Selectively activating a filter for sensing cardiac signals

Abstract

An example medical device includes a memory; and processing circuitry coupled to the memory, the processing circuitry is configured to: receive, from one or more electrodes coupled to the medical device, a cardiac signal of a patient; determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

Description

Atty Ref. No: A0012209W001SELECTIVELY ACTIVATING A FILTER FOR SENSING CARDIAC SIGNALS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 691,871, filed September 6, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present application relates to an implantable medical device and, more particularly, implantable medical devices configured to sense tachyarrhythmias.BACKGROUND

[0003] Sudden cardiac death (SCD) affects more than 300,000 patients annually and accounts for nearly 6% of the annual mortality in the U.S., the vast majority due to fatal arrhythmias. Implantable cardioverter defibrillators (ICDs) are used to prevent SCD by applying low voltage electrical stimulation (e.g., anti-tachycardia pacing [ATP]) and / or a high voltage (e.g., defibrillation) electrical shock to the heart when a life-threatening arrhythmia is detected. Endocardial delivery of ATP may minimize patient pain and discomfort by reducing the number of defibrillation shocks delivered.

[0004] Implantation of transvenous leads for intracardiac pacing and defibrillation is not always possible due to anatomic anomalies, occluded vessels, or other issues. For these patients, an extravascular ICD (EV-ICD) system may provide an opportunity to receive life-saving implantable pacing / defibrillation systems. An EV-ICD system may include an extravascular lead that may be implanted in the substernal space and a device implanted on the thorax.SUMMARY

[0005] Noise, such as electromagnetic interference (EMI), may cause false ventricular depolarization detections, which may lead to false tachyarrhythmia detections by implantable medical devices (IMDs), and result in subsequent unnecessary delivery of shocks or other therapeutic electrical signals to patients with ICDs. False ventricular depolarization detection may also lead to undesired inhibition of pacing therapy by IMDs.Atly Ref. No: A0012209W001In addition, some IMDs may not filter noise signals because the filters that filter or discriminate noise from cardiac signals have substantial current drain that may decrease the longevity of the IMD, reduce sensitivity of sensing and detection by the IMD, and / or have conflicting interactions with other features or devices.

[0006] The techniques of this disclosure are directed to selectively activating a filter, such as a notch filter, to filter noise, such as EMI, from cardiac signals without compromising detection sensitivity while at the same time minimizing the decrease in longevity of the ICD or other IMD and conflicting feature interactions with other devices. In accordance with the techniques of the disclosure, an IMD may be configured to selectively enable the noise filter(s), such as a notch filter, when needed or when more likely to be needed and selectively disable the noise filter(s) when no longer needed or unlikely to be needed. Accordingly, the techniques described herein may help mitigate the potential for increase in inappropriate shock rate for ICDs that are susceptible to noise while also minimizing current drain by active filter(s) to minimize a potential decrease in longevity of the ICD and minimizing conflicting interactions with other devices.

[0007] In one example, this disclosure describes a medical device comprising: a memory; and processing circuitry coupled to the memory, the processing circuitry is configured to: receive, from one or more electrodes coupled to the medical device, a cardiac signal of a patient; determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

[0008] In another example, this disclosure describes a medical system comprising: a medical device configured to sense a cardiac signal of a patient with at least one sensor; and processing circuitry configured to: determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

[0009] In another example, this disclosure describes a method comprising: receiving, from one or more electrodes coupled to a medical device, a cardiac signal of a patient; determining, by processing circuitry, an initial indication of a cardiac event based on the cardiac signal; determining, by processing circuitry, whether a particular feature of theAtly Ref. No: A0012209W001 cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activating, by the processing circuitry, a filter to filter noise from the cardiac signal.

[0010] 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 systems, devices, 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. Other features, objects, and advantages will be apparent from the description and drawings, and from the statements provided below.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 A is a front view of a patient with an extravascular ICD system implanted intra-thoracically.

[0012] FIG. IB is a side view of the patient with the extravascular ICD system implanted intra-thoracically.

[0013] FIG. 1C is a transverse view of the patient with the extravascular ICD system implanted intra-thoracically.

[0014] FIG. 2 is a functional block diagram of an example configuration of electronic components of an example ICD.

[0015] FIGS. 3 A-3D are flow diagrams illustrating example methods that may be performed by one or more medical devices to selectively activate a filter, in accordance with one or more techniques disclosed herein.

