Morphology-based detection of oversensing in medical devices

Abstract

Example systems, devices and techniques are described for morphology-based detection of oversensing. An example system includes sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient. The system includes processing circuitry configured to determine, based on the cardiac EGM data, an occurrence of an event. The processing circuitry is configured to determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event. The processing circuitry is configured to determine, one or more features of the cardiac EGM data within the time window. The processing circuitry is configured to compare information relating to the one or more features to one or more corresponding thresholds. The processing circuitry is configured to determine, based on the comparison, whether the event is an oversensing event.

Description

MORPHOLOGY-BASED DETECTION OF OVERSENSING IN MEDICAL DEVICES

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 675,100, filed July 24, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosure relates generally to medical device systems and, more particularly, cardiac monitoring by medical devices.BACKGROUND

[0003] Some types of implantable medical devices, such as cardiac pacemakers or implantable cardioverter defibrillators, provide electrical therapy to a heart of a patient via electrodes of one or more implantable leads. The electrical therapy may be delivered to the heart in the form of pulses for pacing or shocks for cardioversion or defibrillation. In some cases, an implantable medical device may sense the presence arrhythmias of the heart and control the delivery of electrical therapy to the heart based on the sensing. Other medical devices may detect arrhythmias, but do not themselves deliver responsive therapy.SUMMARY

[0003] In general, this disclosure describes example techniques related to determining whether a sensed arrhythmia episode is a true arrhythmia episode or a false arrhythmia episode due to oversensing and, in some examples, controlling the delivery of therapy based on the determination. Oversensing can be a problem with implantable cardiac devices like ICDs. For example, ICDs that use integrated bipolar electrodes, which are more widely separated than traditional short bipole sensing electrodes are more vulnerable to receiving far-field electrical activity (e.g., P-waves) which may lead to oversensing and possible overdetection of arrhythmia episodes. Implantable or external defibrillators and / or monitors including cutaneous, subcutaneous, substernal, and / or extravascular electrodes may be similarly vulnerable to receiving far-field electrical activity. Therefore, it may be desirable to detect oversensing in a detected tachyarrhythmia episode in such devices, especially when detecting on-device (e.g., on the ICD), to avoid delivery of inappropriate therapy.

[0004] In one example, this disclosure describes a system comprising: sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient; and processing circuitry configured to: determine, based on the cardiac EGM data, an occurrence of an event; determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event; determine one or more features of the cardiac EGM data within the time window; compare information relating to the one or more features to one or more corresponding thresholds; and determine, based on the comparison, whether the event is an oversensing event.

[0005] In another example, this disclosure describes a method comprising: sensing, by sensing circuitry, cardiac electrogram (EGM) data of a patient; determining, by processing circuitry and based on the cardiac EGM data, an occurrence of an event; determining, by the processing circuitry and based on the occurrence of the event, a time window of the cardiac EGM data around the event; determining, by the processing circuitry, one or more features of the cardiac EGM data within the time window; comparing, by the processing circuitry, information relating to the one or more features to one or more corresponding thresholds; and determining, by the processing circuitry and based on the comparison, whether the event is an oversensing event.

[0006] In another example, this disclosure describes an implantable medical device comprising: sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient; and processing circuitry configured to: determine, based on the cardiac EGM data, an occurrence of an event; determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event; determine, one or more features of the cardiac EGM data within the time window; compare information relating to the one or more features to one or more corresponding thresholds; and determine, based on the comparison, whether the event is an oversensing event.

[0007] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the methods and systems described in detail within the accompanying drawings and description below. The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below.BRIEF DESCRIPTION OF DRAWINGS

[0008] The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

[0009] FIG. 1 is conceptual diagram illustrating an example medical device system, in accordance with some examples of the current disclosure.

[0010] FIG. 2 is a conceptual diagram further illustrating the implantable medical device (IMD) of FIG. 1, in accordance with some examples of the current disclosure.

[0011] FIG. 3 is a functional block diagram illustrating an example configuration of implantable medical device of FIGS. 1 and 2, in accordance with some examples of the current disclosure.

[0012] FIG. 4 is a conceptual diagram illustrating an example cardiac EGM according to one or more aspects of this disclosure.

[0013] FIG. 5 is a functional block diagram illustrating an example configuration of the external device of the medical system of FIG. 1, in accordance with some examples of the current disclosure.

[0014] FIG. 6 is a block diagram illustrating an example system that includes an external device, such as a server, and one or more computing devices that are coupled to the IMD and external device shown in FIG. 1 via a network, in accordance with some examples of the current disclosure.

[0015] FIG. 7 is a flow diagram illustrating an example technique for morphology -based detection of oversensing according to one or more aspects of this disclosure.

[0016] Like reference characters denote like elements throughout the description and figures.DETAILED DESCRIPTION

[0017] An implantable medical system includes an implantable medical device (IMD), such as a pacemaker, implantable cardioverter defibrillator (ICD), or implantable cardiac resynchronization therapy (CRT) device, that may provide therapies for maintaining and restoring normal cardiac rhythms by pacing and / or by delivering electrical shock therapy for cardioverting or defibrillating the heart. One or more electrical leads connected to the IMD may be inserted into or in proximity to the heart of the patient. The leads carry therapeutic current from the IMD to the heart tissue to either stimulate the heart using low energy pacing pulses or cardiovert / defibrillate the heart using relatively higher energy shocks. The IMD also uses the leads for sensing electrical activity, such as electrogram (EGM) signals, from the heart. Using the EGM signals, the IMD may detect cardiac depolarizations, repolarizations, or other activity, and detect arrhythmias responsive to which the IMD may deliver the electrical therapy. In some examples, within the IMD, sense amplifiers may amplify EGM signals from electrodes on the leads, and the amplified EGM signals may be used by the IMD to sense intrinsic depolarizations of the atria (referred to as P-waves) and the ventricles (referred to as R-waves).

[0018] The implantable medical systems may also include one or more leads that are wholly or partially implanted within the patient and are configured to couple to the HMDs. In some examples, the implantable leads include an integrated bipolar lead, in which an electrode used to deliver relatively higher energy shock therapy, e.g., a coil electrode, serves as either an anode or cathode of a sensing vector, such as a sensing bipole. The sensing bipole of an integrated bipolar lead may have larger (e.g., wider) spacing than a traditional bipolar lead that includes, for example, two relatively more closely spaced electrodes, such as a tip electrode and a ring electrode or two closely spaced ring electrodes. Because of the larger interelectrode spacing, the integrated bipolar lead may capture more of far-field signals. In some examples, an integrated bipolar lead may include a defibrillator coil electrode connected to a ring electrode with the combination of the defibrillator coil electrode and the ring electrode acting as an anode or cathode of a sensing bipole of the integrated bipolar lead. In some examples, integrated bipolar leads may include any lead configured to provide an integrated bipole for sensing, e.g., whether or not the lead is also configured to provide or more traditional bipoles, e.g., includes more closely spaced ring and tip electrodes.

