 80 can determine at block 458 that the Vsense signal is associated with a non-VT / VF pulsation pattern of the pulsation signal segment. However, it is envisioned that control circuit 80 does not need to require both the signal amplitude and the signal width measure to be greater than the corresponding thresholds simultaneously, but rather can classify the pulsation signal segment as a VT / VF pulsation pattern when either the signal amplitude or the signal width measure meets the corresponding amplitude threshold or width threshold.

[0212] Control circuit 80 can classify and buffer the morphology of pulsation signal segments into VT / VF morphologies (e.g., Figure 11 The “1” in VT / VF pulsation morphology buffer 412) or non-VT / VF morphology (e.g., Figure 11 (The "0" in VT / VF pulsation morphology buffer 412). See again. Figure 8 At box 254, control circuit 80 can determine how many of the most recent M Vsense signals are related to the data... Figure 12 The method is used to determine the correlation between VT / VF pulsation patterns. For example, when less than 50% of the most recent M Vsense signals are associated with the VT / VF pulsation pattern of the corresponding pulsation signal segment, the control circuit 80 can determine at block 258 that the detection delay criterion is met. When at least 50% of the most recent M Vsense signals are identified as VT / VF pulsations, the control circuit 80 can determine at block 256 that the detection delay criterion is not met.

[0213] Figure 13 This is a flowchart 500 based on some examples of methods for adjusting tachyarrhythmia interval counters. (As described above...) Figure 5 As described, control circuitry 80 can monitor one or more NSR beats that may indicate a possible interruption of the VT / VF rhythm. Control circuitry 80 can begin monitoring NSR beats when the VTI / VFI counter is at a non-zero value (e.g., at least 2, 3, 5 or greater).

[0214] In response to receiving a Vsense signal from the selected sensing channel 83 or 85 at block 502, control circuitry 80 may (at block 504) determine an RRI that ends with the received Vsense signal and begins with the most recent preceding Vsense signal. In some cases, an RRI may begin or end with a ventricular pacing pulse. In other examples, for the purpose of detecting NSR beats, an RRI that begins or ends with a ventricular pacing pulse may be ignored.

[0215] At block 505, control circuitry 80 can determine morphological features from a pulsatile signal segment associated with the Vsense signal. For example, at block 505, a morphological match score can be determined between the pulsatile signal segment associated with the received Vsense signal and an R-wave template stored in memory 82. As discussed above, an R-wave template can be established during a known NSR, for example, to represent a normally conducted R-wave. Other examples of morphological features that can be determined at block 505 are described below in conjunction with block 508.

[0216] At block 506, control circuitry 80 can compare the RRI with a corresponding threshold. Control circuitry 80 can determine a pause threshold based on the most recently determined RRI. For example, control circuitry 80 can identify each RRI greater than a long period threshold. The long period threshold can be the VF detection interval plus an offset. If VT detection is enabled, the long period threshold can be the VT detection interval plus an offset. As an example, the offset can be 30ms to 80ms or 60ms. Control circuitry 80 can determine a pause threshold based on RRIs determined from Vsense signals received that are greater than the long period threshold. For example, the pause threshold can be set as a percentage of the mean or median of RRIs greater than the long period threshold. This percentage can be 50% to 80%, and in one example, it can be 75%.

[0217] If the RRI ending with the current Vsense signal does not meet the pause threshold (the "No" branch of block 506), the control circuit 80 can determine that no NSR pulsation was detected at block 510 and return to block 502 to wait for the next Vsense signal. If the RRI ending with the current Vsense signal is greater than the pause threshold, the control circuit 80 can determine at block 508 whether the morphological feature determined for the current Vsense signal corresponding to the end of the RRI or the morphological feature determined for the previous Vsense signal corresponding to the beginning of the RRI meets the NSR morphological criteria.

[0218] When the morphological match score determined at box 505 is greater than a match threshold (e.g., in the range of 0 to 100, where the nominal match threshold may be between 50 and 70 or 60), the pulsating signal segment can be identified as an NSR morphological pulsation at box 508. As a supplement to or alternative to determining the morphological match score at box 505, control circuitry 80 can determine other characteristics of the pulsating signal segment to identify a conducting supraventricular rhythmic pulsation. In one example, signal width, peak polarity pattern, and / or peak time from the Vsense signal (exceeding the R-wave sensing threshold) to the maximum absolute peak can be determined. At box 508, one or more characteristics determined from the pulsating signal segment can be compared to corresponding thresholds or ranges representing R waves conducted from the atrium.