[0016] FIG. 4 is a flow diagram illustrating an example method that may be performed by one or more medical devices to selectively withhold therapy, in accordance with one or more techniques disclosed herein.DETAILED DESCRIPTION

[0017] Oversensing cardiac events, such as ventricular fibrillation (VF) or ventricular tachycardia (VT), may cause painful inappropriate shocks in patients with implantable cardioverter defibrillators (ICDs). For example, oversensing non-cardiac signals (e.g., noise and / or interference) and determining the noise and / or interference as VT or VF mayAtly Ref. No: A0012209W001 cause inappropriate shocks in patients with ICDs. Leads for ICDs, such as right ventricular (RV) leads, substemal leads, subcutaneous leads, or other extra-cardiac or extra- cardiovascular leads, are susceptible to picking up noise and / or interference, such as electromagnetic interference (EMI). In some examples, an integrated bipolar lead, e.g., in which a coil electrode or portion thereof is used as one of the electrodes of a bipolar sensing pair, may be more susceptible to noise and interference than a true bipolar lead because the distance between a tip electrode and a ring or sense electrode that are used for sensing is greater in an integrated bipolar lead than in a true bipolar lead.

[0018] EMI, for example, may cause false detections of ventricular depolarizations, which may result in false detections of VF or other ventricular tachyarrhythmia and subsequent unnecessary delivery of shocks or other therapeutic electrical signals to patients with HMDs. False ventricular depolarization detection may also lead to undesired inhibition of pacing therapy by IMDs. However, some IMDs may not reject EMI signals due to the need of high sensitivity for tachyarrhythmia sensing and detection. In some examples, a source of EMI a patient may encounter is from alternating current (AC) power sources. Some examples of frequencies of the EMI from those AC sources are 50 hertz (Hz) to 60Hz. In some examples, these EMI frequencies may be close enough to the bandpass range to be sensed after attenuation by device sensing amplifiers, which may be designed to reject higher frequency EMI sources in the modern environment. In addition, some IMDs may not reject EMI signals because filters have intensive current drain which negatively impacts battery life that may decrease the longevity of the IMD. In addition, filters may reduce sensitivity of sensing and detection by the IMD, and / or have conflicting feature interactions with other devices, such as sensing noise from other devices.

[0019] In general, this disclosure is directed to techniques that facilitate avoidance of oversensing due to noise without compromising detection sensitivity or battery life of the IMD. In accordance with the techniques of the disclosure, an IMD may be configured to selectively enable the noise filter(s), such as a notch filter, when needed or when more likely to be needed and selectively disable the noise filter(s) when no longer needed or unlikely to be needed. Accordingly, the techniques described herein may help mitigate the potential for increase in inappropriate shock rate for ICDs that are susceptible to noise while also controlling current drain due to active filters to control the decrease in longevity of the IMD and minimizing conflicting feature interactions with some devices.Atty Ref. No: A0012209W001

[0020] Although the noise detection techniques of this disclosure are primarily described herein with respect to detecting EMI, these techniques may be utilized to detect other types of noise. For example, the noise detection techniques of this disclosure may detect noise due to muscle or other motion artifacts, lead fractures or disconnections, magnetic resonance imaging, and other non-physiological noise. In some examples, the techniques described herein may be applied for detection of noise in ventricular electrograms to avoid inappropriate detection of ventricular tachyarrhythmia, e.g., VT or VF, atrial electrograms to avoid inappropriate detection of atrial tachyarrhythmia, e.g., atrial tachycardia, fibrillation, or flutter, and / or for detection of noise in surface el ectrocardi ogram s .

[0021] As used herein, relational terms, such as “first” and “second,” “over” and “under,” “front” and “rear,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.

[0022] Although the techniques of this disclosure are primarily described herein with respect to extravascular ICD system, these techniques may be utilized by a transvenous ICD system or any ICD system, a leadless pacemaker, such as the Micra™ leadless pacemaker, available from Medtronic, Inc., or any pacemaker, or any other HMD or IMD system that senses cardiac or other physiological signals that may be impacted by EMI or other noise sources.

[0023] FIGS. 1A-1C are conceptual diagrams illustrating an example medical device system 8 that may be used for sensing of physiological parameters of patient 12 and / or to provide therapy to heart 26 of patient 12. System 8 includes ICD 9, which is coupled to lead 10. While FIG. 1 A-1C shows ICD 9 coupled to lead 10, ICD 9 may also be coupled to a plurality of leads. ICD 9 may be, for example, an implantable pacemaker, cardioverter, and / or defibrillator that provides electrical signals to heart 26 via electrodes coupled to lead 10. Patient 12 is ordinarily, but not necessarily a human patient.