[0019] Integrated bipolar leads that are implanted ventricularly consequently may have a higher chance of atrial oversensing, particularly for integrated bipolar leads that are implanted in the left bundle branch area, septal area, or other location higher up / closer to the atrium than conventional apical implantation. In some examples, a position of an integrated bipolar lead may be adjusted, such as by an implanter, at implant to reduce the chance of a ventricularly-implanted integrated bipolar lead oversensing atrial far-field activity. However, in some cases over time, the ventricularly-implanted integrated bipolar lead may sense atrial far-field activity which may lead to atrial oversensing, e.g., misidentification of features in the EGM associated with atrial depolarizations as ventricular depolarizations. For example, after the leads are implanted, a position of the leads may change, such as due to patient movement, which may cause an increase in sensed atrial far- field activity by an integrated bipolar lead implanted in a ventricle, which can lead to atrial oversensing. Atrial oversensing may lead to a variety of undesired outcomes, such as overdetection of tachyarrhythmias, inhibition of cardiac resynchronization therapy (CRT) and / or loss of optimal AV interval for CRT or other synchronous ventricular pacing.

[0020] Oversensing can be a problem with implantable cardiac devices like ICDs. For example, ICDs with integrated bipolar electrodes more widely separated from each other than traditional short bipole sensing electrodes are more vulnerable to receiving far-field electrical activity (e.g., P-waves) which may lead to oversensing and possible over-detection of arrhythmia episodes. Therefore, it may be desirable to detect oversensing in a detected tachyarrhythmia episode, especially when detecting on-device (e.g., on the ICD), to avoid delivery of inappropriate therapy.

[0021] In general, this disclosure describes example techniques related to morphologybased discrimination of oversensing. Oversensing may cause a medical device or system to detect a false arrhythmia episode. For example, a detected arrhythmia episode may be a true arrhythmia episode or a false arrhythmia episode due to oversensing. This disclosure describes example medical systems, devices, and techniques for determining whether a potential arrhythmia is a true tachyarrhythmia episode or an over-sensed episode.

[0022] For example, the medical device or system may obtain an original sensed signal and apply a high pass filter to the original sensed signal. The medical device or system may determine a characteristic, such as a peak-to-peak amplitude, of the original sensed signal within a predetermined time window and determine the characteristic of the high passfiltered signal within the predetermined time window. The medical device or system may determine a ratio of the characteristics.

[0023] The medical device or system may determine whether an episode is a true tachyarrhythmia or a false tachyarrhythmia based on one or more determined ratios. For example, the medical device or system may compare the ratios to a threshold and look for patterns in results of the comparisons to determine whether an episode is a true tachyarrhythmia or a false tachyarrhythmia.

[0024] FIG. 1 illustrates example medical device system 10 in conjunction with patient 14. Medical device system 10 is an example of a medical device system that is configured to implement the example techniques described herein for morphology-based detection of oversensing. In some examples, medical device system 10 includes an implantable medical device (IMD) 16 in communication with external device 24. In the illustrated example, IMD 16 may be coupled to leads 18, 20, and 22. IMD 16 may be, for example, an implantable cardioverter, an implantable defibrillator, an implantable pacemaker, and / or other implantable medical device that provides electrical signals to heart 12 and senses electrical activity of heart 12 via electrodes coupled to one or more of leads 18, 20, and 22. In some examples, the techniques described herein may be implemented in medical devices that do not deliver therapy, medical devices that are not coupled to their electrodes via leads, and / or medical devices that are not implanted.

[0025] Leads 18, 20, 22 extend into heart 12 of patient 14 to sense electrical activity of heart 12 and to deliver electrical therapy to heart 12. In the example shown in FIG. 1, right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium (RA) 26, and into RV 28. Left ventricular (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of LV 32 of heart 12. Right atrial (RA) lead 22 extends through one or more veins and the vena cava, and into the RA 26 of heart 12. In some examples, IMD 16 may have a different number of leads. For example, IMD 16 may only have lead 18, or may have lead 18 and lead 22.

[0026] In some examples, lead 18 may be referred to as a ventricularly-implanted integrated bipolar lead. In some examples, lead 22 may be referred to as an atrial lead. Although an apical implantation location of lead 18 is illustrated in FIG. 1, ventricularly- implanted integrated bipolar lead 18 may be implanted in other locations in some examples,such as proximate the left bundle branch, ventricular septum, or more generally closer to the right atrium.

[0027] IMD 16 may sense electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes (not shown in FIG. 1) coupled to at least one of the leads 18, 20, 22. In some examples, IMD 16 may also sense electrical signals attendant to the depolarization and repolarization of heart 12 via extravascular electrodes (e.g., electrodes positioned outside the vasculature of patient 14), such as epicardial electrodes, external surface electrodes, subcutaneous electrodes, substernal electrodes, and the like. The configurations of electrodes used by IMD 16 for sensing and pacing may be unipolar or bipolar.

[0028] The natural electrical activation system of a human heart 12 involves several sequential conduction pathways starting with the sino-atrial (SA) node, and continuing through the atrial conduction pathways of Bachmann's bundle and internodal tracts at the atrial level, followed by the atrio-ventricular (AV) node, Common Bundle of His, right and left bundle branches, and a final distribution to the distal myocardial terminals via the Purkinje fiber network. In a normal electrical activation sequence, the cardiac cycle commences with the generation of a depolarization wave at the SA Node in the wall of RA 26. The depolarization wave is transmitted through the atrial conduction pathways of Bachmann's Bundle and the Internodal Tracts at the atrial level into the LA 33 septum. When the atrial depolarization wave has reached the AV node, the atrial septum, and the furthest walls of the right and left atria 26, 33, respectively, the atria 26, 33 may contract as a result of the electrical activation. The aggregate right atrial and left atrial depolarization wave appears as the P-wave of the PQRST complex of a cardiac EGM. When the amplitude of the atrial depolarization wave passing between a pair of unipolar or bipolar pace / sense electrodes located on or adjacent RA 26 and / or LA 33 exceeds a threshold, it is detected as a sensed P-wave. The sensed P-wave may also be referred to as an atrial intrinsic event.

[0029] During or after the atrial contractions, the AV node distributes the depolarization wave inferiorly down the Bundle of His in the intraventricular septum. The depolarization wave may travel to the apical region of heart 12 and then superiorly though the Purkinje Fiber network. The aggregate right ventricular and left ventricular depolarization wave and the subsequent T-wave accompanying re-polarization of the depolarized myocardium may appear as the QRST portion of the PQRST cardiac cycle complex. When the amplitude ofthe QRS ventricular depolarization wave passing between a bipolar or unipolar pace / sense electrode pair located on or adjacent RV 28 and / or LV 32 exceeds a threshold, it is detected as a sensed R-wave. The sensed R-wave may also be referred to as a ventricular intrinsic event, an RV sensing event (RVs), or an LV sensing event (LVs) depending upon the ventricle in which the electrodes of one or more of leads 18, 20, 22 are configured to sense in a particular case.

[0030] In some examples, IMD 16 provides defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 22. Based on signals sensed via one or more of leads 18, 20, 22, e.g., the detection of R-waves, IMD 16 may detect arrhythmia of heart 12, such as fibrillation or other tachyarrhythmia of ventricles 28 and 32, and deliver antitachyarrhythmia therapy to heart 12 in the form of electrical shocks. In some examples, IMD 16 is programmed to deliver a progression of therapies, e.g., shocks with increasing energy levels, until a tachyarrhythmia of heart 12 is stopped. In examples in which IMD 16 provides antitachyarrhythmia shock therapy, IMD 16 may detect tachyarrhythmia by employing any one or more tachyarrhythmia detection techniques known in the art.

[0031] In some examples, external device 24 may be a handheld computing device or a computer workstation. External device 24 may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions. External device 24 can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some examples, a display of external device 24 may include a touch screen display, and a user may interact with external device 24 via the display.

