Identifying false tachyarrhythmia episodes based on respiration

Abstract

An implantable medical device comprises sensing circuitry configured to: sense, via one or more electrodes of a plurality of electrodes, a cardiac electrogram (EGM) of a patient; and sense a physiological signal indicative of respiration of the patient; and processing circuitry configured to: identify a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on the physiological signal indicative of respiration of the patient, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

Description

Atly Ref. No. A0012803 WOO 1IDENTIFYING FALSE TACHYARRHYTHMIA EPISODES BASED ON RESPIRATION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 708,366, filed October 17, 2024, the entire content of which is incorporated herein by reference.FIELD

[0002] This disclosure generally relates to cardiac device systems, such as an implantable cardiac device system configured to deliver anti -tachyarrhythmia therapy.BACKGROUND

[0003] For patients at risk of tachyarrhythmias, such as ventricular fibrillation (VF) and / or non-perfusing ventricular tachycardia (VT), an implantable cardiac device system, such as an implantable cardioverter defibrillator (ICD) system, may be used to delivery anti-tachyarrhythmia therapy to a heart of the patient. An ICD system may include an electrical housing electrode (sometimes referred to as a can electrode) that is coupled to one or more electrical lead wires placed within the heart. If an arrhythmia is sensed, the ICD may send a pulse via the electrical lead wires, and in some cases the can electrode, to shock the heart and restore its normal rhythm. In some examples, rather than placing and attaching electrical leads directly within the heart of a patient, extravascular ICD (EV- ICD) or other extracardiac ICD systems have been devised to provide shocks to the heart without placing electrical lead wires within the heart. In some cases, ICDs may deliver antitachyarrhythmia pacing (ATP) in response to sensing a tachyarrhythmia, e.g., prior to delivery of one or more shocks.SUMMARY

[0004] Aspects of the disclosure are directed to medical device systems configured to identify tachyarrhythmias, e.g., ventricular fibrillation (VF) and / or ventricular tachycardia (VT), such as extravascular ICD (EV-ICD) systems. EV-ICD systems are configured to deliver anti -tachyarrhythmia therapy (e.g., in the form of defibrillation shock(s) or cardioversion shock(s)) to a heart of a patient. Leads of EV-ICD systems are generally implanted in the anterior mediastinum or tissue adjacent to the anterior mediastinum. TheAty Ref. No. A0012803 WOO 1 mediastinal tissue, and thus any lead therein, moves relative to the heart during inspiration and expiration, e.g., since the heart is coupled to the diaphragm. EV-ICD leads can move several centimeters relative to cardiac tissue and may be sensitive to noise associated with surrounding muscle tissue, particularly at certain points in the respiratory cycle. In some examples, the noise associated with relative lead-heart motion and the surrounding muscle tissue may lead to false tachyarrhythmia detections. In some examples, the EV-ICD system may administer an unnecessary anti -tachyarrhythmia therapy, e.g., shocks or ATP, in response to a false tachyarrhythmia detection.

[0005] The techniques of this disclosure are directed to determining whether potential sensed tachyarrhythmia events are true sensed events or noise-related, false sensed events by determining whether an identified pattern in the sensed even corresponds to noise associated with the respiratory cycle. In some examples, the EV-ICD system may monitor a patient cardiac electrogram (EGM) signal or other physiological signal to identify potential tachyarrhythmia events.

[0006] Noise associated with respiration may increase periodically at one or more points in the respiratory cycle, which can lead to a burst of “fast” potential sensed events, e.g., depolarizations. The EV-ICD of the patient may identify a pattern of “fast” and “slow” potential sensed events. The EV-ICD or another device of a medical device system associated with the patient may sense a bioimpedance signal or another physiological signal indicative of the respiratory cycle to detect the respiratory cycle. If the potential sensed events have a pattern of “fast” sensed events, e.g., a threshold number of sensed events within a threshold period of time, that correspond to the respiratory cycle, the EV- ICD determines to withhold therapy, e.g., withhold shocks.

[0007] As an example, the EV-ICD may determine a predefined, threshold number, e.g., 8, potential sensed events have occurred within the period of time, e.g., 3 seconds. The EV-ICD may monitor a bioimpedance signal of the patient to detect the patient’s respiratory cycle. If the pattern corresponds to the detected respiratory cycle, the EV-ICD withholds therapy. In some examples, the EV-ICD may sense the bioimpedance signal continuously, periodically, or responsive to detecting fast potential sensed events. In some examples, monitoring the respiratory cycle in response to detecting fast potential sensed events may conserve battery life relative to continuously monitoring the respiratory cycle.Atty Ref. No. A0012803 WOO 1

[0008] In some examples, by determining whether to withhold therapy based on a determination of whether patterns of potential sensed events correspond to noise associated with the respiratory cycle, the techniques of this disclosure may improve an accuracy of tachyarrhythmia event detection, which may improve patient outcomes. For example, more accurate tachyarrhythmia event detection may lead to more appropriate clinical interventions. In examples in which the system is configured to delivery therapy, the techniques of this disclosure may, by determining to withhold therapy in response to determining the potential tachyarrhythmia episode is a false tachyarrhythmia episode, decrease unnecessary therapy administration, which may improve patient outcomes.

[0009] In some examples, in response to determining the sensed event is a false sensed event, the EV-ICD may determine to adjust a configuration of the EV-ICD. As an example, the EV-ICD may adjust a filter and / or adjust a sensing mode of the EV-ICD, e.g., the EV-ICD may determine to sense a cardiac EGM signal of the patient using different electrodes.

[0010] In some examples, in addition to or alternatively to determining whether a pattern of potential sensed events correspond to noise associated with the respiratory cycle to determine whether the potential ventricular tachyarrhythmia episode is true or false, the techniques of this disclosure may include determining whether the potential ventricular tachyarrhythmia episode is true or false based on the physiological signal indicative of respiration of the patient. In examples in which the physiological signal is a bioimpedance signal, e.g., a subcutaneous bioimpedance signal, the techniques may include determining, based on the bioimpedance signal, micro-changes in venous return, e.g., micro fluid shifts. These micro-changes in venous return may be related to the processes of inhalation and exhalation, which may be related to a micro-suction process for venous return to the heart.

[0011] In examples in which the patient is experiencing a true tachyarrhythmia episode, the micro-suction process may change relative to when the patient is experiencing normal sinus rhythm. For example, the process may be indicative of a decrease in pulsatility, which may be caused by the heart pumping less effectively during the tachyarrhythmia episode relative to during normal sinus rhythm. If the patient becomes fully hemodynamically compromised due to the tachyarrhythmia episode, the system may determine a loss of the time-varying bioimpedance signal.Atly Ref. No. A0012803 WOO 1

[0012] In some examples, a signature of the bioimpedance signal associated with changes in venous return may be different in VF, e.g., a rhythm not amenable to ATP and a hemodynamically compromised event, and in VT, e.g., an ATP amenable rhythm. In some examples, by differentiating between VT and VF, the techniques of this disclosure may improve one or more patient outcomes.