[0024] FIG. 1 A is a front view of a patient 12 implanted with extravascular ICD system 8 implanted intra-thoracically. Referring now to the drawings in which like reference designators refer to like elements, there is shown in FIGS. 1A-1C conceptual diagrams illustrating various views of an example extravascular ICD system 8. ICD system 8 includes an ICD 9 connected to an implantable medical lead 10. FIG. 1 A is aAtty Ref. No: A0012209W001 front view of a patient implanted with extravascular ICD system 8. FIG. IB is a side view of the patient implanted with extravascular ICD system 8. FIG. 1C is a transverse view of the patient implanted with extravascular ICD system 8.

[0025] ICD 9 may include a housing that forms a hermetic seal that protects components inside the ICD 9. The housing of ICD 9 may be formed of a conductive material, such as titanium or titanium alloy, which may function as a housing electrode (sometimes referred to as a can electrode). In some embodiments, ICD 9 may be formed to have or may include a plurality of electrodes on the housing. ICD 9 may also include a connector assembly 34 (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 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.

[0026] ICD 9 may be implanted extra-thoracically on the left side of the patient, e.g., under the skin and outside the ribcage (subcutaneously or submuscularly). ICD 9 may, in some instances, be implanted between the left posterior axillary line and the left anterior axillary line of the patient. ICD 9 may, however, be implanted at other extra-thoracic locations on the patient as described later.

[0027] 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 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 preformed and / or lead body 13 may be flexible to facilitate bending. In the example illustrated in FIGS. 1A-1C, the lead body 13 extends superiorly intra-thoracically underneath the sternum, in a direction substantially parallel to the sternum.

[0028] 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 substantiallyAty Ref. No: A0012209W001 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), adipose tissue, some lymph vessels, lymph glands, substemal musculature (e.g., transverse thoracic muscle), the thymus gland, branches of the internal thoracic arteries, and the internal thoracic veins (ITVs).

[0029] Lead body 13 may extend superiorly extra-thoracically (instead of intra- thoracically), e.g., either subcutaneously or submuscularly above the ribcage / sternum. 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 ITVs, 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.

[0030] 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.

[0031] 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 desiredAtty Ref. No: A0012209W001 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.

[0032] Lead body 13 may include a proximal portion 14 and a distal portion 16 which include 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, substernally 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 mesh-like elements and metallic or non- metallic scaffolds that facilitate tissue growth for engagement, bio-adhesive surfaces, and / or any other non-piercing elements.

[0033] Lead body 13 may define a substantially linear portion 20 (FIG. 1 A) as it curves or bends near the xiphoid process 23 and extends superiorly. In some examples, at least a part of distal portion 16 may define a three-dimensional undulating pattern, e.g., zig-zag, meandering, sinusoidal, serpentine, or other pattern, as it extends toward the distal end of lead 10.

[0034] 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 examples illustrated by FIGS. 1 A-1C, distal portion 16 includes two defibrillation electrodes 28a and 28b (collectively, “defibrillation electrodes 28”).

[0035] 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, molybdenum, stainless steel, MP35N, carbon, copper, polyaniline, polypyrrole, and otherAty Ref. No: A0012209W001 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.

[0036] 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, 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.

[0037] 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 pacing / sensing electrodes. In examples illustrated by FIGS. 1 A-1C, distal portion 16 includes two pacing / sensing electrodes 32a and 32b (collectively, “pacing / sensing electrodes 32”).

[0038] In some examples, electrodes 32 may be configured to deliver low-voltage electrical pulses to the heart and / 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 pacing / sensing electrodes 32. In 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, electrode segments extending circumferentially around less than half of a circumference of the lead body, 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 28Atly Ref. No: A0012209W001 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.

[0039] Electrodes 28 are referred to as defibrillation electrodes, and electrodes 32 are referred to as pacing / sensing electrodes, because they may have different physical structures enabling different functionality. Defibrillation electrodes 28 may be larger, e.g., have greater surface area, than pacing / sensing 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 pacing / sensing 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 pacing / sensing electrode 32. In some examples, sensing of electrical activity of the heart may be between sensing electrode 32b and all or a portion of one of defibrillation electrodes 28a, 28b.

[0040] Proximal portion 14 of lead body 13 may include one or more connectors 34 to electrically couple lead 10 to ICD 9. 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 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 ICD 9 may generate and deliver electrical therapy such as anti-tachycardia pacing, cardioversion or defibrillation shocks, post-shock pacing, and / or bradycardia pacing.