[0032] A user, such as a physician, technician, or other clinician, may interact with external device 24 to communicate with IMD 16. For example, the user may interact with external device 24 to retrieve physiological or diagnostic information from IMD 16. A user may also interact with external device 24 to program IMD 16, e.g., to select values for operational parameters of the IMD 16.

[0033] For example, the user may use external device 24 to retrieve information from IMD 16 regarding the rhythm of heart 12, trends therein over time, or arrhythmia episodes.As another example, the user may use external device 24 to retrieve information from IMD 16 regarding other sensed physiological parameters of patient 14, such as sensed electrical activity, activity, posture, respiration, or thoracic impedance. As another example, the user may use external device 24 to retrieve information from IMD 16 regarding the performance or integrity of IMD 16 or other components of system 10, such as leads 18, 20, and 22, or a power source of IMD 16. In such examples, physiological parameters of patient 14 and data regarding IMD 16 may be stored in a memory of IMD 16 for retrieval by the user. The user may use external device 24 to program parameters of therapy delivery by IMD 16 and / or parameters used for depolarization and / or arrhythmia detection by IMD 16. In some examples, the user may activate certain features of IMD 16 by entering a single command via external device 24, such as depression of a single key or combination of keys of a keypad or a single point-and-select action with a pointing device.

[0034] IMD 16 and external device 24 may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, include inductance modulation, radiofrequency (RF) telemetry, which may be an RF link established via an antenna according to Bluetooth®, WiFi, or medical implant communication service (MICS), though other techniques are also contemplated. In some examples, external device 24 may include a programming head that may be placed proximate to the patient’s body near the IMD 16 implant site in order to improve the quality or security of communication between IMD 16 and external device 24.

[0035] FIG. 2 is a conceptual diagram further illustrating an example configuration of IMD 16 in conjunction with heart 14. In the example of FIG. 2, IMD 16 is coupled to leads 18 and 22. IMD 16 may be coupled to two leads as illustrated in FIG. 2, three leads as illustrated in FIG. 1, or any other numbers of leads. Furthermore, the leads coupled to IMD 16 may be configured differently than those illustrated herein, but IMD 16 may nevertheless implement the techniques of this disclosure.

[0036] As shown in FIG. 2, the proximal ends of leads 18 and 22 are connected to a connector block 34 of IMD 16 to electrically couple the electrodes on the leads to circuitry within the housing 60 of IMD 16. In some examples, proximal ends of leads 18 and 22 may include electrical contacts that electrically couple to respective electrical contacts within connector block 34 of IMD 16. Each of the leads 18 and 22 includes an elongated insulative lead body, which may carry a number of conductors, e.g., a conductor for each electrode onthe lead, each of which may be connected to a respective contact at the proximal end of the lead. Bipolar electrode 42 is located adjacent to a distal end of lead 18 in right ventricle 28. In addition, bipolar electrodes 48 and 50 are located adjacent to a distal end of lead 22 in right atrium 26.

[0037] In some examples, lead 18 may be referred to as a ventricularly-implanted integrated bipolar lead 18 or a ventricular integrated bipolar lead 18. Lead 18 may be configured to facilitate sensing of a ventricular EGM by IMD 16 via an integrated bipolar pair including tip electrode 42 and elongated electrode 62. In some examples, lead 22 may be referred to as an atrial lead 22.

[0038] Electrode 48 may take the form of ring electrodes, and electrodes 42 and 50 may take the form of helix tip electrodes mounted, e.g., with a fixed screw, within insulative electrode heads 52 and 56, respectively. Some helix tip electrodes can include a mechanism for an extendable / retractable helix. In other examples, one or more of electrodes 42 and 50 may take the form of small circular electrodes at the tip of a tined lead or other fixation element. Leads 18 and 22 also include elongated electrodes 62 and 66, respectively, each of which may take the form of a coil, and may be configured for delivery of relatively high energy therapeutic shocks. Each of the electrodes 42, 48, 50, 62 and 66 may be electrically coupled to a respective one of the conductors within the lead body of its associated lead 18 and 22, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads 18 and 22.

[0039] In the example of FIG. 2, IMD 16 includes a housing electrode 58, which may be formed integrally with an outer surface of hermetically-sealed housing 60 of IMD 16, or otherwise coupled to housing 60. In some examples, housing electrode 58 is defined by an uninsulated portion of an outward facing portion of housing 60 of IMD 16. Other division between insulated and uninsulated portions of housing 60 may be employed to define two or more housing electrodes. In some examples, housing electrode 58 comprises substantially all of housing 60.

[0040] IMD 16 may sense electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes 42, 48, 50, 62, and 66. The electrical signals are conducted to IMD 16 from the electrodes via the respective leads 18 and 22. IMD 16 may sense such electrical signals via any bipolar combination of electrodes 40, 42, 48, 50, 62, and 66. For example, IMD 16 may sense a ventricular EGM via an integrated bipolar pairincluding tip electrode 42 and elongated electrode 62. Furthermore, any of the electrodes 42, 48, 50, 62, and 66 may be used for unipolar sensing in combination with housing electrode 58. The combination of electrodes used for sensing may be referred to as a sensing configuration or electrode vector.

[0041] In some examples, IMD 16 delivers pacing pulses via bipolar combinations of electrodes 42, 48, 50, 62, and 66 to produce depolarization of cardiac tissue of heart 12. In some examples, IMD 16 delivers pacing pulses via any of electrodes 42, 48 and 50 in combination with housing electrode 58 in a unipolar configuration. Furthermore, IMD 16 may deliver antitachyarrhythmia shocks, e.g., defibrillation shocks, to heart 12 via any combination of elongated electrodes 62 and 66, and housing electrode 58. IMD 16 may also use electrodes 58, 62, and 66 to deliver cardioversion shocks to heart 12. Electrodes 62 and 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

[0042] The configurations of system 10 illustrated in FIGS. 1 and 2 are merely examples, including the locations of any of the components of system 10. For example, tip electrode 42 of lead 18 may be implanted in a location within the “conduction system” (e.g., the HIS bundle, the HIS bundle area, the right or left bundle area, etc.). In some examples, a system may include extravascular leads and electrodes instead of or in addition to the illustrated transvenous leads 18 and 22. Further, IMD 16 need not be implanted within the patient. In examples in which IMD 16 is not implanted in the patient, IMD 16 may sense electrical signals and / or deliver antitachyarrhythmia shocks and other therapies to heart 12 via percutaneous leads that extend through the skin of a patient to a variety of positions within or outside of heart 12.

[0043] FIG. 3 is a functional block diagram of one example configuration of IMD 16 of FIGS. 1 and 2. In the illustrated example, IMD 16 includes memory 70, processing circuitry 80, sensing circuitry 82, one or more accelerometers 84, therapy delivery circuitry 86, telemetry circuitry 88, and power source 90, one or more of which may be disposed within housing 60 of IMD 16. In some examples, memory 70 includes computer-readable instructions that, when executed by processing circuitry 80, cause IMD 16 and processing circuitry 80 to perform various functions attributed to IMD 16 and processing circuitry 80 herein. Memory 70 may include any volatile, non-volatile, magnetic, optical, or electricalmedia, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media. Sensed physiological parameters of patient 14 (e.g., EGM or electrocardiogram (ECG) signals or atrial events) may be stored by memory 70, e.g., in EGM 74. Memory 70 may also store a counter 72 which may include a count of oversensed events, and threshold(s) 76 which may include any thresholds described herein.