[0013] In one example, an implantable medical device comprises: sensing circuitry configured to: sense, via one or more electrodes of a plurality of electrodes, a cardiac EGM of a patient; and sense a physiological signal indicative of respiration of the patient; and processing circuitry configured to: identify a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on the physiological signal indicative of respiration of the patient, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0014] In another example, a method comprises: identifying, by processing circuitry of an implantable medical device comprising sensing circuity configured to sense, via one or more electrodes of a plurality of electrodes, a cardiac EGM of a patient, a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determining, by the processing circuitry, a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirming, by the processing circuitry and based on a physiological signal indicative of respiration of the patient sensed by the sensing circuitry, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determining, by the processing circuitry, the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0015] In another example, a non-transitory computer-readable medium comprises instructions that when executed cause processing circuitry to: identify a potentialAtty Ref. No. A0012803 WOO 1 ventricular tachyarrhythmia episode based on a cardiac EGM sensed by sensing circuitry of an implantable medical device via one or more electrodes of a plurality of electrodes; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on a physiological signal indicative of respiration of the patient sensed by the sensing circuitry of the implantable medical device that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0016] 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 apparatus and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.BRIEF DESCRIPTION OF DRAWINGS

[0017] FIGS. 1A, IB, and 1C are front- view, side-view, and top-view conceptual drawings, respectively, illustrating an example medical device system in conjunction with a patient, in accordance with one or more techniques of this disclosure.

[0018] FIG. 2 is a functional block diagram of an example configuration of electronic components of an example implantable medical device (IMD), in accordance with one or more techniques of this disclosure.

[0019] FIG. 3 is a flow diagram illustrating an example operation for determining whether a potential ventricular tachyarrhythmia episode is a false episode, in accordance with one or more techniques of this disclosure.

[0020] FIG. 4 is a flow diagram illustrating an example operation for determining whether a potential ventricular tachyarrhythmia episode is a false episode based on a comparison of intervals of a respiration of the patient to a pattern of the potential ventricular tachyarrhythmia episode, in accordance with one or more techniques of this disclosure.Atty Ref. No. A0012803 WOO 1

[0021] FIG. 5 is a graph illustrating an example cardiac electrogram (EGM) and respiration intervals of the patient, in accordance with one or more techniques of this disclosure.

[0022] Throughout the disclosure, like reference characters refer to like elements throughout the figures and description.DETAILED DESCRIPTION

[0023] A variety of types of implantable and external devices are configured to monitor health based on sensed cardiac electrograms (EGMs) and, in some cases, other physiological signals, such as an accelerometer signal, a pressure sensor signal, e.g., a blood pressure signal, an impedance signal, and / or a temperature signal. External devices that may be used to non-invasively sense and monitor cardiac EGMs and other physiological signals include wearable devices with electrodes configured to contact the skin of a patient, such as patches, watches, rings, necklaces, hearing aids, a wearable cardiac monitor or automated external defibrillator (AED), clothing, car seats, or bed linens. Such external devices may facilitate relatively longer-term monitoring of patient health during normal daily activities.

[0024] Implantable medical devices (IMDs) also sense and monitor cardiac EGMs and other physiological signals and detect health events such as episodes of arrhythmia, cardiac arrest, myocardial infarction, stroke, and seizure. Example HMDs include pacemakers and implantable cardioverter-defibrillators, which may be coupled to intravascular or extravascular leads, as well as pacemakers with housings configured for implantation within the heart, which may be leadless, such as the Micra™ AV Leadless Pacemaker and the Micra™ VR Leadless Pacemaker, available from Medtronic, Inc.

[0025] Some IMDs do not provide therapy, such as implantable patient monitors. One example of such an HMD is the Reveal LINQ™ or LINQ II™ insertable cardiac monitors (ICMs), available from Medtronic, Inc., which may be inserted subcutaneously. Such HMDs may facilitate relatively longer-term continuous monitoring of patients during normal daily activities, and may periodically or on demand transmit collected data, e.g.,Atty Ref. No. A0012803 WOO 1 episode data for detected arrhythmia episodes, to a remote patient monitoring system, such as the Medtronic CareLink™ Network via a home monitoring system or a smart phone application.

[0026] In some examples, a medical device system including an IMD, e.g., an extravascular implantable cardioverter defibrillator (EV-ICD), may provide antitachyarrhythmia therapy to a patient. The system may sense a physiological signal, e.g., a cardiac electrogram (EGM) to monitor for tachyarrhythmia events and another physiological signal, e.g., a bioimpedance signal, to determine whether a pattern of a potential tachyarrhythmia episode corresponds to noise associated with a respiratory cycle of the patient. The system may determine, based on a determination that the pattern corresponds to noise, that the potential tachyarrhythmia episode is a false episode.

[0027] The techniques of this disclosure may provide one or more technical and clinical advantages. For example, the techniques of this disclosure may improve an accuracy of tachyarrhythmia episode detections, which may improve patient outcomes. Additionally, in some examples, the techniques of this disclosure may be implemented by an IMD that can provide anti -tachyarrhythmia therapy, e.g., defibrillation shock or cardioversion, to the patient. The IMD may withhold therapy in response to determining the potential tachyarrhythmia episode is a false episode. By withholding antitachyarrhythmia based on the determination, the techniques of this disclosure may advantageously prevent unnecessary therapy administration, which may improve patient outcomes.

[0028] FIG. 1 A is a front view of a patient 12 implanted with the EV-ICD system 8 implanted intra-thoracically. Referring now to the drawings in which like reference designators refer to like elements, FIGS. 1 A-1C are conceptual diagrams illustrating various views of example extravascular EV-ICD system 8. EV-ICD system 8 includes an EV-ICD 9 connected to an implantable medical lead 10. FIG. 1 A is a front view of a patient implanted with EV-ICD system 8. FIG. IB is a side view of the patient implanted with EV-ICD system 8. FIG. 1C is a transverse view of the patient implanted with EV- ICD system 8.

[0029] EV-ICD 9 may include a housing that forms a hermetic seal that protects components of the EV-ICD 9. The housing of EV-ICD 9 may be formed of a conductive material, such as titanium or titanium alloy, which may function as a housing electrodeAtty Ref. No. A0012803 WOO 1(sometimes referred to as a can electrode). In some embodiments, EV-ICD 9 may be formed to have or may include a plurality of electrodes on the housing. EV-ICD 9 may also include a connector assembly (also referred to as a connector block or header) that includes electrical feedthroughs through which electrical connections are made between conductors of lead 10 and electronic components included within the housing of EV-ICD 9. As will be described in further detail herein, the housing may house one or more processors, memories, transmitters, receivers, sensors, sensing circuitry, therapy circuitry, power sources and other appropriate components. The housing is configured to be implanted in a patient, such as patient 12.

[0030] EV-ICD 9 is implanted extra-thoracically on the left side of the patient, e.g., under the skin and outside the ribcage (subcutaneously or submuscularly). EV-ICD 9 may, in some instances, be implanted between the left posterior axillary line and the left anterior axillary line of the patient. EV-ICD 9 may, in other instances, be implanted at other extra-thoracic locations on the patient.

[0031] Lead 10 may include an elongated lead body 13 having a distal portion 16 sized to be implanted in an extravascular location proximate the heart, e.g., intra- thoracically, as illustrated in FIGS. 1 A-1C, or extra-thoracically. For example, lead 10 may extend extra-thoracically under the skin and outside the ribcage (e.g., subcutaneously or submuscularly) from EV-ICD 9 toward the center of the torso of the patient, for example, toward the xiphoid process 23 of the patient. At a position proximate xiphoid process 23, the lead body 13 may bend or otherwise turn and extend superiorly. The bend may be pre-formed and / or lead body 13 may be flexible to facilitate bending. In the example illustrated in FIGS. 1 A-1C, the lead body 13 extends superiorly intra-thoracically underneath the sternum, in a direction substantially parallel to the sternum.