[0219] If, at block 508, it is determined that the pulsation signal segment associated with both the leading and trailing Vsense signals does not meet the NSR morphology criteria, the control circuit 80 may determine at block 510 that no NSR pulsation was detected. The control circuit 80 may then return to block 502 to wait for the next Vsense signal.

[0220] An NSR pulsation can be detected at box 511 when at least one of the leading or trailing Vsense signals (with an RRI greater than the pause threshold) at box 508 is associated with a pulsating signal segment classified as NSR morphology. Control circuitry 80 can update the NSR pulsation count at box 512, for example, by storing the NSR or non-NSR pulsation classification determined for the current Vsense signal in a buffer in memory. In one example, the FIFO buffer stores the latest classification for each of a specified number of Vsense signals (e.g., 6 to 20 or 16 Vsense signals).

[0221] At block 514, control circuitry 80 can determine whether a reset criterion is met. Control circuitry 80 can determine, for example, whether at least a threshold number of NSR beats are identified based on the updated NSR beat count determined at block 512. In one example, the reset criterion is met at block 514 if at least one-eighth (e.g., 2 out of 16) of the Vsense signals are identified as NSR beats.

[0222] In some examples, when a threshold number of NSR pulsations are detected and it is determined that a Vsense signal less than a threshold percentage is associated with the VT / VF pulsation morphology of the corresponding pulsation signal segment, the control circuit 80 can determine that the reset criterion is met. The control circuit 80 can then, in conjunction with the above... Figure 12 Any of the examples described are used to detect VT / VF morphology. If more than a threshold percentage of the most recent Vsense signals are identified as VT / VF morphological pulsations, the reset criterion may not be met at box 514. In the illustrative example of buffering the NSR pulsation count of the most recent 16 Vsense signals, when fewer than 10 of the 16 Vsense signals are identified as VT / VF morphological pulsations (e.g., based on...),... Figure 12 When the method is used, the control circuit 80 can determine that the reset criteria are met.

[0223] In some examples, control circuitry 80 determines that a reset criterion is met only if the VTI / VFI counter has reached at least a threshold. In an exemplary example, control circuitry 80 may determine that a reset criterion is met when the VFI counter is at least 5, 7, 10, 12, or other thresholds, or when the combined VTI / VFI counter (when VT detection is enabled) is at least 8, 10, 12, or other thresholds, by combining the required NSR pulse count with a threshold number less than VT / VF morphological pulses. In one example, control circuitry 80 may determine that a reset criterion is met at block 512 when the VTI / VFI counter has reached at least a threshold number, at least one-eighth of the Y most recent Vsense signals are NSR pulses, at least one or more of the NSR pulses are within the most recent 2 to 4 Vsense signals, and less than 60% of the Vsense signals are classified as VT / VF morphological pulses.

[0224] When the reset criteria are not met, control circuitry 80 may return to block 502 to wait for the next Vsense signal. When the reset criteria are met, control circuitry 80 may decrease the VTI / VFI counter to a lower value. In some examples, the VTI / VFI counter (and the combined counter, if used) may be reset to 0. In other examples, the VTI / VFI counter may be reset to a value of 2, 3, 4, 5, or other selected values ​​less than NID and less than the current counter value. In an exemplary example, the VFI counter is reset to 3, and the VTI counter is reset to 2. In other examples, the VTI / VFI counter may be decreased from its current value by a specified amount.

[0225] Figure 13 The method can be achieved by control circuit 80 in box 102 ( Figure 5 Irrelevant state 1 or box 104 () Figure 5 This operation is executed under state 2. It can be executed whenever the VTI / VFI counter is at least the threshold (i.e., less than NID) and no VT / VF detection has been performed. Figure 13 The method. Control circuit 80 can be executed before or after reaching NID. Figure 13 The method. If NID has been achieved, then when the control circuit 80 suspends VT / VF detection due to the rejection rule and VT / VF is not detected, and / or when VT / VF detection is delayed due to the detection delay criterion, the control circuit 80 may execute... Figure 13 The method.