[0044] Processing circuitry 80 may include one or more of a microprocessor, a controller, digital signal processing circuitry (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some examples, processing circuitry 80 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 80 herein may be embodied as software, firmware, hardware or any combination thereof. According to the techniques described herein, processing circuitry 80 may be configured to determine, based on the cardiac EGM data, an occurrence of an event. Processing circuitry 80 may be configured to determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event. Processing circuitry 80 may be configured to determine, one or more features of the cardiac EGM data within the time window. Processing circuitry 80 may be configured to compare information relating to the one or more features to one or more corresponding thresholds. Processing circuitry 80 may be configured to determine, based on the comparison, whether the event is an oversensing event.

[0045] Sensing circuitry 82 is configured to monitor signals from at least one of electrodes 42, 48, 50, 58, 62, or 66 in order to monitor electrical activity of heart 12, e.g., via EGM signals. For example, sensing circuitry 82 may sense atrial intrinsic events (e.g., a P-wave) with electrodes 48, 50, 66 within RA 26. In some examples, sensing circuitry 82 includes switching circuitry to select which of the available electrodes are used to sense the electrical activity of heart 12. For example, processing circuitry 80 may select the electrodes that function as sense electrodes via the switching circuitry within sensing circuitry 82, e.g., by providing signals via a data / address bus. In some examples, sensing circuitry 82 includes one or more sensing channels, each of which may comprise an amplifier. In response to thesignals from processing circuitry 80, the switching circuitry of sensing circuitry 82 may couple the outputs from the selected electrodes to one of the sensing channels.

[0046] In some examples, one channel of sensing circuitry 82 may include an R-wave amplifier that receives signals from selected pairs of electrodes 42, 62, and 58, which are used for pacing and sensing in RV 28 of heart 12. In accordance with the techniques of this disclosure, sensing circuitry 82 may include an R-wave amplifier that receives a signal from an integrated bipolar pair of electrodes 42 and 62, i.e., an integrated bipolar ventricular EGM signal, and detects R- waves within the signal. In some examples, the R-wave amplifiers may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm. In accordance with the techniques of this disclosure, processing circuitry 80 may adjust a parameter of the adjustable sensing threshold, e.g., to increase the threshold and make the threshold less sensitive to waves in the integrated bipolar ventricular EGM signal, in response to a windowed portion of the integrated bipolar ventricular EGM signal satisfying a far-field activity threshold. As used herein something may satisfy a threshold by a value or property of the something being one of greater than, greater than or equal to, less than, or less than or equal to, depending on the circumstances.

[0047] In addition, in some examples, one channel of sensing circuitry 82 may include a P-wave amplifier that receives signals from electrodes 48 and 50, which are used for pacing and sensing in RA26 of heart 12. In some examples, the P-wave amplifier may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in U.S. Patent No. 5,117,824 to Keimel et al., which issued on June 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of sensing circuitry 82 may be selectively coupled to housing electrode 58, or elongated electrodes 62, or 66, with or instead of one or more of electrodes 42, 48 or 50, e.g., for unipolar or integrated bipolar sensing of R-waves or P-waves in any of chambers 26, 28, or 32 of heart 12.

[0048] In some examples, sensing circuitry 82 includes a channel that comprises an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers. Signalsfrom the selected sensing electrodes that are selected for coupling to this wide-band amplifier may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in memory 70 as an EGM. In some examples, the storage of such EGMs in memory 70 may be under the control of a direct memory access circuit. Processing circuitry 80 may employ digital signal analysis techniques to characterize the digitized signals stored in memory 70 to detect and classify the patient's heart rhythm from the electrical signals. Processing circuitry 80 may detect and classify the heart rhythm of patient 14 by employing any of the numerous signal processing methodologies known in the art. In some examples, sensing 82 stores the integrated bipolar EGM, e.g., the ventricular integrated bipolar EGM, in memory 70 for windowing and further processing by processing circuitry 80 in accordance with the techniques of this disclosure.

[0049] Signals generated by sensing circuitry 82 may include, for example: an RA-event signal, which indicates a detection of a P-wave via electrodes implanted within RA 26 (FIG. 1); a left atrium (LA)-event signal, which indicates a detection of a P-wave via electrodes implanted within LA 33 (FIG. 1); an RV-event signal, which indicates a detection of an R- wave via electrodes implanted within RV 28; or an LV-event signal, which indicates a detection of an R-wave via electrodes implanted within LV 32.

[0050] In some examples, IMD 16 may include one or more additional sensors, such as accelerometers 84. In some examples, accelerometers 84 may comprise one or more three- axis accelerometers. Signals generated by accelerometers 84 may be indicative of, for example, gross body movement of patient 14, such as a patient posture or activity level. Regardless of the configuration of accelerometers 84, processing circuitry 80 may determine patient parameter values based on the signals obtained therefrom. Accelerometers 84 may produce and provide signals to processing circuitry 80 for a determination as to the posture and activity level of patient 14 at a given time. Processing circuitry 80 may then use the determined posture and activity level to further determine whether patient 14 is awake or asleep, and, if patient 14 is determined to be awake, to further determine whether patient 14 is at rest or exercising.

[0051] Therapy delivery circuitry 86 is electrically coupled to electrodes 42, 48, 50, 58, 62, and 66, e.g., via conductors of the respective lead 18, 20, 22, or, in the case of housingelectrode 58, via an electrical conductor disposed within housing 60 of IMD 16. Therapy delivery circuitry 86 is configured to generate and deliver electrical therapy.

[0052] In some examples, therapy delivery circuitry 86 is configured to deliver cardioversion or defibrillation shocks to heart 12. The pacing stimuli, cardioversion shocks, and defibrillation shocks may be in the form of pulses. In other examples, therapy delivery circuitry 86 may deliver one or more of these types of therapy in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

[0053] Therapy delivery circuitry 86 may include a switching circuitry, and processing circuitry 80 may use the switching circuitry to select, e.g., via a data / address bus, which of the available electrodes are used to deliver shock pulses or pacing pulses. The switching circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple therapeutic energy to selected electrodes. In other examples, processing circuitry 80 may select a subset of electrodes 42, 48, 50, 58, 62, and 66 with which therapy is delivered to heart 12 without a switching circuitry.

[0054] Processing circuitry 80 may include pacer timing and control circuitry, which may be embodied as hardware, firmware, software, or any combination thereof. Pacer timing and control circuitry may comprise a dedicated hardware circuit, such as an ASIC, separate from other processing circuitry 80 components, such as one or more microprocessors, or a software module executed by a component of processing circuitry 80 (e.g., one or more microprocessors and / or ASICs).

[0055] In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms. In one example, processing circuitry 80 may utilize all or a subset of the rule-based detection methods described in U.S. Patent No. 5,545,182 to Olson et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on August 13, 1996, or in U.S. Patent No. 5,755,736 to Gillberg et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on May 26, 1998. U.S. Patent No. 5,545,182 to Olson et al. and U.S. Patent No. 5,755,736 to Gillberg et al. are incorporated herein by reference in their entireties. However, other arrhythmia detection methodologies may also be employed by processing circuitry 80 in other examples.

[0056] In some examples, processing circuitry 80 may employ an M of N rule based technique for determining a suspected arrhythmia. For example, if processing circuitry 80 detects at least M fast beats within N consecutive beats, processing circuitry 80 may determine that there is a suspected arrhythmia episode within the N consecutive beats. A fast beat may be a beat having a sensed interval from a last beat (e.g., a sensed ventricular event from a last sensed ventricular event) of a period less than (or less than or equal to) a threshold time, for example, less than 140ms.