[0032] Distal portion 16 of lead 10 may reside in a substemal location such that distal portion 16 of lead 10 extends superior along the posterior side of the sternum substantially within the anterior mediastinum 36. Anterior mediastinum 36 may be viewed as being bounded laterally by pleurae 39, posteriorly by pericardium 38, and anteriorly by the sternum 22. In some instances, the anterior wall of anterior mediastinum 36 may also be formed by the transversus thoracis and one or more costal cartilages. Anterior mediastinum 36 includes a quantity of loose connective tissue (such as areolar tissue),Atly Ref. No. A0012803 WOO 1 adipose tissue, some lymph vessels, lymph glands, substernal musculature (e.g., transverse thoracic muscle), the thymus gland, branches of the internal thoracic artery, and the ITV.

[0033] Lead body 13 may extend superiorly extra-thoracically (instead of intra- thoracically), e.g., either subcutaneously or submuscularly above the ribcage / stemum. Lead 10 may be implanted at other locations, such as over the sternum, offset to the right of the sternum, angled lateral from the proximal or distal end of the sternum, or the like. In some examples, lead 10 may be implanted within an extracardiac vessel within the thorax, such as the ITV, the intercostal veins, the superior epigastric vein, or the azygos, hemiazygos, and accessory hemiazygos veins. In some examples, distal portion 16 of lead 10 may be oriented differently than is illustrated in FIGS. 1 A-1C, such as orthogonal or otherwise transverse to sternum 22 and / or inferior to heart 26. In such examples, distal portion 16 of lead 10 may be at least partially within anterior mediastinum 36. In some examples, distal portion 16 of lead 10 may be placed between the heart and lung as well as within the pleural cavity. In some examples, lead 10 may be implanted in the anterior mediastinum, intrapleurally, intrapericardially, epicardially, in the posterior mediastinum, and / or implanted through the intercostal space.

[0034] Lead body 13 may have a generally tubular or cylindrical shape and may define a diameter of approximately 3-9 French (Fr). However, lead bodies of less than 3 Fr and more than 9 Fr may also be utilized. In another configuration, lead body 13 may have a flat, ribbon, or paddle shape with solid, woven filament, or metal mesh structure, along at least a portion of the length of the lead body 13. In such an example, the width across lead body 13 may be between 1-3.5 mm. Other lead body designs may be used without departing from the scope of this application.

[0035] Lead body 13 may be formed from a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and other appropriate materials, and shaped to form one or more lumens (not shown), however, the techniques are not limited to such constructions. Distal portion 16 may be fabricated to be biased in a desired configuration, or alternatively, may be manipulated by the user into the desired configuration. For example, the distal portion 16 may be composed of a malleable material such that the user can manipulate the distal portion into a desired configuration where it remains until manipulated to a different configuration.Atly Ref. No. A0012803 WOO 1

[0036] Distal portion 16 includes electrodes configured to deliver electrical energy to the heart or sense electrical signals of the heart. Distal portion 16 may be anchored to a desired position within the patient, for example, substemally or subcutaneously by, for example, suturing distal portion 16 to the patient’s musculature, tissue, or bone at the xiphoid process entry site. In some examples, distal portion 16 may be anchored to the patient or through the use of rigid tines, prongs, barbs, clips, screws, and / or other projecting elements or flanges, disks, pliant tines, flaps, porous structures such as a meshlike elements and metallic or non-metallic scaffolds that facilitate tissue growth for engagement, bio-adhesive surfaces, and / or any other non-piercing elements. In addition to distal portion 16, lead body 13 may include a proximal end 14.

[0037] Lead body 13 may define a substantially linear portion 20 (FIG. 1 A) between proximal end 14 and distal portion 16 as it curves or bends near the xiphoid process 23 and extends superiorly. As shown in FIG. 1A, at least a part of distal portion 16 may define an undulating configuration distal to the substantially linear portion 20. In particular, distal portion 16 may define an undulating pattern, e.g., zig-zag, meandering, sinusoidal, serpentine, or other pattern, as it extends toward the distal end of lead 10. In other configurations, lead body 13 may not have a substantially linear portion 20 as it extends superiorly, but instead the undulating configuration may begin immediately after the bend.

[0038] Distal portion 16 includes one or more defibrillation electrodes configured to deliver an anti-tachyarrhythmia, e.g., cardioversion / defibrillation, shock to heart 26 of patient 12. In some examples, distal portion 16 includes a plurality of defibrillation electrodes spaced a distance apart from each other along the length of distal portion 16. In the example illustrated by FIGS. 1 A-1C, distal portion 16 includes two defibrillation electrodes 28a and 28b (collectively, “defibrillation electrodes 28”).

[0039] Defibrillation electrodes 28 may be disposed around or within the lead body 13 of the distal portion 16, or alternatively, may be embedded within the wall of the lead body 13. In one configuration, defibrillation electrodes 28 may be coil electrodes formed by a conductor. The conductor may be formed of one or more conductive polymers, ceramics, metal-polymer composites, semiconductors, metals or metal alloys, including but not limited to, one of a combination of the platinum, tantalum, titanium, niobium, zirconium, ruthenium, indium, gold, palladium, iron, zinc, silver, nickel, aluminum,Atly Ref. No. A0012803 WOO 1 molybdenum, stainless steel, MP35N, carbon, copper, polyaniline, polypyrrole, and other polymers. In another configuration, each of defibrillation electrodes 28 may be a flat ribbon electrode, a paddle electrode, a braided or woven electrode, a mesh electrode, a directional electrode, a patch electrode or another type of electrode configured to deliver a cardioversion / defibrillation shock to heart 26 of patient 12.

[0040] Defibrillation electrodes 28 may be electrically connected to one or more conductors, which may be disposed in the body wall of lead body 13 or in one or more insulated lumens (not shown) defined by lead body 13. In an example configuration, each of defibrillation electrodes 28 is connected to a common conductor such that a voltage may be applied simultaneously to all defibrillation electrodes 28 to deliver an antitachyarrhythmia shock to heart 26. In other configurations, defibrillation electrodes 28 may be attached to separate conductors such that each defibrillation electrode 28 may apply a voltage independent of the other defibrillation electrodes 28. In this case, EV-ICD 9 or lead 10 may include one or more switches or other mechanisms to electrically connect the defibrillation electrodes together to function as a common polarity electrode such that a voltage may be applied simultaneously to all defibrillation electrodes 28 in addition to being able to independently apply a voltage.

[0041] Distal portion 16 may also include one or more pacing and / or sensing electrodes configured to deliver pacing pulses to heart 26 and / or sense electrical activity of heart 26. Such electrodes may be referred to as pacing electrodes, sensing electrodes, or pace / sense electrodes. In the example illustrated by FIGS. 1 A-1C, distal portion 16 includes two pace / sense electrodes 32a and 32b (collectively, “pace / sense electrodes 32”).

[0042] In the illustrated example of FIGS. 1 A-1C, pace / sense electrode 32b is positioned between defibrillation electrodes 28, e.g., within a gap between the defibrillation electrodes, and pace / sense electrode 32a is positioned more proximal along distal portion 16 than proximal defibrillation electrode 28a. In some examples, more than one electrode 32 may exist within the gap between defibrillation electrodes 28. In some examples, an electrode 32 is additionally or alternatively located distal of the distalmost defibrillation electrode 28b.