[0226] This document also discloses the subject matter of the following embodiments: Example 1. A medical device comprising a sensing circuit configured to sense one or more cardiac electrical signals and to sense ventricular event signals from the one or more cardiac electrical signals. The medical device may include control circuitry in communication with the sensing circuitry. The control circuitry may be configured to determine that the one or more cardiac electrical signals meet a tachyarrhythmia detection criterion, apply a first delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of sets of ventricular event signals sensed by the sensing circuitry, and determine that a detection delay criterion is met by determining that at least a threshold number of sets of the plurality of ventricular event signals sensed by the sensing circuitry meet at least the first delay criterion. In response to meeting the detection delay criterion, the control circuitry may delay the detection of the tachyarrhythmia based on meeting the tachyarrhythmia detection criterion. The medical device may include a treatment delivery circuit configured to initiate anti-tachyarrhythmic treatment when the control circuit detects the tachyarrhythmia, and the initiation of the anti-tachyarrhythmic treatment is also delayed when the detection of the tachyarrhythmia is delayed by the control circuit.

[0227] Example 2. According to the medical device of Example 1, wherein the control circuit is further configured to apply a second delay criterion by: for each of a plurality of ventricular event signals sensed by the sensing circuit, obtaining a pulsating signal segment from the one or more cardiac electrical signals in response to the ventricular event signal among the plurality of ventricular event signals; and determining whether the pulsating signal segment satisfies a tachyarrhythmia morphology criterion. The control circuit may be further configured to determine that the second delay criterion is met by determining that a number of pulsating signal segments less than a threshold number satisfy the tachyarrhythmia morphology criterion. The control circuit may determine that the detection delay criterion is met by determining that both the first delay criterion and the second delay criterion are satisfied.

[0228] Example 3. The medical device according to Example 2, wherein the control circuit is further configured to determine whether the pulsating signal segment meets the tachyarrhythmia morphology criteria by: determining a signal amplitude based on the pulsating signal segment; determining a signal width metric based on the pulsating signal segment; and determining that the pulsating signal segment meets the tachyarrhythmia morphology criteria when at least one of the signal amplitude satisfying a first threshold or the signal width metric satisfying a second threshold is met.

[0229] Example 4. The medical device according to any one of Examples 1 to 3, wherein the control circuit is further configured to determine whether the rapid arrhythmia detection rejection criterion is not met in response to meeting the rapid arrhythmia detection criterion, and to determine whether the detection delay criterion is met in response to meeting the rapid arrhythmia detection criterion but not meeting the rapid arrhythmia rejection criterion.

[0230] Example 5. A medical device according to any one of Examples 1 to 4, wherein the control circuit is further configured to delay the detection of the tachyarrhythmia by activating a detection delay interval. The control circuit can determine that the detection delay interval has expired, and can determine that the tachyarrhythmia detection criteria are still met after the detection delay interval has expired. In response to the tachyarrhythmia detection criteria still being met, the control circuit can determine whether the detection delay criteria are still met. In response to both the tachyarrhythmia detection criteria and the detection delay criteria still being met, the control circuit can continue to delay the detection of the tachyarrhythmia.

[0231] Example 6. A medical device according to any one of Examples 1 to 5, wherein the control circuit is further configured to delay the detection of the tachyarrhythmia by activating a detection delay interval, determine that the detection delay interval has expired, and determine that the tachyarrhythmia detection criteria are still met after the detection delay interval has expired. The control circuit may determine that the tachyarrhythmia detection rejection criteria are not met, and in response to whether the tachyarrhythmia detection criteria are still met and the tachyarrhythmia detection rejection criteria are not met, determine whether the detection delay criteria are still met. If the detection delay criteria are still met, the control circuit may continue to delay the detection of the tachyarrhythmia until at least one next ventricular event signal sensed by the sensing circuit.

[0232] Example 7. The medical device according to any one of Examples 5 to 6, wherein the control circuit is further configured to restart the detection delay interval in response to the detection delay criterion still being met.

[0233] Example 8. The medical device according to any one of Examples 1 to 7, wherein the control circuit is further configured to initiate a maximum time delay in response to meeting the detection delay criterion.

[0234] Example 9. The medical device according to Example 7, wherein the control circuit is further configured to determine the expiration of the maximum time delay and to detect the tachyarrhythmia in response to the expiration of the maximum time delay.

[0235] Example 10. A medical device according to any one of Examples 1 to 9, wherein the control circuit is further configured to determine that the first delay criterion is met by determining that at least a portion of a group of the number of thresholds among the plurality of groups of ventricular event signals sensed by the sensing circuit meets the oversensing criterion.