[0057] Each fast beat within the N consecutive beats may be considered an event, such that all of the fast beats within the N consecutive beats make up or are part of the suspected arrhythmia episode. When determining whether a suspected arrhythmia episode is a true arrhythmia episode or a false arrhythmia episode due to oversensing as described herein, in some examples, processing circuitry 80 may ignore the non-fast beats occurring within the suspected arrhythmia episode. The values of M and / or N may be programmable. In some examples, M may equal 30 and N may equal 40.

[0058] If IMD 16 is configured to generate and deliver defibrillation shocks to heart 12, therapy delivery circuitry 86 may include a high voltage charge circuit and a high voltage output circuit. In the event that processing circuitry 80 determines that generation of a cardioversion or defibrillation shock is required, processing circuitry 80 may employ the escape interval counter to control timing of such cardioversion and defibrillation shocks, as well as associated refractory periods. In response to the detection of atrial or ventricular fibrillation or tachyarrhythmia requiring a cardioversion pulse, processing circuitry 80 may activate a cardioversion / defibrillation control circuitry (not shown), which may be a hardware component of processing circuitry 80 and / or a firmware or software module executed by one or more hardware components of processing circuitry 80. The cardioversion / defibrillation control circuitry may initiate charging of the high voltage capacitors of the high voltage charge circuit of therapy delivery circuitry 86 under control of a high voltage charging control line.

[0059] Processing circuitry 80 may monitor the voltage on the high voltage capacitor, e.g., via a voltage charging and potential (VCAP) line. In response to the voltage on the high voltage capacitor reaching a predetermined value set by processing circuitry 80, processing circuitry 80 may generate a logic signal that terminates charging. Thereafter, timing of the delivery of the defibrillation or cardioversion pulse by therapy deliverycircuitry 86 is controlled by a cardioversion / defibrillation control circuitry (not shown) of processing circuitry 80. Following delivery of the fibrillation or tachycardia therapy, processing circuitry 80 may return therapy delivery circuitry 86 to a cardiac pacing function and await the next successive interrupt due to pacing or the occurrence of a sensed atrial or ventricular depolarization.

[0060] Therapy delivery circuitry 86 may deliver cardioversion or defibrillation shock with the aid of an output circuit that determines whether a monophasic or biphasic pulse is delivered, whether housing electrode 58 serves as cathode or anode, and which electrodes are involved in delivery of the cardioversion or defibrillation pulses. Such functionality may be provided by one or more switches or a switching circuitry of therapy delivery circuitry 86.

[0061] Telemetry circuitry 88 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 24 (FIG. 1). Under the control of processing circuitry 80, telemetry circuitry 88 may receive downlink telemetry from and send uplink telemetry to external device 24 with the aid of an antenna, which may be internal and / or external. Processing circuitry 80 may provide the data to be uplinked to external device 24 and the control signals for the telemetry circuit within telemetry circuitry 88, e.g., via an address / data bus. In some examples, telemetry circuitry 88 may provide received data to processing circuitry 80 via a multiplexer. In some examples, processing circuitry 80 may transmit atrial and / or ventricular heart signals (e.g., EGM signals) produced by atrial and / or ventricular sense amplifier circuits within sensing circuitry 82 to external device 24.

[0062] Telemetry circuitry 88 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 24 (FIG. 1). Under the control of processing circuitry 80, telemetry circuitry 88 may receive downlink telemetry from and send uplink telemetry to external device 24 with the aid of an antenna, which may be internal and / or external. Processing circuitry 80 may provide the data to be uplinked to external device 24 and the control signals for the telemetry circuit within telemetry circuitry 88, e.g., via an address / data bus. In some examples, telemetry circuitry 88 may provide received data to processing circuitry 80 via a multiplexer.

[0063] The various components of IMD 16 are coupled to power source 90, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may beselected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

[0064] IMD 16 may detect oversensed events and store a count of such events, e.g., in counter 72. If the count exceeds a threshold, the medical device or system may send an alert for possible reprogramming of the sensitivity of the sensing to prevent frequent oversensing.

[0065] Morphologic features of true sensed ventricular activation may be different than those arising out of other electrical activity (e.g., far-field atrial depolarization, ventricular repolarization, non-cardiac electrical noise, etc.). Morphologic features such as peak to peak amplitude, maximum and minimum slew rate, maximum amplitude, minimum amplitude may be used to detect far-field oversensing from integrated bipolar leads. For example, far- field electrical activity, such as P-waves or T-waves or non-cardiac electrical signals (e.g., noise) may have different features than a true sensed ventricular electrical activation. For example, processing circuitry 80 may generate a time window of a predetermined length (e.g., 150ms - 250ms) around a sensed event. Processing circuitry 80 may evaluate EGM features within the time window. Processing circuitry 80 may determine a sensed event to be an oversensing event if greater than or equal to N of the following criteria are true. N can be a number such as 3, 4, 5, 6, etc.

[0066] The criteria may include: 1) The absolute maximum amplitude of the EGM within the window is less than (or less than or equal to) a predetermined threshold OR the absolute minimum amplitude of the EGM within the window is less than (or less than or equal to) a predetermined threshold; 2) The peak to peak amplitude of the EGM within the window is less than (or less than or equal to) a predetermined threshold; 3) The magnitude of maximum slew rate of the EGM within the window is less than (or less than or equal to) a predetermined threshold; 4) The magnitude of the minimum slew rate of the EGM within the window is less than (or less than or equal to) a predetermined threshold; 5) The magnitude of signal amplitude at the maximum slew rate of the EGM within the window is less than (or less than or equal to) a predetermined threshold; and / or 6) The magnitude of signal amplitude at the minimum slew rate of the EGM within the window is less than (or less than or equal to) a predetermined threshold.

[0067] In some examples, processing circuitry 80 may determine the above EGM features of a vector that is different from the sensing vector. In some examples, this different or alternative vector may be referred to as an EGM morphology vector. In some examples,the alternative vector may be lead tip-can or atrial ring-can, if atrial lead 22 is present. For example, for a single chamber ICD, a sensing vector may be acquired from an RV tip to RV coil or from RV tip to RV ring, and the alternative, EGM morphology vector may be acquired from RV coil to can. In some examples, processing circuitry 80 may determine a ratio of such features taken from the sensing vector to those taken from the different (e.g., alternative) vector. If a ratio of certain feature(s) (e.g., maximum amplitude, minimum amplitude, peak to peak amplitude, etc.) exceeds (or exceeds or equals) a predetermined threshold, processing circuitry 80 may determine the sensing event to be oversensing.

[0068] Some IMDs may include sensors that do not directly measure electrical activity of the heart. Such sensors may include one or more microphone(s) 85 which may be used to determine heart activity. Such sensors may not be affected by far-field electrical activity like P-waves and T-waves and may be able to be used to cross-check a heart rate in the case of oversensed tachyarrhythmia episodes. As such, processing circuitry 80 may cross-check a ventricular rate with an independent sensor, such as microphone(s) 85.