[0043] Electrodes 32 may be configured to deliver low-voltage electrical pulses to the heart or may sense a cardiac electrical activity, e.g., depolarization and repolarization of the heart. As such, electrodes 32 may be referred to herein as pace / sense electrodes 32. InAtly Ref. No. A0012803 WOO 1 one configuration, electrodes 32 are ring electrodes. However, in other configurations electrodes 32 may be any of a number of different types of electrodes, including ring electrodes, short coil electrodes, paddle electrodes, hemispherical electrodes, or directional electrodes. Each of electrodes 32 may be the same or different types of electrodes as others of electrodes 32. Electrodes 32 may be electrically isolated from an adjacent defibrillation electrode 28 by including an electrically insulating layer of material between electrodes 32 and adjacent defibrillation electrodes 28. Each electrode 32 may have its own separate conductor such that a voltage may be applied to or sensed via each electrode independently from another electrode 32.

[0044] Electrodes 28 are referred to as defibrillation electrodes, and electrodes 32 are referred to as pace / sense electrodes, because they may have different physical structures enabling different functionality. Defibrillation electrodes 28 may be larger, e.g., have greater surface area, than pace / sense electrodes 32 and, consequently, may be configured to deliver anti-tachyarrhythmia shocks that have relatively higher voltages than pacing pulses. The relatively smaller size of pace / sense electrodes 32 may provide advantages over defibrillation electrodes for delivering pacing pulses and sensing intrinsic cardiac activity, e.g., lower pacing capture thresholds and / or better sensed signal quality. Nevertheless, a defibrillation electrode 28 may be used to deliver pacing pulses and / or sense electrical activity of the heart, such as in combination with a pace / sense electrode 32.

[0045] In the configuration shown in FIGS. 1 A-1C, each electrode 32 is substantially aligned along a major longitudinal axis (“x”). In one example, the major longitudinal axis is defined by a portion of elongate body 12, e.g., substantially linear portion 20. In another example, the major longitudinal axis is defined relative to the body of the patient, e.g., along the anterior median line (or midstemal line), one of the sternal lines (or lateral sternal lines), left parasternal line, or other line.

[0046] In one configuration, the midpoint of each electrode 32a and 32b is along the major longitudinal axis “x,” such that each electrode 32a and 32b is at least disposed at substantially the same horizontal position when the distal portion is implanted within the patient. In some examples, the longitudinal axis “x” may correspond to a caudal-cranial axis of the patient and a horizontal axis orthogonal to the longitudinal axis “x” may correspond to a medial-lateral axis of the patient. In other configurations, the electrodes 32Atly Ref. No. A0012803 WOO 1 may be disposed at any longitudinal or horizontal position along the distal portion 16 disposed between, proximal to, or distal to the defibrillation electrodes 28. In the example illustrated in FIG. 1 A, electrodes 32 are disposed along the undulating configuration of distal portion 16 at locations that will be closer to heart 26 of patient 12 than defibrillation electrodes 28 (e.g., at a peak of the undulating configuration that is toward the left side of the sternum). As illustrated in FIG. 1 A, for example, electrodes 32 are substantially aligned with one another along the left sternal line. In the example illustrated in FIG. 1 A, defibrillation electrodes 28 are disposed along peaks of the undulating configuration that extend toward a right side of the sternum away from the heart. This configuration places pace / sense electrodes 32 at locations closer to the heart than electrodes 28, to facilitate cardiac pacing and sensing at relatively lower amplitudes.

[0047] In some examples, pace / sense electrodes 32 and the defibrillation electrodes 28 may be disposed in a common plane when distal portion 16 is implanted extravascularly. In other configurations, the undulating configuration may not be substantially disposed in a common plane. For example, distal portion 16 may define a concavity or a curvature.

[0048] Proximal end 14 of lead body 13 may include one or more connectors 34 to electrically couple lead 10 to EV-ICD 9. EV-ICD 9 may also include a connector assembly that includes electrical feedthroughs through which electrical connections are made between the one or more connectors 34 of lead 10 and the electronic components included within the housing. The housing of EV-ICD 9 may house one or more processors, memories, transmitters, receivers, sensors, sensing circuitry, therapy circuitry, power sources (e.g., capacitors and batteries), and / or other components. The components of EV-ICD 9 may generate and deliver electrical therapy such as anti -tachyarrhythmia pacing (e.g., cardioversion or defibrillation shocks), post-shock pacing, and / or bradycardia pacing.

[0049] The undulating configuration of distal portion 16 and the inclusion of electrodes 32 between defibrillation electrodes 28 may provide a number of therapy vectors for the delivery of electrical therapy to the heart. For example, at least a portion of defibrillation electrodes 28 and one of electrodes 32 may be disposed over the right ventricle, or any chamber of the heart, such that pacing pulses and anti-tachyarrhythmia shocks may be delivered to the heart. The housing of EV-ICD 9 may be charged with or function as a polarity different than the polarity of the one or more defibrillation electrodesAtly Ref. No. A0012803 WOO 128 and / or electrodes 32 such that electrical energy may be delivered between the housing and the defibrillation electrode 28 and / or electrode 32 to the heart.

[0050] Each defibrillation electrode 28 may have the same polarity as every other defibrillation electrode 28 when a voltage is applied to it such that a shock may be delivered from all defibrillation electrodes together. In examples in which defibrillation electrodes 28 are electrically connected to a common conductor within lead body 13, this is the only configuration of defibrillation electrodes 28. However, in other examples, defibrillation electrodes 28 may be coupled to separate conductors within lead body 13 and may therefore each have different polarities such that electrical energy may flow between defibrillation electrodes 28, or between one of defibrillation electrodes 28 and one of pace / sense electrodes 32 or the housing electrode, to provide anti-tachyarrhythmia shock, pacing therapy, and / or to sense cardiac depolarizations. In this case, defibrillation electrodes 28 may still be electrically coupled together, e.g., via one or more switches within EV-ICD 9, to have the same polarity.

[0051] In some examples, EV-ICD system 8 may be sensitive to noise associated with the movement of muscle tissue during respiratory cycles of patient 12. In some examples, electrodes 28 and / or electrodes 32 may be sensitive to noise caused by breathing of patient 12. In some examples, lead 10 and / or EV-ICD 9 may be move during respiratory cycles of patient 12, which may lead to increased noise sensitivity. In some examples, the noise associated with the movement of muscle tissue during respiratory cycles of patient 12 can lead to inaccurate sensing of cardiac events, e.g., ventricular tachyarrhythmia episodes, which may lead to unnecessary therapy administration, e.g., unnecessary antitachyarrhythmia shocks. The techniques of this disclosure include identifying potential inaccurately sensed ventricular tachyarrhythmia episodes based on a determination that a pattern of a potentially inaccurately sensed ventricular tachyarrhythmia episode corresponds to respiration of a patient, e.g., patient 12. In some examples, the techniques further include withholding therapy in response to the identification of the inaccurately sensed ventricular tachyarrhythmia episode, which may prevent unnecessary therapy administration and improve patient outcomes.

[0052] One of more of electrodes 28 and / or electrodes 32 may be configured to sense a signal indicative of a respiration of patient 12, such as a bioimpedance signal. Additionally, or alternatively, EV-ICD system 8 may include one or more additionalAtly Ref. No. A0012803 WOO 1 sensors (not depicted) configured to sense the signal, such as an accelerometer signal or a pressure signal. In some examples, to determine that the pattern of the inaccurately sensed ventricular tachyarrhythmia episode corresponds to respiration of patient 12, EV-ICD system 8 compares a cardiac EGM and / or one or more feature or patterns of the EGM sensed by one or more of electrodes 28 and / or electrodes 32 to the signal indicative of the respiration of patient 12 and / or one or more features of the signal indicative of the respiration of patient 12.