[0041] The three-dimensional 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 antitachyarrhythmia shocks may be delivered to the heart. The housing of ICD 9 may be charged with or function as a polarity different than the polarity of the one or moreAtly Ref. No: A0012209W001 defibrillation electrodes 28 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.

[0042] 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 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 pacing / sensing electrodes 32 or the housing electrode, to provide antitachyarrhythmia 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 ICD 9, to have the same polarity.

[0043] ICD 9 may be in wireless communication with another implanted medical device and / or may be in wireless communication with one or more patient computing device(s), e.g., patient computing device(s) 18. Patient computing device(s) 18 are configured for wireless communication with ICD 9. Computing device(s) 18 retrieve sensed physiological data from ICD 9 that was collected and stored by the ICD 9. In some examples, computing device(s) 18 take the form of personal computing devices of patient 12. For example, computing device(s) 18 may take the form of a smartphone of patient 12, a smartwatch or other smart apparel of patient 12. In some examples, computing device(s) 18 may be any computing device configured for wireless communication with ICD 9 such as a desktop, laptop, or tablet computer. Computing device(s) 18 may communicate with ICD 9 according to the Bluetooth® or Bluetooth® Low Energy (BLE) protocols, as examples. Computing device(s) 18 may be configured to communicate with a variety of other devices or systems via a network. For example, one or more of computing device(s) 18 may be configured to communicate with one or more computing systems that may be respectively managed by manufacturers of ICD 9 and computing device(s) 18 to, for example, provide cloud storage and analysis of collected data, maintenance and software services, or other networked functionality for their respectiveAtly Ref. No: A0012209W001 devices and users thereof. Computing system may comprise, or may be implemented by, the Medtronic CareLink™ Network, in some examples.

[0044] Although shown in FIG. 1 as a stand-alone device for purposes of example, computing device(s) 18 may be any component or system that includes processing circuitry or other suitable computing environment for executing software instructions and, for example, need not necessarily include one or more elements shown in FIG. 1.Computing device(s) 18 may include communication circuitry to communicate with other devices by transmitting and receiving data. In some examples, computing device(s) 18 may receive data from ICD 9, such as cardiac signals, noise, and / or interference, from communication circuitry in ICD 9. In some examples, cardiac signals may include noise, such as EMI. Computing device(s) may send data to ICD 9, such as data relating to noise / interference history or noise / interference episodes. Computing device(s) 18 may include a network interface card, such as an Ethernet card, an optical transceiver, a radio frequency transceiver, or any other type of device that can send and receive information. For example, computing device(s) 18 may include a radio transceiver configured for communication according to standards or protocols, such as 3G, 4G, 5G, Wi-Fi (e.g., 802.11 or 802.15 ZigBee), Bluetooth®, or Bluetooth® Low Energy (BLE).

[0045] The techniques of this disclosure may be applied to implantable systems other than ICD 9, including, but not limited to, bradycardia pacemaker systems, as well as with external stimulation devices, such as permanent or temporary external pacemakers or defibrillators.

[0046] In some examples, lead 10 may include a first defibrillation electrode 28a and a second defibrillation electrode 28b that are configured to deliver anti tachyarrhythmia shocks. In this example, pacing electrode 32b may be configured to deliver a pacing pulse that generates an electric field proximate to the pacing electrode.

[0047] As discussed above, in the examples of FIGS. 1 A-1C, lead 10 may sense electrical activity of heart 26, such as by electrodes 32 that may sense a cardiac electrical activity, e.g., depolarization and repolarization of the heart, and / or deliver electrical stimulation to heart 26., such as by defibrillation electrodes 28 and / or pacing / sensing electrodes 32.

[0048] FIG. 2 is a functional block diagram of an example configuration of electronic components and other components of ICD 9. ICD 9 includes a processing circuitry 202,Atly Ref. No: A0012209W001 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.

[0049] Sensing circuitry 204 may be electrically coupled to some or all of electrodes 216, which may correspond to any of the defibrillation, pacing / sensing, and housing electrodes described herein. Sensing circuitry 204 may be coupled to some or all of sensor(s) 208. Sensing circuitry 204 is configured to obtain signals sensed via one or more combinations of electrodes 216 and / or sensor(s) 208 and process the obtained signals. Sensing circuitry 204 may include filter 214. In some examples, sensing circuitry 204 may include a plurality of filters 214. In some examples, sensing circuitry 204 may be implemented in the processing circuitry 202 of ICD 9.