[0069] For example, when processing circuitry 80 determines fast heart beats, processing circuitry 80 may turn on a sensor channel (e.g., for microphone(s) 85) to detect and record the beats. The sensor channel may include heart sounds, for example, captured by microphone(s) 85. Processing circuitry 80 may detect the SI component of the heart sound using a relatively high threshold for sensing or a high sensitivity floor so that noise or other components of heart sounds are not sensed. The SI component of heart sounds is the sound made by the closure of the atrioventricular valves when ventricular pressures exceed atrial pressures at the beginning of systole. Processing circuitry 80 may determine a heart rate from the interval between two successive S 1 components. If the heart rate detected from the heart sounds is within a normal range (e.g., within a threshold range), processing circuitry 80 may flag the electrically sensed (e.g., via EGM) tachyarrhythmia episode as an oversensed episode and prevent (e.g., withhold) delivery of therapy. In some examples, the normal range may be between 50 bpm and 100 bpm. In some examples, rather than, or in addition to using microphone(s) 85 to determine the heart rate, the medical device or system may use a bioimpedance (BioZ) sensor (e.g., of sensing circuitry 82).

[0070] FIG. 4 is a conceptual diagram illustrating an example cardiac EGM according to one or more aspects of this disclosure. In the example of FIG. 4, EGM 400 include event 404. For example, IMD 16 may determine the occurrence of event 404. IMD 16 maydetermine time window 402 around event 404. IMD 16 may use time window 402 to determine one or more features of 400 which occur within time window 402. IMD 16 may compare such features to corresponding thresholds to determine whether event 404 is an oversensing event.

[0071] FIG. 5 is functional block diagram of an example external device 24. As shown in FIG. 5, external device 24 includes processing circuitry 100, a memory 102, a user interface 104, telemetry circuitry 106, and a power source 108. External device 24 may be a dedicated hardware device with dedicated software for interacting with IMD 16. Alternatively, external device 24 may be an off-the-shelf computing device running an application that enables external device 24 to interact with IMD 16.

[0072] A user may use external device 24 to select programmable parameters that control the monitoring and delivery of therapy by IMD 16, and to retrieve information collected by IMD regarding the condition of patient 14 or the performance of IMD 16. The user may interact with external device 24 via user interface 104, which may include display to present graphical user interface to a user, and a keypad or another mechanism for receiving input from a user.

[0073] Processing circuitry 100 can take the form one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed to processing circuitry 100 herein may be embodied as hardware, firmware, software or any combination thereof. Memory 102 may store instructions that cause processing circuitry 100 to provide the functionality ascribed to external device 24 herein, and information used by processing circuitry 100 to provide the functionality ascribed to external device 24 herein. Memory 102 may include one or more of any fixed or removable magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like. Memory 102 may also include one or more removable memory portions that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow patient data to be easily transferred to another computing device, or to be removed before external device 24 is used to program therapy for another patient. Memory 102 may also store information that controls therapy delivery by IMD 16, such as stimulation parameter values.

[0074] External device 24 may communicate wirelessly with IMD 16, such as using RF communication or proximal inductive interaction. This wireless communication is possiblethrough the use of telemetry circuitry 106, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled to external device 24 may correspond to the programming head that may be placed over heart 12, as described above with reference to FIG. 1.

[0075] Telemetry circuitry 106 may be similar to telemetry circuitry 88 of IMD 16 (FIG. 3). Telemetry circuitry 106 may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. Examples of local wireless communication techniques that may be employed to facilitate communication between external device 24 and another computing device include RF communication according to the 802.11 or Bluetooth specification sets, infrared communication, e.g., according to the IrDA standard, or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating with external device 24 without needing to establish a secure wireless connection.

[0076] Power source 108 is configured to deliver operating power to the components of external device 24. Power source 108 may include a battery and a power generation circuit to produce the operating power. In some embodiments, the battery may be rechargeable to allow extended operation. Recharging may be accomplished by electrically coupling power source 108 to a cradle or plug that is connected to an alternating current (AC) outlet. In addition or alternatively, recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within external device 24. In other embodiments, traditional batteries (e.g., nickel cadmium or lithium ion batteries) may be used. In addition, external device 24 may be directly coupled to an alternating current outlet to power external device 24. Power source 108 may include circuitry to monitor power remaining within a battery. In this manner, user interface 104 may provide a current battery level indicator or low battery level indicator when the battery needs to be replaced or recharged. In some cases, power source 108 may be capable of estimating the remaining time of operation using the current battery.

[0077] In some examples, processing circuitry 100 and memory 102 of external device 24 may be configured to provide some or all of the functionality ascribed to processing circuitry 80 and memory 70 of IMD 16. In some examples, processing circuitry 100 maybe configured to perform one or more of the techniques as described herein with respect to processing circuitry 80 of IMD 16.

[0078] FIG. 6 is a block diagram illustrating a system 110 that includes an external device 112, such as a server, and one or more computing devices 114A-114N that are coupled to IMD 16 and external device 24 shown in FIG. 1 via a network 120, according to one example. In this example, IMD 16 uses telemetry circuitry 88 (FIG. 3) to communicate with external device 24 via a first wireless connection, and to communicate with an access point 122 via a second wireless connection. In the example of FIG. 6, access point 122, external device 24, external device 112, and computing devices 114A-114N are interconnected, and able to communicate with each other, through network 120. In some cases, one or more of access point 122, external device 24, external device 112, and computing devices 114A-114N may be coupled to network 120 through one or more wireless connections. IMD 16, external device 24, external device 112, and computing devices 114A-114N may each comprise one or more processing circuitries, such as one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, that may perform various functions and operations, such as those described herein.

[0079] Access point 122 may comprise a device that connects to network 120 via any of a variety of connections, such as telephone dial-up, digital subscriber line (DSL), or cable modem connections. In other examples, access point 122 may be coupled to network 120 through different forms of connections, including wired or wireless connections. In some examples, access point 122 may communicate with external device 24 and / or IMD 16. Access point 122 may be co-located with patient 14 (e.g., within the same room or within the same site as patient 14) or may be remotely located from patient 14. For example, access point 122 may be a home monitor that is located in the patient’s home or is portable for carrying with patient 14.

[0080] During operation, IMD 16 may collect, measure, and store various forms of diagnostic data. For example, as described previously, IMD 16 may collect EGM signals, generate a time window of an integrated bipolar EGM signal, determine values of one or more features of the integrated bipolar EGM signal during the time window, and adjust a sensitivity threshold used to detect R-waves or other near field depolarizations. In certain cases, IMD 16 may directly analyze collected diagnostic data and generate any corresponding reports or alerts. In some cases, however, IMD 16 may send diagnostic datato external device 24, access point 122, and / or external device 112, either wirelessly or via access point 122 and network 120, for remote processing and analysis.

[0081] IMD 16 may provide external device 112 with collected EGM data, system integrity indications, and any other relevant physiological or system data via access point 122 and network 120. External device 112 includes one or more processing circuitries 118. In some cases, external device 112 may request such data, and in some cases, IMD 16 may automatically or periodically provide such data to external device 112. Upon receipt of the diagnostic data via input / output device 116, external device 112 is capable of analyzing the data and generating reports or alerts upon determination that there may be a possible condition with one or more of leads 18, 20, and 22, or with patient 14.

[0082] In one example, external device 112 may comprise a secure storage site for information that has been collected from IMD 16 and / or external device 24. In this example, network 120 may comprise an Internet network; and trained professionals, such as clinicians, may use computing devices 114A-114N to securely access stored data on external device 112. For example, the trained professionals may need to enter usernames and passwords to access the stored information on external device 112. In one embodiment, external device 112 may be a CareLink™ server provided by Medtronic, Inc., of Minneapolis, Minnesota.

[0083] In some examples, processing circuitry and memory of one or more of access point 122, server 112, or computing devices 114, e.g., processing circuitry 118 and memory of server 112, may be configured to provide some or all of the functionality ascribed to processing circuitry 80 and memory 70 of IMD 16. In some examples, processing circuitry 118 may be configured to perform one or more of the techniques described herein as attributed to processing circuitry 80.