[0053] FIG. 2 is a functional block diagram of an example configuration of electronic components and other components of EV-ICD 9, in accordance with one or more techniques of this disclosure. EV-ICD 9 includes a processing circuitry 202, sensing circuitry 204, therapy delivery circuitry 206, sensors 208, communication circuitry 210, and memory 212. In some examples, ICD 9 may include more or fewer components. The described circuitry and other components may be implemented together on a common hardware component or separately as discrete but interoperable hardware or software components. Depiction of different features is intended to highlight different functional aspects and does not necessarily imply that such circuitry and other components must be realized by separate hardware or software components. Rather, functionality associated with one or more circuitries and components may be performed by separate hardware or software components or integrated within common or separate hardware or software components.

[0054] Sensing circuitry 204 may be electrically coupled to some or all of electrodes 216, which may correspond to any of the defibrillation, pace / sense, and housing electrodes described herein, e.g., electrodes 28 and electrodes 32 of FIGS. 1A-1C. Sensing circuitry 204 is configured to obtain signals sensed via one or more combinations of electrodes 216 and process the obtained signals.

[0055] The components of sensing circuitry 204 may be analog components, digital components or a combination thereof. Sensing circuitry 204 may, for example, include one or more sense amplifiers, filters, rectifiers, threshold detectors, analog-to-digital converters (ADCs) or the like. Sensing circuitry 204 may convert the sensed signals to digital form and provide the digital signals to processing circuitry 202 for processing or analysis. For example, sensing circuitry 204 may amplify signals from the sensing electrodes and convert the amplified signals to multi-bit digital signals by an ADC.Atty Ref. No. A0012803 WOO 1Sensing circuitry 204 may also compare processed signals to a threshold to detect the existence of atrial or ventricular depolarizations (e.g., P- or R waves) and indicate the existence of the atrial depolarization (e.g., P-waves) or ventricular depolarizations (e.g., R- waves) to processing circuitry 202. As shown in FIG. 2, EV-ICD 9 may additionally include one or more sensors 208, such as one or more accelerometers or pressure sensors, which may be configured to provide signals indicative of other parameters of a patient, such as respiration, to processing circuitry 202.

[0056] Processing circuitry 202 may process the signals from sensing circuitry 204 to monitor respiration of patient 12 and electrical activity of heart 26 of patient 12.Processing circuitry 202 may store signals obtained by sensing circuitry 204 as well as any generated cardiac EGM waveforms, respiration signals waveforms, e.g., bioimpedance waveforms, marker channel data or other data derived based on the sensed signals in memory 212. Processing circuitry 202 may analyze the EGM waveforms and / or marker channel data to detect ventricular tachyarrhythmias (e.g., ventricular fibrillation or ventricular tachycardia). In response to detecting the ventricular tachyarrhythmia, processing circuitry 202 may control therapy delivery circuitry 206 to deliver the desired therapy to treat the ventricular tachyarrhythmia, e.g., an anti-tachyarrhythmia shock, e.g., a defibrillation shock or cardioversion shock. In some examples, before controlling therapy delivery circuitry 206 to deliver the therapy, processing circuitry may determine a pattern in the EGM corresponding to the ventricular tachyarrhythmia potentially corresponds to noise associated with respiration of the patient. In some examples, sensing circuitry 204 continuously senses a physiological signal indicative of respiration of patient 12, e.g., a bioimpedance signal of patient 12. In some examples, sensing circuitry senses the bioimpedance signal in response to determining the pattern in the EGM corresponds to noise associated with respiration of the patient. In some examples, processing circuitry 202 compares the pattern of the EGM to the bioimpedance signal to determine whether the pattern of the EGM corresponds to noise associated with respiration of patient 12. If the pattern of the EGM corresponds to noise, processing circuitry 202 may control therapy delivery circuitry 206 to withhold therapy.

[0057] In some examples, in addition to or alternatively to determining whether pattern of potential sensed events correspond to noise associated with the respiratory cycle to determine whether the potential ventricular tachyarrhythmia episode is true or false,Atly Ref. No. A0012803 WOO 1 processing circuitry 202 may sense the bioimpedance signal of patient 12 to determine whether changes in the bioimpedance signal are indicative of changes in venous return, e.g., micro fluid shifts, which may be related to the processes of inhalation and exhalation. The processes of inhalation and exhalation may be related to a micro-suction process for venous return.

[0058] In examples in which the patient is experiencing a true tachyarrhythmia episode, the micro-suction process may change relative to when the patient is experiencing normal sinus rhythm. For example, the process may be indicative of a decrease in pulsatility, which may be caused by the heart pumping less effectively during the tachyarrhythmia episode relative to during normal sinus rhythm. If the patient becomes fully hemodynamically compromised due to the tachyarrhythmia episode, the processing circuitry 202 may determine a loss of the time-varying bioimpedance signal.

[0059] In some examples, a signature associated with the bioimpedance signal indicative of the venous return of patient 12 may be different in VF and VT. In some examples, VF is a non-antitachyarrhythmia pacing (ATP) amenable rhythm and a hemodynamically compromised event, and VT is an ATP amenable rhythm. In some examples, processing circuitry 202 may differentiate between VT and VF of the patient based on this difference in signature between VT and VF, which may improve patient outcomes.

[0060] Therapy delivery circuitry 206 is configured to generate and deliver electrical therapy to heart 26. Therapy delivery circuitry 206 may include one or more pulse generators, capacitors, and / or other components capable of generating and / or storing energy to deliver as pacing therapy, antitachyarrhythmia therapy (e.g., defibrillation therapy and cardioversion therapy), cardiac resynchronization therapy, other therapy, or a combination of therapies. In some instances, therapy delivery circuitry 206 may include a first set of components configured to provide pacing therapy and a second set of components configured to provide defibrillation therapy. In some instances, therapy delivery circuitry 206 may utilize the same set of components to provide both pacing and defibrillation therapy. In still other instances, therapy delivery circuitry 206 may share some of the defibrillation and pacing therapy components while using other components solely for defibrillation or pacing. Processing circuitry 202 may control therapy delivery circuitry 206 to deliver the generated therapy to heart 26 via one or more combinations ofAty Ref. No. A0012803 WOO 1 electrodes 216. Although not shown in FIG. 2, EV-ICD 9 may include switching circuitry configurable by processing circuitry 202 to control which of electrodes 216 is connected to therapy delivery circuitry 206 and sensing circuitry 204.

[0061] Communication circuitry 210 may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as a clinician programmer, a patient monitoring device, or the like. For example, communication circuitry 210 may include appropriate modulation, demodulation, frequency conversion, filtering, and amplifier components for transmission and reception of data with the aid of an antenna.

[0062] The various components of EV-ICD 9 may include any one or more processors, controllers, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete or integrated circuitry, including analog circuitry, digital circuitry, or logic circuitry. Processing circuitry 202 may include fixed function circuitry and / or programmable processing circuitry. The functions attributed to processing circuitry 202 herein may be embodied as software, firmware, hardware or any combination thereof.

[0063] Memory 212 may include computer-readable instructions that, when executed by processing circuitry 202 or other components of EV-ICD 9, cause one or more components of EV-ICD 9 to perform various functions attributed to those components in this disclosure. Memory 212 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), static non-volatile RAM (SRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other non-transitory computer- readable storage media.