[0050] 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. Sensing 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, ICD 9 may additionally include one or more sensors 208, such as one or more accelerometers or bioimpedance sensors, which may be configured to provide signals indicative of other parameters of a patient, such as activity, posture, or subcutaneous impedance to processing circuitry 202.Atty Ref. No: A0012209W001

[0051] Processing circuitry 202 may process the signals from sensing circuitry 204 to monitor electrical activity of heart 26 of patient 12. Processing circuitry 202 may store signals obtained by sensing circuitry 204 as well as any generated electrogram (EGM) 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 arrhythmias (e.g., bradycardia or tachycardia).

[0052] In response to detecting a cardiac event, processing circuitry 202 may control therapy delivery circuitry 206 to deliver the desired therapy to treat the cardiac event, e.g., defibrillation shock, cardioversion shock, ATP, post shock pacing, or bradycardia pacing.

[0053] 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, defibrillation therapy, 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 of electrodes 216. Although not shown in FIG. 2, 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.

[0054] Processing circuitry 202 may receive from one or more sensing electrodes 32, coupled to ICD 9, one or more cardiac signals of patient 12. In some examples, the one or more cardiac signals may additionally include noise, such as EMI. In some examples, the one or more sensing electrodes may be in positioned in a lead coupled to an ICD or be positioned in a leadless ICD. Processing circuitry 202 may also receive noise from one or more sensing electrodes 32. In some examples, the cardiac signals may be corrupted by the noise. In some examples, the noise corrupting the cardiac signals may cause falseAtly Ref. No: A0012209W001 detections of ventricular depolarizations and / or ventricular fibrillation (VF), and may result in subsequent unnecessary delivery of shocks by ICD 9.

[0055] Processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, based on the cardiac signal. For example, processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, occurred based a particular amount of VF or VT senses occurring in a cardiac signal during a period of time satisfying an initial indication of cardiac event threshold. In some examples, processing circuitry 202 may determine an initial indication of a cardiac event occurred while a filter 214, such as a notch filter, is disabled / deactivated. In some examples, processing circuitry 202 may determine an initial indication of a cardiac event based on signals received from sensors 208, such as bioimpedance sensors, in ICD 9. Processing circuitry 202 may determine whether a particular feature of the cardiac signal satisfies a filter threshold. In some examples, a filter threshold value may be based on whether the cardiac signal is sensed via an integrated bipolar electrode pair (e.g., in which a coil electrode or portion thereof is used as one of the electrodes of a bipolar sensing pair) or via a true bipolar electrode pair. In response to the particular feature of the cardiac signal satisfying the filter threshold, processing circuitry 202 may activate a filter 214, such as a notch filter, to filter noise from the cardiac signal. In some examples, processing circuitry 202 may automatically activate filter 214 in response to the particular feature of the cardiac signal satisfying the filter threshold. In some examples, processing circuitry 202 may apply the cardiac signal to the activated filter 214 to generate a filtered cardiac signal. In some examples, processing circuitry 202 may determine whether the filtered cardiac signal indicates a cardiac event, such as VF or VT. In some examples, in response to a determination that the filtered cardiac signal indicates the cardiac event, such as VF or VT, processing circuitry 202 may disable / deactivate the filter 214 to prevent or reduce under sensing of cardiac events. In some examples, in response to a determined that the filtered cardiac signal does not indicate the cardiac event, such as VF or VT, processing circuitry 202 may determine the initial indication of the cardiac event is noise. In some examples, in response to a determination that the initial indication of the cardiac event is noise, processing circuitry 202 may disable / deactivate the filter 214. In some examples, processing circuitry 202 may automatically disable / deactivate the filter 214 in response to a determination that the initial indication of the cardiac event is noise.Atty Ref. No: A0012209W001

[0056] In some examples, a particular feature of the cardiac signal satisfying the filter threshold may indicate a heart of patient 12 is beating at a “normal” rhythm. In some examples, the particular feature may include a morphology of the cardiac signal or an amplitude of the cardiac signal. In some examples, processing circuitry 202 may determine a particular morphology and / or a particular amplitude of the cardiac signal satisfies a filter threshold based on the particular morphology and / or a particular amplitude of the cardiac signal satisfying a respective filter threshold. In some examples, processing circuitry 202 may determine a particular morphology and / or a particular amplitude of the cardiac signal satisfies a filter threshold based on the particular morphology and / or a particular amplitude of the cardiac signal indicating a heart of the patient is beating at a normal rhythm (e.g., a sinus rhythm). In some examples, processing circuitry 202 may determine a particular morphology and / or a particular amplitude of the cardiac signal satisfies a filter threshold based on the particular morphology and / or a particular amplitude of the cardiac signal indicating one or more R-waves. In response to a particular morphology and / or a particular amplitude of the cardiac signal satisfying the filter threshold, processing circuitry 202 may activate a filter 214, such as a notch filter, to filter noise from the cardiac signal. In some examples, processing circuitry 202 may activate filter 214 during one or more R-R intervals of the cardiac intervals. For example, processing circuitry 202 may determine one or more R-R intervals of the cardiac signal and activate and apply filter 214 to the one or more R-R intervals of the cardiac signal. In some examples, processing circuitry 202 may activate filter 214 between R-R intervals of the cardiac intervals. For example, processing circuitry 202 may determine one or more R-R intervals of the cardiac signal and activate and apply filter 214 after the R-R interval of the cardiac signal and before the following R-R interval (e.g., between R-R intervals of the cardiac signal).