[0236] Example 11. The medical device according to Example 10, wherein the control circuit is further configured to determine that at least a portion of a group of the threshold number of the plurality of ventricular event signals satisfies the oversensing criterion by: for each of the plurality of ventricular event signals, obtaining a pulsating signal segment associated with each of the plurality of ventricular event signals; identifying the pulsating signal segment as a noise signal segment; and determining whether the group of the plurality of ventricular event signals satisfies the noise oversensing criterion based on the pulsating signal segment identified as a noise signal segment.

[0237] Example 12. A medical device according to any one of Examples 10 to 11, wherein the control circuitry is further configured to determine that at least a portion of a group of the number of thresholds among the plurality of groups of ventricular event signals satisfies the oversensing criterion by: for each of the plurality of groups of ventricular event signals, obtaining a pulsation signal segment associated with each of the plurality of ventricular event signals; identifying cardiac event oversensing from the pulsation signal segment; and determining whether the group of the plurality of groups of ventricular event signals satisfies the cardiac event oversensing criterion based on the cardiac event oversensing identified at least from the pulsation signal segment.

[0238] Example 13. The medical device according to any one of Examples 1 to 12, wherein the control circuit is further configured to determine that the first delay criterion is met by determining that one or more of the groups of the number of thresholds among the plurality of groups of ventricular event signals sensed by the sensing circuit meet the supraventricular rhythm criterion.

[0239] Example 14. A medical device according to any one of Examples 1 to 13, wherein the control circuit is further configured to determine that the detection delay criterion is not met, and to detect the tachyarrhythmia based on meeting the tachyarrhythmia detection criterion and not meeting the detection delay criterion. The treatment delivery circuit may include a capacitor, and the treatment delivery circuit is further configured to initiate the anti-tachyarrhythmia treatment by initiating charging of the capacitor to deliver the anti-tachyarrhythmia treatment in response to the control circuit detecting the tachyarrhythmia.

[0240] Example 15. The medical device according to any one of Examples 1 to 14, wherein the control circuit is further configured to determine that the rapid arrhythmia detection criteria are met by at least the following means: determining the ventricular event interval based on the sensed ventricular event signal; and determining the number of rapid arrhythmia intervals reaching the threshold based on the determined ventricular event interval.

[0241] Example 16. A method comprising: sensing one or more cardiac electrical signals; sensing ventricular event signals from the one or more cardiac electrical signals; and determining that the one or more cardiac electrical signals meet a tachyarrhythmia detection criterion. The method may further comprise applying a first delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of sets of sensed ventricular event signals. The method may further comprise determining that a detection delay criterion is met by determining that at least a threshold number of sets of the plurality of sensed ventricular event signals meet at least the first delay criterion. The method may include: delaying the detection of a tachyarrhythmia based on meeting the tachyarrhythmia detection criterion in response to meeting the detection delay criterion; and initiating anti-tachyarrhythmic treatment in response to detecting the tachyarrhythmia, wherein the initiation of the anti-tachyarrhythmic treatment is also delayed when the detection of the tachyarrhythmia is delayed.

[0242] Example 17. According to the method of Example 16, the method further includes applying a second delay criterion by: for each of a plurality of sensed ventricular event signals, obtaining a pulsating signal segment from the one or more cardiac electrical signals in response to the ventricular event signal among the plurality of sensed ventricular event signals; and determining whether the pulsating signal segment satisfies a tachyarrhythmia morphology criterion. The method may include determining that the second delay criterion is satisfied by determining that less than a threshold number of the pulsating signal segments satisfy the tachyarrhythmia morphology criterion. The method may include determining that the detection delay criterion is satisfied by determining that both the first delay criterion and the second delay criterion are satisfied.

[0243] Example 18. According to the method of Example 17, determining whether the pulsating signal segment meets the morphological criteria for tachyarrhythmia includes: determining a signal amplitude based on the pulsating signal segment; determining a signal width metric based on the pulsating signal segment; and determining that the pulsating signal segment meets the morphological criteria for tachyarrhythmia when at least one of the signal amplitude satisfying a first threshold or the signal width metric satisfying a second threshold is met.

[0244] Example 19. The method according to any one of Examples 16 to 18, the method further comprising: determining whether the rapid arrhythmia detection rejection criterion is not met in response to meeting the rapid arrhythmia detection criterion; and determining whether the detection delay criterion is met in response to meeting the rapid arrhythmia detection criterion and not meeting the rapid arrhythmia rejection criterion.