[0064] FIG. 3 is a flow diagram illustrating an example operation for determining whether a potential ventricular tachyarrhythmia episode is a false episode, in accordance with one or more techniques of this disclosure. Sensing circuitry 204 of EV-ICD 9 senses a cardiac EGM via one or more electrodes 216 of a plurality of electrodes 216, e.g., via electrodes 32a and 32b of electrodes 28 and electrodes 32 (302). Sensing circuitry 204 may sense the cardiac EGM continuously, which may also include sensing on a regular periodic schedule. Processing circuitry 202 identifies a potential ventricular tachyarrhythmia episode based on the cardiac EGM (304). In some examples, processingAtty Ref. No. A0012803 WOO 1 circuitry 202 identifies the potential ventricular tachyarrhythmia episode based on one or more features of the cardiac EGM and / or the cardiac EGM signal. Processing circuitry 202 determines whether a pattern of the cardiac EGM may be indicative of noise associated with respiration (306). In some examples, processing circuitry 202 determines the pattern may be indicative of noise associated with respiration when the pattern includes a threshold number of sensing events, e.g., eight or more, within a threshold period of time, such as 3 seconds, e.g., a burst of “fast sensing events.” In some examples, the pattern may include one or more slow sensing events followed by a burst of fast sensing events and another one or more slow sensing events within the threshold period of time.

[0065] If the pattern of the cardiac EGM including the potential ventricular tachyarrhythmia episode is not indicative of noise associated with respiration, e.g., if the pattern does not include the threshold number of sensing events within the threshold period of time (“NO” of 306), processing circuitry 202 determines the ventricular tachyarrhythmia event is a true ventricular tachyarrhythmia event (308). In some examples, processing circuitry 202 may control therapy delivery circuitry 206 to deliver therapy, e.g., an anti-tachyarrhythmia shock, to heart 26 of patient 12 via one or more of electrodes 216, e.g., electrodes 28 of lead 10 of FIG. 1. If the pattern of the cardiac EGM including the potential ventricular tachyarrhythmia episode is indicative of noise associated with respiration, e.g., if the pattern includes the threshold number of sensing events within the threshold period of time (“YES” of 306), processing circuitry 202 controls sensing circuitry 204 to sense a physiological signal of the patient (310). In some examples, the physiological signal is a bioimpedance signal of patient 12, and sensing circuitry 204 senses the bioimpedance signal, via one or more of electrodes 216. In some examples, the one or more of electrodes 216 that sense the bioimpedance signal are the same one or more electrodes 216 that sense the cardiac EGM, e.g., electrodes 32a and 32b. In some examples, processing circuitry 202 additionally or alternatively controls sensing circuitry 204 to sense another physiological signal indicative of respiration of patient 12, such as an accelerometer signal via sensor(s) 208. In some examples, sensing circuitry 204 continuously senses the bioimpedance signal and / or other physiological signal indicative of respiration.

[0066] In some examples, in addition to determining whether the pattern of the cardiac EGM may be indicative of noise associated with respiration, processing circuitry 202 mayAtty Ref. No. A0012803 WOO 1 determine whether one or more additional features are indicative of noise or a true ventricular tachyarrhythmia event. The one or more additional features may include one or more of a noise morphology feature of the cardiac EGM or a P-wave oversensing feature. In some examples, processing circuitry 202 determines the one or more additional features in response to determining the pattern includes the threshold number of sensing events within the threshold period of time. In some examples, processing circuitry 202 determines the one or more additional features continuously or periodically independent of the pattern of the cardiac EGM including the threshold number of sensing events within threshold period of time. In some examples, processing circuitry 202 determines to control sensing circuitry 204 to sense the physiological signal of the patient (310) in response to both the determination that the pattern of the cardiac EGM includes the threshold number of sensing events and the one or more additional features are indicative of noise.

[0067] Processing circuitry 202 determines respiration of patient 12 based on the bioimpedance signal and / or other physiological signal (312). In some examples, determining respiration of patient 12 includes determining inspiration phases and expiration phases of patient 12. In some examples, determining respiration of patient 12 includes determining respiration rate of patient 12. In some examples, determining the respiration of patient 12 includes determining respiration intervals of patient 12. Processing circuitry 202 determines whether the pattern of the cardiac EGM including the potential ventricular tachyarrhythmia episode corresponds to noise associated with respiration of patient 12 by comparing the pattern to the bioimpedance signal and / or other physiological signal indicative of respiration (314). As an example, processing circuitry 202 may compare the pattern to the bioimpedance signal by determining whether a variation of heart rate in the cardiac EGM corresponds a respiration metric based on the bioimpedance signal. As another example, processing circuitry 202 may determine whether the variation of heart rate in the cardiac EGM corresponds to respiration cycles in the bioimpedance signal. If the pattern does not correspond to noise associated with respiration of the patient (“NO” of 314), processing circuitry 202 may determine the potential ventricular tachyarrhythmia episode is a true ventricular tachyarrhythmia episode (308).

[0068] If the pattern corresponds to noise associated with respiration of the patient (“YES” of 314), processing circuitry 202 determines the potential ventricularAtty Ref. No. A0012803 WOO 1 tachyarrhythmia episode is a false ventricular tachyarrhythmia episode (316). In some examples, to determine the pattern corresponds to noise associated with respiration of the patient, processing circuitry 202 determines whether the burst of fast sensing events occurred during a point in a respiratory cycle of patient 12 in which EV-ICD system 8 was expected to be relatively sensitive to noise compared to other points in the respiratory cycle. For example, EV-ICD system 8 may be relatively sensitive to noise during at various points of an inspiration phase of the respiratory cycle and / or may be relatively sensitive to noise during transitions between inspiration phases and expiration phases. In some examples, to determine the pattern corresponds to noise associated with respiration of the patient, processing circuitry 202 determines whether the burst of fast sensing events occurred while the respiratory cycle of patient 12 was relatively unstable or when patient 12 was breathing relatively quickly, such as during exercise. In some examples, if the patient is breathing relatively quickly, EV-ICD system 8 may be more sensitive to noise due to the relatively shorter period of time between transitions from inspiration to expiration and from expiration to inspiration. In some examples, processing circuitry 202 determines to withhold therapy delivery in response to confirming that the potential ventricular tachyarrhythmia episode is a false episode (318).

[0069] In some examples, in addition to or alternatively to withholding therapy delivery, processing circuitry 202 may determine to adjust a configuration of EV-ICD system 8, e.g., adjust a configuration of EV-ICD 9, in response to determining the potential ventricular tachyarrhythmia episode is a false ventricular tachyarrhythmia episode. As an example, processing circuitry 202 may determine to adjust filtering of the cardiac EGM signal. Additionally, or alternatively, processing circuitry 202 may switch to a different sensing mode, e.g., processing circuitry 202 may control sensing circuitry 204 to sense the cardiac EGM using a different electrode combination of electrodes 216.

[0070] In some examples, in addition to or alternatively to determining whether pattern of potential sensed events correspond to noise associated with the respiratory cycle to determine whether the potential ventricular tachyarrhythmia episode is true or false, processing circuitry 202 may sense the bioimpedance signal of patient 12 to determine whether changes in the bioimpedance signal are indicative of changes in venous return, e.g., micro fluid shifts, which may be related to the processes of inhalation and exhalation. The processes of inhalation and exhalation may be related to a micro-suction process forAtly Ref. No. A0012803 WOO 1 venous return. Processing circuitry 202 may determine whether a change in venous return is indicative of a true tachyarrhythmia episode or a false tachyarrhythmia episode.