[0057] In some examples, the particular feature of the cardiac signal may include an interval length of the cardiac signal. In some examples, the particular feature of the cardiac signal may include a peak-to-peak interval length of the cardiac signal. In some examples, the particular feature may include another cardiac cycle interval length or another interval length between two points of the cardiac signal.

[0058] In some examples, processing circuitry 202 may determine an interval length and / or a peak-to-peak interval length of the cardiac signal satisfies a filter threshold basedAty Ref. No: A0012209W001 on the interval length and / or peak-to-peak interval length satisfying a particular respective interval length threshold. In some examples, the interval length threshold may be between 100 milliseconds (ms) and 160 ms. In some examples, the interval length threshold may be between 15 ms and 160 ms. In some examples, the interval length threshold may be between 8 ms and 160 ms. In some examples, an interval length and / or peak-to-peak interval length satisfying a particular respective interval length threshold may indicate that the initial indication of the cardiac event may be noise. In some examples, in response to determination that an interval length and / or a peak-to-peak interval length of the cardiac signal satisfies a filter threshold, processing circuitry 202 may activate a filter 214, such as a notch filter, to filter noise from the cardiac signal. In some examples, processing circuitry 202 may determine whether filtered cardiac signal indicates a cardiac event, such as VF or VT. In some examples, in response to a determination that the filtered cardiac signal indicates a cardiac event, such as VF or VT, processing circuitry may determine the initial indication of a cardiac event was not due to noise and / or deactivate / disable filter 214 to prevent or reduce under sensing of a cardiac event, such as VF or VT. In some examples, an interval length and / or peak-to-peak interval length satisfying a particular respective interval length threshold may correspond to an increased likelihood the initial indication of the cardiac event was due to noise and processing circuitry 202 activating filter 214 during these particular times of increased likelihood the initial indication of the cardiac event was due to noise may reduce time that filter 214, such as a notch filter, is activated, which may reduce power usage by ICD 9.

[0059] In some examples, the particular feature of the cardiac signal may include a number of consecutive intervals of the cardiac signal satisfying an interval length criterion. In some examples, processing circuitry 202 may determine a number of consecutive intervals of the cardiac signal satisfying an interval length criterion satisfies a consecutive interval threshold satisfying the interval length criterion. In some examples, an interval length criterion may be between 100 ms and 160 ms. In some examples, the interval length criterion may be between 15 ms and 160 ms. In some examples, the interval length criterion may be between 8 ms and 160 ms. In some examples, the consecutive interval threshold may be at least three consecutive intervals. For example, the consecutive interval threshold may be satisfied when the cardiac signal includes at least three consecutive intervals having an interval length between 100 ms and 160 ms. In some examples, theAtly Ref. No: A0012209W001 intervals may be peak-to-peak intervals. In some examples, in response to a determination that a number of consecutive intervals of the cardiac signal satisfying an interval length criterion, such as between 100 ms and 160 ms, satisfies a consecutive interval threshold, processing circuitry 202 may activate a filter 214, such as a notch filter, to filter noise from the cardiac signal. In some examples, processing circuitry 202 may determine whether filtered cardiac signal indicates a cardiac event, such as VF or VT. In some examples, in response to a determination that the filtered cardiac signal indicates a cardiac event, such as VF or VT, processing circuitry may determine the initial indication of a cardiac event was not due to noise and / or deactivate / disable filter 214 to prevent or reduce under sensing of a cardiac event, such as VF or VT. In some examples, a number of consecutive intervals of the cardiac signal satisfying an interval length criterion, such as between 100 ms and 160 ms, satisfying a consecutive interval threshold may correspond to an increased likelihood the initial indication of the cardiac event was due to noise and processing circuitry 202 activating filter 214 during these particular times of increased likelihood the initial indication of the cardiac event was due to noise may reduce time that filter 214, such as a notch filter, is activated during periods of low noise, which may reduce power usage by ICD 9.