[0245] Example 20. The method according to any one of Examples 16 to 19, further comprising: delaying the detection of the rapid arrhythmia by initiating a detection delay interval; and determining that the detection delay interval has expired. The method may further comprise: determining that the rapid arrhythmia detection criteria are still met after the detection delay interval has expired; and, in response to the rapid arrhythmia detection criteria still being met, determining whether the detection delay criteria are still met. The method may further comprise: in response to both the rapid arrhythmia detection criteria and the detection delay criteria still being met, continuing to delay the detection of the rapid arrhythmia.

[0246] Example 21. The method according to any one of Examples 16 to 20, further comprising: delaying the detection of the rapid arrhythmia by initiating a detection delay interval; determining that the detection delay interval has expired; and determining that the rapid arrhythmia detection criteria are still met after the detection delay interval has expired. The method may include: determining that the rapid arrhythmia detection rejection criteria are not met; and, in response to whether the rapid arrhythmia detection criteria are still met and the rapid arrhythmia detection rejection criteria are not met, determining whether the detection delay criteria are still met. The method may further include: if the detection delay criteria are still met, continuing to delay the detection of the rapid arrhythmia until at least the next sensed ventricular event signal.

[0247] Example 22. The method according to any one of Examples 20 to 21, the method further comprising restarting the detection delay interval in response to the detection delay criterion still being met.

[0248] Example 23. The method according to any one of Examples 16 to 22, the method further comprising initiating a maximum delay time in response to meeting the detection delay criterion.

[0249] Example 24. The method according to Example 23, the method further comprising: determining that the maximum delay time has expired; and detecting the tachyarrhythmia in response to the expiration of the maximum delay time.

[0250] Example 25. The method according to any one of Examples 16 to 24, wherein determining that the first delay criterion is satisfied includes: determining that at least a portion of a group of the number of thresholds in the plurality of groups of sensed ventricular event signals satisfies the oversensing criterion.

[0251] Example 26. The method according to Example 25, the method further comprising determining that at least a portion of the group of the multiple sets of sensed ventricular event signals satisfies the oversensing criterion by: for each of the multiple sets of sensed ventricular event signals, obtaining a pulsation signal segment associated with each of the multiple sets of sensed ventricular event signals; identifying the pulsation signal segment as a noise signal segment; and determining whether the group of the multiple sets of sensed ventricular event signals satisfies the noise oversensing criterion based on the pulsation signal segment identified as a noise signal segment.

[0252] Example 27. The method according to any one of Examples 25 to 26, wherein determining that at least a portion of a group of the plurality of sensed ventricular event signals satisfies the oversensing criterion comprises: for each of the plurality of sensed ventricular event signals, obtaining a pulsation signal segment associated with each of the plurality of sensed ventricular event signals; identifying cardiac event oversensing at least from the pulsation signal segment; and determining whether the group of the plurality of sensed ventricular event signals satisfies the cardiac event oversensing criterion based on the cardiac event oversensing identified at least from the pulsation signal segment.

[0253] Example 28. The method according to any one of Examples 16 to 27, the method further comprising determining that the first delay criterion is met by determining that one or more of the groups of the number of thresholds in the plurality of groups of sensed ventricular event signals meet the supraventricular rhythm criterion.

[0254] Example 29. The method according to any one of Examples 16 to 28, the method further comprising: determining that the detection delay criterion is not met; detecting the tachyarrhythmia based on meeting the tachyarrhythmia detection criterion and not meeting the detection delay criterion; and initiating the anti-tachyarrhythmia treatment by: starting to charge a capacitor in response to detecting the tachyarrhythmia to deliver the anti-tachyarrhythmia treatment.

[0255] Example 30. The method according to any one of Examples 16 to 29, the method further comprising determining the tachyarrhythmia detection criteria by: determining the ventricular event interval based on the sensed ventricular event signal; and determining the number of tachyarrhythmia intervals reaching the threshold based on the determined ventricular event interval.