[0084] FIG. 7 is a flow diagram illustrating an example technique for morphology -based detection of oversensing according to one or more aspects of this disclosure. Sensing circuitry 82 may sense a cardiac electrogram (EGM) data of a patient. Processing circuitry 80 may determine, based on the cardiac EGM data, an occurrence of an event (700). For example, processing circuitry 80 may detect an event in the cardiac EGM data. Processing circuitry 80 may determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event (702). For example, processing circuitry 80 may determine a window around the event.

[0085] Processing circuitry 80 may determine, one or more features of the cardiac EGM data within the time window (704). For example, processing circuitry 80 may determine at least one of an absolute maximum amplitude, an absolute minimum amplitude, a peak-to- peak amplitude, a maximum slew rate, a minimum slew rate, a signal amplitude at the maximum slew rate, or a signal amplitude at the minimum slew rate within the time window. Processing circuitry 80 may compare information relating to the one or more features to one or more corresponding thresholds (706). For example, processing circuitry 80 may compare each of the one or more features to a corresponding threshold. In some examples, the information relating to the one or more features includes information from a current sensed event. In some examples, the information relating to the one or more features includes information from a current sensed event and a previous sensed event. For example, processing circuitry 80 may compare a ratio of the amplitude of the current sensed event (e.g., an R-wave) to the amplitude of the previously sensed event (e.g., a P-wave) (or vice versa) to a threshold.

[0086] Processing circuitry 80 may determine, based on the comparison, whether the event is an oversensing event (708). For example, the one or more features may include a plurality of features and processing circuitry 80 may determine whether N of M of the plurality of features satisfy the one or more corresponding thresholds.

[0087] In some examples, the event is an oversensing event and processing circuitry 80 may increment, based on determining the event is an oversensing event, a counter of oversensing events. In some examples, processing circuitry 80 may compare the count of oversensing events to an oversensing event threshold. In some examples, processing circuitry 80 may send, based on the count of oversensing events satisfying the oversensing event threshold and to an external device, an indication that the count satisfies the oversensing event threshold. In some examples, the indication includes an alert with an instruction to change a sensitivity of the sensing circuitry.

[0088] In some examples, the one or more features include a plurality of features, and to determine whether the event is a true event, processing circuitry 80 may to determine whether N of M of the plurality of features satisfy the one or more corresponding thresholds.

[0089] In some examples, the one or more features comprise at least one of: an absolute maximum amplitude, an absolute minimum amplitude, a peak-to-peak amplitude, a maximum slew rate, a minimum slew rate, a signal amplitude at the maximum slew rate, ora signal amplitude at the minimum slew rate. In some examples, the event is a current event and processing circuitry 80 may alter at least one of the corresponding thresholds based on one or more events occurring prior to the current event. In some examples, the information relating to the one or more features includes the one or more features.

[0090] In some examples, the cardiac EGM data comprises a first cardiac EGM sensed via a first sensing vector and a second cardiac EGM sensed via a second sensing vector, the first sensing vector being different than the second sensing vector. In some examples, processing circuitry 80 may determine the occurrence of the event is based on the first cardiac EGM. In some examples, the time window is a time window in the first cardiac EGM and the second cardiac EGM. In some examples, the information associated with the one or more features comprises a corresponding ratio of each of the one or more features in the first cardiac EGM to each corresponding feature in the second cardiac EGM.

[0091] In some examples, HMD 16 further includes one or more sensors configured to sense heart sounds (e.g., microphone(s) 85). In some examples, the event is an oversensing event. In some examples, processing circuitry 80 may determine a first SI component of the heart sounds. Processing circuitry 80 may determine a second SI component of the heart sounds. Processing circuitry 80 may determine a heart rate based on a time interval between the first SI and the second SI. Processing circuitry 80 may determine that the heart rate is within a predetermined range. Processing circuitry 80 may determine, based on determining that the heart rate is within the predetermined range, that an episode associated with the event is an oversensed episode. In some examples, processing circuitry 80 may withhold, based on the determination that the episode is an oversensed episode, delivery of therapy to the patient. In some examples, the predetermined range comprises between 50 beats per minute and 100 beats per minute.

[0092] In some examples, the heart rate is a first heart rate. In some examples, the sensing circuitry is further configured to sense a bio impedance of the patient. In some examples, processing circuitry may determine, based on the sensed bio impedance, a second heart rate. IN some examples, processing circuitry 80 may determine that the heart rate is within the predetermined range, is based on the first heart rate and the second heart rate.

[0093] In some examples, the time window has a duration of between 150 milliseconds and 250 milliseconds. In some examples, the system includes an implantable medical device including the sensing circuitry. In some examples, implantable medical device comprisesan implantable cardioverter defibrillator. In some examples, a system includes an integrated bipolar lead coupled to the implantable cardioverter defibrillator, and the sensing circuitry is configured to sense the EGM via the integrated bipolar lead.

[0094] In one or more examples, the functions described in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on, as one or more instructions or code, a computer- readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media forming a tangible, non-transitory medium. Instructions may be executed by one or more processing circuitries, such as one or more DSPs, ASICs, FPGAs, general purpose microprocessors, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processing circuitry,” as used herein may refer to one or more of any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.

[0095] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuitry, as well as any combinations of such components, embodied in external devices, such as physician or patient programmers, stimulators, or other devices. The terms “processor” and “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry, and alone or in combination with other digital or analog circuitry.

[0096] For aspects implemented in software, at least some of the functionality ascribed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

[0097] In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or unitsmay be performed by separate hardware or software components, or integrated within common or separate hardware or software components. Also, the techniques could be fully implemented in one or more circuits or logic elements. The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including an IMD, an external programmer, a combination of an IMD and external programmer, an integrated circuit (IC) or a set of ICs, and / or discrete electrical circuitry, residing in an IMD and / or external programmer.

[0098] Various aspects of the techniques may enable the following examples.

[0099] Example 1. A system comprising: sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient; and processing circuitry configured to: determine, based on the cardiac EGM data, an occurrence of an event; determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event; determine one or more features of the cardiac EGM data within the time window; compare information relating to the one or more features to one or more corresponding thresholds; and determine, based on the comparison, whether the event is an oversensing event.

[0100] Example 2. The system of example 1, wherein the event is an oversensing event and wherein the processing circuitry is further configured to increment, based on determining the event is an oversensing event, a counter of oversensing events.

[0101] Example 3. The system of example 2, wherein the processing circuitry is further configured to: compare the count of oversensing events to an oversensing event threshold; and send, based on the count of oversensing events satisfying the oversensing event threshold and to an external device, an indication that the count satisfies the oversensing event threshold.

[0102] Example 4. The system of example 3, wherein the indication comprises an alert with an instruction to change a sensitivity of the sensing circuitry.

[0103] Example 5. The system of any of examples 1-4, wherein the one or more features comprise a plurality of features, and wherein to determine whether the event is a true event, the processing circuitry is configured to determine whether N of M of the plurality of features satisfy the one or more corresponding thresholds.

[0104] Example 6. The system of any of examples 1-5, wherein the one or more features comprise at least one of: an absolute maximum amplitude, an absolute minimumamplitude, a peak-to-peak amplitude, a maximum slew rate, a minimum slew rate, a signal amplitude at the maximum slew rate, or a signal amplitude at the minimum slew rate.