[0060] In some examples, filter 214 may have intensive current drain which may negatively impact battery life when filter 214 is activated that may decrease the longevity of ICD 9. Accordingly, selectively activating filter 214 in accordance with the techniques described herein may help reduce unnecessary delivery of shocks by ICD 9 while minimizing the effect activating filter 214 has on the battery life of ICD 9.

[0061] In some examples, very high levels of noise, such as EMI, may cause oversensing even with a notch filter activated. In some examples, after activating filter 214 in accordance with any of the techniques described herein, processing circuitry 202 may apply the cardiac signal to filter 214 to generate a filtered cardiac signal. In some examples, processing circuitry 202 may determine a difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal. In some examples, processing circuitry 202 may determine whether the difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal satisfies a therapy withholding threshold. In some examples, in response to a determination that the difference between an amplitude of the cardiac signal and an amplitude of the filteredAtly Ref. No: A0012209W001 cardiac signal satisfies the therapy withholding threshold, processing circuitry 202 may output an indication to ICD 9 to withhold therapy for a period of time.

[0062] In some examples, in response to determining an initial indication of a cardiac event is a confirmed cardiac event, processing circuitry 202 may control therapy delivery circuitry 206 to deliver the desired therapy to treat the cardiac event, e.g., defibrillation shock, cardioversion shock, ATP, post shock pacing, or bradycardia pacing.

[0063] 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, defibrillation therapy, 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 of electrodes 216. Although not shown in FIG. 2, 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. In some examples, in response to a determination that the difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal satisfies the therapy withholding threshold, processing circuitry 202 may output an indication to therapy delivery circuitry 206 to withhold therapy for a period of time.

[0064] 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.Atly Ref. No: A0012209W001

[0065] The various components of 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.

[0066] Memory 212 may include computer-readable instructions that, when executed by processing circuitry 202 or other components of ICD 9, cause one or more components of 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.

[0067] FIGS. 3 A-3D are flow diagrams illustrating example techniques of selectively activating / deactivating a filter, such as a notch filter, to filter noise, such as EMI, from a cardiac signal in accordance with ICD 9, as shown in FIG. 2. In some examples, as shown in FIG. 3 A, processing circuitry 202 may receive, from one or more sensing electrodes 32 coupled to a medical device, one or more cardiac signals (302). In some examples, processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, based on the cardiac signal (304). In some examples, processing circuitry 202 may determine whether a particular feature of the cardiac signal satisfies a filter threshold (306). In some examples, in response to a determination that a particular feature of the cardiac signal does not satisfy a filter threshold (“NO”), processing circuitry 202 may return to feature (302). In some examples, in response to a determination that a particular feature of the cardiac signal satisfies a filter threshold (“YES”), processing circuitry 202 may activate filter 214 (308). In some examples, filter 214 may be a notch filter. In some examples, processing circuitry 202 may apply the cardiac signal to activated filter 214 (310). In some examples, processing circuitry 202 may determine whether the filtered cardiac signal indicated the cardiac event, such as VF or VT, occurred (312). In response to a determination that the filtered cardiac signal indicates the cardiac event occurred (“YES”), processing circuitry 202 may disable / deactivate filter 214 (314). In response to aAtly Ref. No: A0012209W001 determination that the filtered cardiac signal does not indicate the cardiac event occurred (“NO”), processing circuitry 202 may return to feature (310) and apply additional cardiac signal(s) to the activated filter 214 for a period of time. In some examples, in response to filter 214 being on for a period time that satisfies a filter activation time threshold, processing circuitry 202 may deactivate filter 214 and return to feature (302).