[0256] Example 31. A non-transitory computer-readable medium storing a set of instructions, which, when executed by control circuitry of a medical device, causes the medical device to: sense one or more cardiac electrical signals; sense ventricular event signals from the one or more cardiac electrical signals; and determine that the one or more cardiac electrical signals meet a tachyarrhythmia detection criterion. The instructions may also cause the medical device to: apply a delay criterion to the one or more cardiac electrical signals sensed during each of a plurality of sets of sensed ventricular event signals; and determine that a detection delay criterion is met by determining that at least a threshold number of sets of sensed ventricular event signals meet at least the delay criterion. The instructions may also cause the medical device to: delay the detection of a tachyarrhythmia based on meeting the tachyarrhythmia detection criterion in response to meeting the detection delay criterion; and initiate anti-tachyarrhythmia treatment when the tachyarrhythmia is detected, wherein the initiation of the anti-tachyarrhythmia treatment is also delayed when the detection of the tachyarrhythmia is delayed.

[0257] It should be understood that, depending on the example, certain actions or events in any of the methods described herein may be performed in a different order, and may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for practicing the method). Furthermore, in some examples, actions or events may be performed simultaneously, for example, through multithreading, interrupt handling, or multiple processors, rather than sequentially. In addition, for clarity, although some aspects of this disclosure are described as being performed by a single circuit or unit, it should be understood that the techniques of this disclosure may be performed by a combination of units or circuits associated with, for example, a medical device.

[0258] In one or more examples, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that is accessible by a computer).

[0259] Instructions can be executed by one or more processors (such as one or more digital signal processors (DSPs)), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPLAs), or other equivalent integrated or discrete logic circuits. Therefore, as used herein, the term "processor" can refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Furthermore, these techniques can be fully implemented in one or more circuit or logic elements.

[0260] Therefore, a medical device has been presented in the foregoing description with reference to specific embodiments. It should be understood that the various aspects disclosed herein can be combined with combinations different from the specific combinations presented in the drawings. It should be understood that various modifications can be made to the reference examples without departing from the scope of this disclosure and the following claims.

Claims

1. A medical device, the medical device comprising: The sensing circuit is configured to: Sensing one or more cardiac electrical signals; as well as Sensing ventricular event signals from one or more cardiac electrical signals; A control circuit, which communicates with and is configured to: Determine that the one or more cardiac electrical signals meet the criteria for detecting rapid arrhythmias; The first delay criterion is applied to the one or more cardiac electrical signals sensed during each of the multiple sets of multiple ventricular event signals sensed by the sensing circuit; The detection delay criterion is determined by determining that at least a threshold number of the multiple sets of ventricular event signals sensed by the sensing circuit satisfy at least the first delay criterion; In response to meeting the detection delay criteria, the delay is based on meeting the tachyarrhythmia detection criteria for detecting tachyarrhythmias; and A treatment delivery circuit is configured to initiate anti-tachyarrhythmic treatment when the control circuit detects the tachyarrhythmia, and the initiation of the anti-tachyarrhythmic treatment is also delayed when the detection of the tachyarrhythmia is delayed by the control circuit.

2. The medical device according to claim 1, wherein the control circuit is further configured as follows: The second delay standard shall be applied in the following manner: For each of the multiple ventricular event signals sensed by the sensing circuit: In response to the ventricular event signal among the plurality of ventricular event signals, a pulsation signal segment is obtained from the one or more cardiac electrical signals; as well as Determine whether the pulsation signal segment meets the morphological criteria for tachyarrhythmias; The second delay criterion is determined by determining that the number of pulsating signal fragments less than a threshold satisfies the rapid arrhythmia morphology criterion; and The detection delay criterion is determined by determining whether the first delay criterion and the second delay criterion are met.

3. The medical device of claim 2, wherein the control circuit is further configured to determine whether the pulsation signal segment meets the morphological criteria for tachyarrhythmia by: The signal amplitude is determined based on the pulsating signal segment; Determine the signal width metric based on the pulsating signal segment; and When at least one of the following conditions is met: the signal amplitude meets the first threshold or the signal width meets the second threshold, the pulsating signal segment is determined to meet the morphological criteria for tachyarrhythmia.

4. The medical device according to any one of claims 1 to 3, wherein the control circuit is further configured to: In response to meeting the aforementioned rapid arrhythmia detection criteria, it is determined that the rapid arrhythmia detection rejection criteria are not met; and The determination of whether the detection delay criterion is met is made in response to the tachycardia detection criteria being met but the tachycardia rejection criteria not being met.