[0105] Example 7. The system of any of examples 1-6, wherein the event is a current event and the processing circuitry is further configured to alter at least one of the corresponding thresholds based on one or more events occurring prior to the current event.

[0106] Example 8. The system of any of examples 1-7, wherein the information relating to the one or more features comprises the one or more features.

[0107] Example 9. The system of any of examples 1-7, wherein the cardiac EGM data comprises a first cardiac EGM sensed via a first sensing vector and a second cardiac EGM sensed via a second sensing vector, the first sensing vector being different than the second sensing vector, wherein determining the occurrence of the event is based on the first cardiac EGM, wherein the time window is a time window in the first cardiac EGM and the second cardiac EGM, and wherein the information associated with the one or more features comprises a corresponding ratio of each of the one or more features in the first cardiac EGM to each corresponding feature in the second cardiac EGM.

[0108] Example 10. The system of any of examples 1-9, wherein the system further comprises one or more sensors configured to sense heart sounds, wherein the event is an oversensing event, and wherein the processing circuitry is further configured to: determine a first SI component of the heart sounds; determine a second SI component of the heart sounds; determine a heart rate based on a time interval between the first SI and the second SI; determine that the heart rate is within a predetermined range; and determine, based on determining that the heart rate is within the predetermined range, that an episode associated with the event is an oversensed episode.

[0109] Example 11. The system of example 10, wherein the processing circuitry is further configured to withhold, based on the determination that the episode is an oversensed episode, delivery of therapy to the patient.

[0110] Example 12. The system of example 10 or example 11, wherein the predetermined range comprises between 50 beats per minute and 100 beats per minute.

[0111] Example 13. The system of any of examples 10-12, wherein the heart rate is a first heart rate, and wherein the sensing circuitry is further configured to: sense a bio impedance of the patient; and determine, based on the sensed bio impedance, a secondheart rate, wherein determining that the heart rate is within the predetermined range, is based on the first heart rate and the second heart rate.

[0112] Example 14. The system of any of examples 1-13, wherein the time window has a duration of between 150 milliseconds and 250 milliseconds.

[0113] Example 15. The system of any of examples 1-14, further comprising an implantable medical device comprising the sensing circuitry.

[0114] Example 16. The system of example 15, wherein the implantable medical device comprises an implantable cardioverter defibrillator.

[0115] Example 17. The system of example 16, further comprising an integrated bipolar lead coupled to the implantable cardioverter defibrillator, wherein the sensing circuitry is configured to sense the EGM via the integrated bipolar lead.

[0116] Example 18. A method comprising: sensing, by sensing circuitry, cardiac electrogram (EGM) data of a patient; determining, by processing circuitry and based on the cardiac EGM data, an occurrence of an event; determining, by the processing circuitry and based on the occurrence of the event, a time window of the cardiac EGM data around the event; determining, by the processing circuitry, one or more features of the cardiac EGM data within the time window; comparing, by the processing circuitry, information relating to the one or more features to one or more corresponding thresholds; and determining, by the processing circuitry and based on the comparison, whether the event is an oversensing event.

[0117] Example 19. The method of example 18, wherein the one or more features comprise a plurality of features, and wherein determining whether the event is a true event comprises determining whether N of M of the plurality of features satisfy the one or more corresponding thresholds.

[0118] Example 20. An implantable medical device comprising: sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient; and processing circuitry configured to: determine, based on the cardiac EGM data, an occurrence of an event; determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event; determine, one or more features of the cardiac EGM data within the time window; compare information relating to the one or more features to one or more corresponding thresholds; and determine, based on the comparison, whether the event is an oversensing event.

[0119] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

CLAIMS:

1. A system comprising: sensing circuitry configured to sense cardiac electrogram (EGM) data of a patient; and processing circuitry configured to: determine, based on the cardiac EGM data, an occurrence of an event; determine, based on the occurrence of the event, a time window of the cardiac EGM data around the event; determine one or more features of the cardiac EGM data within the time window; compare information relating to the one or more features to one or more corresponding thresholds; and determine, based on the comparison, whether the event is an oversensing event.

2. The system of claim 1, wherein the event is an oversensing event and wherein the processing circuitry is further configured to increment, based on determining the event is an oversensing event, a counter of oversensing events.

3. The system of claim 2, wherein the processing circuitry is further configured to: compare the count of oversensing events to an oversensing event threshold; and send, based on the count of oversensing events satisfying the oversensing event threshold and to an external device, an indication that the count satisfies the oversensing event threshold.

4. The system of claim 3, wherein the indication comprises an alert with an instruction to change a sensitivity of the sensing circuitry.

5. The system of any of claims 1-4, wherein the one or more features comprise a plurality of features, and wherein to determine whether the event is a true event, theprocessing circuitry is configured to determine whether N of M of the plurality of features satisfy the one or more corresponding thresholds.

6. The system of any of claims 1-5, wherein the one or more features comprise at least one of an absolute maximum amplitude, an absolute minimum amplitude, a peak-to- peak amplitude, a maximum slew rate, a minimum slew rate, a signal amplitude at the maximum slew rate, or a signal amplitude at the minimum slew rate.

7. The system of any of claims 1-6, wherein the event is a current event and the processing circuitry is further configured to alter at least one of the corresponding thresholds based on one or more events occurring prior to the current event.

8. The system of any of claims 1-7, wherein the information relating to the one or more features comprises the one or more features.

9. The system of any of claims 1-7, wherein the cardiac EGM data comprises a first cardiac EGM sensed via a first sensing vector and a second cardiac EGM sensed via a second sensing vector, the first sensing vector being different than the second sensing vector, wherein determining the occurrence of the event is based on the first cardiac EGM, wherein the time window is a time window in the first cardiac EGM and the second cardiac EGM, and wherein the information associated with the one or more features comprises a corresponding ratio of each of the one or more features in the first cardiac EGM to each corresponding feature in the second cardiac EGM.

10. The system of any of claims 1-9, wherein the system further comprises one or more sensors configured to sense heart sounds, wherein the event is an oversensing event, and wherein the processing circuitry is further configured to: determine a first SI component of the heart sounds; determine a second S 1 component of the heart sounds; determine a heart rate based on a time interval between the first SI and the second Si; determine that the heart rate is within a predetermined range; anddetermine, based on determining that the heart rate is within the predetermined range, that an episode associated with the event is an oversensed episode.

11. The system of claim 10, wherein the processing circuitry is further configured to withhold, based on the determination that the episode is an oversensed episode, delivery of therapy to the patient.

12. The system of claim 10 or claim 11, wherein the predetermined range comprises between 50 beats per minute and 100 beats per minute.

13. The system of any of claims 10-12, wherein the heart rate is a first heart rate, and wherein the sensing circuitry is further configured to: sense a bio impedance of the patient; and determine, based on the sensed bio impedance, a second heart rate, wherein determining that the heart rate is within the predetermined range, is based on the first heart rate and the second heart rate.

14. The system of any of claims 1-13, wherein the time window has a duration of between 150 milliseconds and 250 milliseconds.

15. A method comprising: sensing, by sensing circuitry, cardiac electrogram (EGM) data of a patient; determining, by processing circuitry and based on the cardiac EGM data, an occurrence of an event; determining, by the processing circuitry and based on the occurrence of the event, a time window of the cardiac EGM data around the event; determining, by the processing circuitry, one or more features of the cardiac EGM data within the time window; comparing, by the processing circuitry, information relating to the one or more features to one or more corresponding thresholds; and determining, by the processing circuitry and based on the comparison, whether the event is an oversensing event.

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