[0071] In examples in which the patient is experiencing a true tachyarrhythmia episode, the micro-suction process may change relative to when the patient is experiencing normal sinus rhythm. For example, the process may be indicative of a decrease in pulsatility, which may be caused by the heart pumping less effectively during the tachyarrhythmia episode relative to during normal sinus rhythm. If processing circuitry 202 determines a loss of the time-varying bioimpedance signal, processing circuitry 202 may determine patient 12 has become fully hemodynamically compromised due to the tachyarrhythmia episode.

[0072] In some examples, a signature associated with the bioimpedance signal indicative of the venous return of patient 12 may be different in VF and VT. In some examples, VF is a non-antitachyarrhythmia pacing (ATP) amenable rhythm and a hemodynamically compromised event, and VT is an ATP amenable rhythm. In some examples, processing circuitry 202 may differentiate between VT and VF of the patient based on this difference in signature between VT and VF, which may improve patient outcomes. As an example, by differentiation between VT and VF, the techniques of this disclosure may facilitate appropriate treatment of the VT or VF episode.

[0073] FIG. 4 is a flow diagram illustrating an example operation for determining whether a potential ventricular tachyarrhythmia episode is a false episode based on a comparison of intervals of a respiration of the patient to a pattern of the potential ventricular tachyarrhythmia episode, in accordance with one or more techniques of this disclosure. In some examples, FIG. 4 may be a specific example of portions of the example operation of FIG. 3.

[0074] In response to determining a potential ventricular tachyarrhythmia episode has a pattern indicative of noise associated with respiration of a patient, e.g., patient 12, processing circuitry 202 may determine to confirm whether the potential ventricular tachyarrhythmia episode is a true episode or a false episode. To confirm whether the potential ventricular tachyarrhythmia episode is a true episode or a false episode, processing circuitry may determine intervals of respiration of patient 12, e.g., respiration cycle lengths of patient 12 (402). Processing circuitry 202 compares the intervals of the respiration to the pattern of the cardiac EGM, e.g., pattern of cardiac cycle lengths or heartAtly Ref. No. A0012803 WOO 1 rates, including the potential ventricular tachyarrhythmia episode (404). In some examples, comparing the intervals of the respiration to the pattern of the cardiac EGM including the potential ventricular tachyarrhythmia episode includes determining whether the timing of the pattern of the cardiac EGM, e.g., timing of changes in cardiac cycle lengths or heart rates, aligns with times that the respiration rate of the patient was relatively short. In some examples, EV-ICD system 8 may be more sensitive to noise during transitions between inspiration and expiration than during other times in the respiratory cycle. When patient 12 is breathing relatively quickly, the time between transitions from inspiration and expiration and from expiration to inspiration are shorter than when the patient is breathing at a more normal rate. The time between transition periods is then relatively shorter, making EV-ICD system 8 more sensitive to noise at more frequent intervals. Processing circuitry 202 determines whether timing of the pattern of the cardiac EGM including the potential ventricular tachyarrhythmia episode corresponds to timing of relatively short respiration intervals (406). If the pattern does not correspond to the respiration intervals, e.g., if the pattern occurred when respiration intervals were relatively long (“NO” of 406), processing circuitry 202 may determine the potential ventricular tachyarrhythmia episode is a true ventricular tachyarrhythmia episode (408). In some examples, processing circuitry may control therapy delivery circuitry 206 to delivery therapy, e.g., an anti -tachyarrhythmia shock, to heart 26 of patient 12.

[0075] If the pattern corresponds to the respiration intervals, e.g., if the pattern occurred when respiration intervals were relatively short (“YES” of 406), processing circuitry 202 determines the potential ventricular tachyarrhythmia episode is a false ventricular tachyarrhythmia episode (410). In some examples, processing circuitry 202 may determine to withhold therapy delivery, e.g., withhold the anti-tachyarrhythmia shock (412).

[0076] In some examples, in addition to or alternatively to withholding therapy delivery, processing circuitry 202 may determine to adjust a configuration of EV-ICD system 8, e.g., adjust a configuration of EV-ICD 9, in response to determining the potential ventricular tachyarrhythmia episode is a false ventricular tachyarrhythmia episode. As an example, processing circuitry 202 may determine to adjust filtering of the cardiac EGM signal. Additionally, or alternatively, processing circuitry 202 may switch toAtly Ref. No. A0012803 WOO 1 a different sensing mode, e.g., processing circuitry 202 may control sensing circuitry 204 to sense the cardiac EGM using a different electrode combination of electrodes 216.

[0077] FIG. 5 is a graph illustrating an example cardiac EGM and respiration intervals of the patient, in accordance with one or more techniques of this disclosure. Cardiac EGM 502 is an example cardiac EGM of a patient, e.g., patient 12, over a period of time. Respiration intervals 504 is an example depiction of respiration intervals of patient 12 over the period of time. In some examples, processing circuitry 202 determines the respiration intervals based on the physiological signal indicative of respiration of patient 12. In some examples, the physiological signal is a bioimpedance signal. In some examples, a cardiac EGM signal may be susceptible to noise related to motion artifacts and / or muscle tissue associated with patient breathing. The noise in the signal may manifest in the cardiac EGM as a burst of fast sensing events, such as burst 508, which may be proceeded by relatively slow or normal sensing events, such as normal waveforms 506. Burst 508 may be misinterpreted as a ventricular tachyarrhythmia episode. EV-ICD system 8 may be configured to determine whether a potential ventricular tachyarrhythmia episode is a true episode or a false episode before controlling therapy delivery circuitry 206 to delivery anti-tachyarrhythmia therapy.

[0078] In some examples, to determine whether the potential tachyarrhythmia episode is a true episode or a false episode, processing circuitry 202 of EV-ICD system 8 may compare cardiac EGM 502 and respiration intervals 504. For example, processing circuitry 202 may compare burst 508 to a corresponding portion of respiration intervals 504, i.e., burst respiration intervals 512. Respiration intervals 512 are relatively short, e.g., compared to normal intervals 510, which in some examples may indicate that EV-ICD system 8 was relatively sensitive to noise during the time at which burst 508, i.e., the potential ventricular tachyarrhythmia episode, was identified.

[0079] Example 1. An implantable medical device comprising: sensing circuitry configured to: sense, via one or more electrodes of a plurality of electrodes, a cardiac electrogram (EGM) of a patient; and sense a physiological signal indicative of respiration of the patient; and processing circuitry configured to: identify a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potentialAtly Ref. No. A0012803 WOO 1 tachyarrhythmia episode potentially corresponds to noise, confirm, based on the physiological signal indicative of respiration of the patient, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0080] Example 2. The system of example 1, wherein one or more electrodes of the plurality of electrodes comprises a first one or more electrodes, and wherein the implantable medical device comprises therapy delivery circuitry configured to deliver therapy to the patient via a second one or more of the plurality of electrodes in response to identifying a tachyarrhythmia episode.

[0081] Example 3. The system of example 2, wherein the therapy comprises an anti-tachyarrhythmia shock.

[0082] Example 4. The system of any of examples 2-3, wherein the processing circuitry is further configured to: in response to the determination that the potential tachyarrhythmia episode is a false tachyarrhythmia episode, withhold the therapy.

[0083] Example 5. The system of any of example 1-4, wherein the processing circuitry is configured to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise.

[0084] Example 6. The system of any of examples 1-5, wherein the pattern comprises a burst of fast sensing events.

[0085] Example 7. The system of example 6, wherein the burst of fast sensing events comprises a threshold number of sensing events within a threshold period of time.

[0086] Example 8. The system of any of examples 1-7, wherein the processing circuitry is configured to control the sensing circuitry to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient.