5. The medical device according to any one of claims 1 to 4, wherein the control circuit is further configured to: The detection of the rapid arrhythmia is delayed by initiating a detection delay interval; The detection delay interval has expired; It is determined that the rapid arrhythmia detection criteria are still met after the detection delay interval has expired; In response to the condition that the rapid arrhythmia detection criteria are still met, determine whether the detection delay criteria are still met; and In response to the fact that the tachyarrhythmia detection criteria and the detection delay criteria are still met, the detection of the tachyarrhythmia is further delayed.

6. The medical device of claim 5, wherein the control circuitry is further configured to restart the detection delay interval in response to the detection delay criterion still being met.

7. The medical device according to any one of claims 1 to 6, wherein the control circuit is further configured to initiate a maximum time delay in response to meeting the detection delay criterion.

8. The medical device according to claim 7, wherein the control circuit is further configured to: Determine the maximum time delay due date; and The rapid arrhythmia is detected in response to the expiration of the maximum time delay.

9. The medical device according to any one of claims 1 to 8, wherein the control circuit is further configured to determine that the first delay criterion is met by determining that at least a portion of a group of the number of thresholds among the plurality of groups of ventricular event signals sensed by the sensing circuit meets the oversensing criterion.

10. The medical device of claim 9, wherein the control circuitry is further configured to determine that at least a portion of a group of the number of thresholds among the plurality of groups of ventricular event signals satisfies the oversensing criterion by: For each of the multiple sets of ventricular event signals: Obtain the pulsation signal segment associated with each of the plurality of ventricular event signals; Identify pulsating signal segments that are considered noise signal segments from the plurality of ventricular event signals; as well as The group of multiple ventricular event signals is determined based on the pulsating signal segment identified as a noise signal segment to determine whether the group meets the noise oversensing criterion.

11. The medical device according to any one of claims 9 to 10, wherein the control circuitry is further configured to determine that at least a portion of a group of the number of thresholds among the plurality of groups of ventricular event signals satisfies an oversensing criterion by: For each of the multiple sets of ventricular event signals: Obtain the pulsation signal segment associated with each of the plurality of ventricular event signals; as well as At least from the pulsating signal fragments, identify the excessive sensing of cardiac events; as well as Whether a group of multiple ventricular event signals meets the criteria for excessive sensing of cardiac events is determined based on the excessive sensing of cardiac events identified at least from the pulsating signal segments.

12. The medical device according to any one of claims 1 to 11, wherein the control circuit is further configured to determine that the first delay criterion is met by determining that one or more of the groups of the number of thresholds among the plurality of groups of ventricular event signals sensed by the sensing circuit meet the supraventricular rhythm criterion.

13. The medical device according to any one of claims 1 to 12, wherein: The control circuit is further configured as follows: It is determined that the detection delay criterion is not met; and The rapid arrhythmia is detected based on meeting the aforementioned rapid arrhythmia detection criteria but not meeting the aforementioned detection delay criteria; and The treatment delivery circuit also includes a capacitor, and the treatment delivery circuit is further configured to initiate the anti-tachyarrhythmia treatment by initiating charging of the capacitor in response to the control circuit detecting the tachyarrhythmia to deliver the anti-tachyarrhythmia treatment.

14. The medical device according to any one of claims 1 to 13, wherein the control circuit is further configured to determine whether the rapid arrhythmia detection criteria are met at least by: The ventricular event interval is determined based on the sensed ventricular event signal; and The threshold number of tachyarrhythmia intervals is determined based on the established ventricular event intervals.

15. A non-transitory computer-readable medium storing an instruction set, which, when executed by control circuitry of a medical device, causes the medical device to: Sensing one or more cardiac electrical signals; Sensing ventricular event signals from one or more cardiac electrical signals; Determine that the one or more cardiac electrical signals meet the criteria for detecting rapid arrhythmias; The delay criterion is applied to the one or more cardiac electrical signals sensed during each of the multiple sets of sensed ventricular event signals; The detection delay criterion is determined by determining that at least a threshold number of the multiple sets of sensed ventricular event signals satisfy at least the delay criterion. In response to meeting the detection delay criteria, the delay is based on meeting the tachyarrhythmia detection criteria for detecting tachyarrhythmias; as well as When the tachyarrhythmia is detected, antitachyarrhythmic treatment is initiated, wherein if the detection of the tachyarrhythmia is delayed, the initiation of the antitachyarrhythmic treatment is also delayed.

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