[0087] Example 9. The system of any of examples 1-8, wherein to determine, based on the physiological signal indicative of respiration of the patient, the pattern corresponds to noise associated with respiration of the patient, the processing circuitry is configured to: based on the physiological signal indicative of respiration of the patient,Atly Ref. No. A0012803 WOO 1 determine intervals of respiration of the patient; compare the intervals of the respiration to the pattern of the potential tachyarrhythmia episode; and determine the pattern corresponds to the intervals of the respiration.

[0088] Example 10. The system of any of examples 1-9, wherein the physiological signal indicative of respiration of the patient comprises a bioimpedance signal.

[0089] Example 11. The system of any of examples 1-10, wherein the implantable medical device comprises an extravascular implantable cardioverter defibrillator (EV-ICD).

[0090] Example 12. A method comprising: identifying, by processing circuitry of an implantable medical device comprising sensing circuity configured to sense, via one or more electrodes of a plurality of electrodes, a cardiac electrogram (EGM) of a patient, a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determining, by the processing circuitry, a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirming, by the processing circuitry and based on a physiological signal indicative of respiration of the patient sensed by the sensing circuitry, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determining, by the processing circuitry, the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0091] Example 13. The method of example 12, wherein the one or more electrodes of the plurality of electrodes comprises a first one or more electrodes, and wherein the implantable medical device comprises therapy delivery circuitry configured to deliver therapy to the patient via a second one or more of the plurality of electrodes in response to identifying a tachyarrhythmia episode.

[0092] Example 14. The method of example 13, wherein the therapy comprises an anti-tachyarrhythmia shock.

[0093] Example 15. The method of any of examples 13-14, further comprising: withholding, by the processing circuitry and in response to the determination that the potential tachyarrhythmia episode is a false tachyarrhythmia episode, the therapy.Aty Ref. No. A0012803 WOO 1

[0094] Example 16. The method of any of example 12-15, wherein the processing circuitry is configured to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise.

[0095] Example 17. The method of any of examples 12-16, wherein the pattern comprises a burst of fast sensing events.

[0096] Example 18. The method of example 17, wherein the burst of fast sensing events comprises a threshold number of sensing events within a threshold period of time.

[0097] Example 19. The method of any of examples 12-18, wherein sensing the physiological signal indicative of respiration of the patient comprises controlling the sensing circuitry to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient.

[0098] Example 20. The method of any of examples 12-19, wherein determining, based on the physiological signal indicative of respiration of the patient, the pattern corresponds to noise associated with respiration of the patient comprises: determining, by the processing circuitry and based on the physiological signal indicative of respiration of the patient, intervals of respiration of the patient; comparing, by the processing circuitry, the intervals of the respiration to the pattern of the potential tachyarrhythmia episode; and determining, by the processing circuitry, the pattern corresponds to the intervals of the respiration.

[0099] Example 21. The method of any of examples 12-20, wherein the physiological signal indicative of respiration of the patient comprises a bioimpedance signal.

[0100] Example 22. The method of any of examples 13-21, wherein the implantable medical device comprises an extravascular implantable cardioverter defibrillator (EV-ICD).

[0100] Example 23. A non-transitory computer-readable medium comprising instructions that when executed cause processing circuitry to: identify a potential ventricular tachyarrhythmia episode based on a cardiac EGM sensed by sensing circuitry of an implantable medical device via one or more electrodes of a plurality of electrodes; determine a pattern of the potential ventricular tachyarrhythmia episode potentiallyAtly Ref. No. A0012803 WOO 1 corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on a physiological signal indicative of respiration of the patient sensed by the sensing circuitry of the implantable medical device, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

[0101] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

Atly Ref. No. A0012803 WOO 1WHAT IS CLAIMED IS:

1. An implantable medical device comprising: sensing circuitry configured to: sense, via one or more electrodes of a plurality of electrodes, a cardiac electrogram (EGM) of a patient; and sense a physiological signal indicative of respiration of the patient; and processing circuitry configured to: identify a potential ventricular tachyarrhythmia episode based on the cardiac EGM; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on the physiological signal indicative of respiration of the patient, that the pattern corresponds to noise associated with respiration of the patient; and based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

2. The system of claim 1, wherein one or more electrodes of the plurality of electrodes comprises a first one or more electrodes, and wherein the implantable medical device comprises therapy delivery circuitry configured to deliver therapy to the patient via a second one or more of the plurality of electrodes in response to identifying a tachyarrhythmia episode.

3. The system of claim 2, wherein the therapy comprises an anti -tachyarrhythmia shock.

4. The system of any of claims 2-3, wherein the processing circuitry is further configured to: in response to the determination that the potential tachyarrhythmia episode is a false tachyarrhythmia episode, withhold the therapy.Atly Ref. No. A0012803 WOO 15. The system of any of claim 1-4, wherein the processing circuitry is configured to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise.

6. The system of any of claims 1-5, wherein the pattern comprises a burst of fast sensing events.

7. The system of claim 6, wherein the burst of fast sensing events comprises a threshold number of sensing events within a threshold period of time.

8. The system of any of claims 1-7, wherein the processing circuitry is configured to control the sensing circuitry to sense the physiological signal indicative of respiration of the patient in response to the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient.

9. The system of any of claims 1-8, wherein to determine, based on the physiological signal indicative of respiration of the patient, the pattern corresponds to noise associated with respiration of the patient, the processing circuitry is configured to: based on the physiological signal indicative of respiration of the patient, determine intervals of respiration of the patient; compare the intervals of the respiration to the pattern of the potential tachyarrhythmia episode; and determine the pattern corresponds to the intervals of the respiration.

10. The system of any of claims 1-9, wherein the processing circuitry is configured to adjust a configuration of the implantable medical device in response to the determination that the potential ventricular tachyarrhythmia episode is a false ventricular tachyarrhythmia episode.Atly Ref. No. A0012803 WOO 111. The system of any of claims 1-10, wherein the physiological signal indicative of respiration of the patient comprises a bioimpedance signal.

12. The system of claim 11, wherein the tachyarrhythmia episode comprises a ventricular tachycardia (VT) episode or a ventricular fibrillation (VF) episode, and wherein the processing circuitry is configured to determine whether the tachyarrhythmia episode is a VT episode or a VF episode based on a signature of the bioimpedance signal.

13. The system of claim 12, wherein to determine whether the tachyarrhythmia episode is a VT episode or a VF episode based on a signature of the bioimpedance signal, the processing circuitry is configured to: determine a change in venous return based on the bioimpedance signal; and based on the change in venous return, determine whether the tachyarrhythmia episode is a VT episode or a VF episode.

14. The system of any of claims 1-13, wherein the implantable medical device comprises an extravascular implantable cardioverter defibrillator (EV-ICD).

15. A non-transitory computer-readable medium comprising instructions that when executed cause processing circuitry to: identify a potential ventricular tachyarrhythmia episode based on a cardiac EGM sensed by sensing circuitry of an implantable medical device via one or more electrodes of a plurality of electrodes; determine a pattern of the potential ventricular tachyarrhythmia episode potentially corresponds to noise associated with respiration of the patient; based on the determination that the pattern of the potential tachyarrhythmia episode potentially corresponds to noise, confirm, based on a physiological signal indicative of respiration of the patient sensed by the sensing circuitry of the implantable medical device, that the pattern corresponds to noise associated with respiration of the patient; andAty Ref. No. A0012803 WOO 1 based on the confirmation that the pattern corresponds to noise associated with respiration of the patient, determine the potential ventricular tachyarrhythmia episode is a false tachyarrhythmia episode.

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