[0068] In some examples, as shown in FIG. 3B, processing circuitry 202 may receive, from one or more sensing electrodes 32 coupled to a medical device, one or more cardiac signals (322). In some examples, processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, based on the cardiac signal (324). In some examples, processing circuitry 202 may determine whether a morphology or an amplitude of the cardiac signal indicates one or more R-waves in the cardiac signal (326). In some examples, a morphology or an amplitude of the cardiac signal indicating one or more R-waves in the cardiac signal may correspond to a morphology or an amplitude of the cardiac signal satisfying a filter threshold. In some examples, in response to a determination that a morphology or an amplitude of the cardiac signal does not indicate one or more R-waves in the cardiac signal (“NO”), processing circuitry 202 may return to feature (322). In some examples, in response to a determination that a morphology or an amplitude of the cardiac signal indicates one or more R-waves in the cardiac signal (“YES”), processing circuitry 202 may activate filter 214 (328). In some examples, filter 214 may be a notch filter. In some examples, processing circuitry 202 may apply the cardiac signal to activated filter 214 (330). In some examples, processing circuitry 202 may determine whether the filtered cardiac signal indicated the cardiac event, such as VF or VT, occurred (332). In response to a determination that the filtered cardiac signal indicates the cardiac event occurred (“YES”), processing circuitry 202 may disable / deactivate filter 214 (334). In response to a determination that the filtered cardiac signal does not indicate the cardiac event occurred (“NO”), processing circuitry 202 may return to feature (330) and apply additional cardiac signal(s) to the activated filter 214 for a period of time. In some examples, in response to filter 214 being on for a period time that satisfies a filter activation time threshold, processing circuitry 202 may deactivate filter 214 and return to feature (322).

[0069] In some examples, as shown in FIG. 3C, processing circuitry 202 may receive, from one or more sensing electrodes 32 coupled to a medical device, one or more cardiacAtly Ref. No: A0012209W001 signals (342). In some examples, processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, based on the cardiac signal (344). In some examples, processing circuitry 202 may determine whether an interval length of the cardiac signal satisfies an interval length threshold (346). In some examples, an interval length of the cardiac signal satisfying an interval length threshold may correspond to an interval length of the cardiac signal satisfying a filter threshold. In some examples, an interval length of the cardiac signal may be a peak-to-peak interval length. In some examples, an interval length threshold is between 100 ms and 160 ms. In some examples, in response to a determination that an interval length of the cardiac signal does not satisfy an interval length threshold (“NO”), processing circuitry 202 may return to feature (342). In some examples, in response to a determination that an interval length of the cardiac signal satisfies an interval length threshold (“YES”), processing circuitry 202 may activate filter 214 (348). In some examples, filter 214 may be a notch filter. In some examples, processing circuitry 202 may apply the cardiac signal to activated filter 214 (350). In some examples, processing circuitry 202 may determine whether the filtered cardiac signal indicated the cardiac event, such as VF or VT, occurred (352). In response to a determination that the filtered cardiac signal indicates the cardiac event occurred (“YES”), processing circuitry 202 may disable / deactivate filter 214 (354). In response to a determination that the filtered cardiac signal does not indicate the cardiac event occurred (“NO”), processing circuitry 202 may return to feature (350) and apply additional cardiac signal(s) to the activated filter 214 for a period of time. In some examples, in response to filter 214 being on for a period time that satisfies a filter activation time threshold, processing circuitry 202 may deactivate filter 214 and return to feature (342).

[0070] In some examples, as shown in FIG. 3D, processing circuitry 202 may receive, from one or more sensing electrodes 32 coupled to a medical device, one or more cardiac signals (362). In some examples, processing circuitry 202 may determine an initial indication of a cardiac event, such as VF or VT, based on the cardiac signal (364). In some examples, processing circuitry 202 may determine whether a number of consecutive intervals having a particular length satisfies a consecutive interval threshold satisfying an interval length criterion (366). In some examples, an interval length of the cardiac signal satisfying an interval length threshold may correspond to an interval length of the cardiac signal satisfying a filter threshold. In some examples, the interval length of the cardiacAtly Ref. No: A0012209W001 signal may be between two similar points of the cardiac signal, such as a peak-to-peak interval length. In some examples, the interval length criterion of the cardiac signal may be between 100 ms and 160 ms. In some examples, the consecutive interval threshold is at least three consecutive intervals. In some examples, the consecutive interval threshold is at least three consecutive intervals having an interval length between 100 ms and 160 ms. In some examples, in response to a determination that a number of consecutive intervals having a particular length does not satisfy a consecutive interval threshold satisfying an interval length criterion (“NO”), processing circuitry 202 may return to feature (362). In some examples, in response to a determination that a number of consecutive intervals having a particular length satisfies a consecutive interval threshold satisfying an interval length criterion (“YES”), processing circuitry 202 may activate filter 214 (368). In some examples, filter 214 may be a notch filter. In some examples, processing circuitry 202 may apply the cardiac signal to activated filter 214 (370). In some examples, processing circuitry 202 may determine whether the filtered cardiac signal indicated the cardiac event, such as VF or VT, occurred (372). In response to a determination that the filtered cardiac signal indicates the cardiac event occurred (“YES”), processing circuitry 202 may disable / deactivate filter 214 (374). In response to a determination that the filtered cardiac signal does not indicate the cardiac event occurred (“NO”), processing circuitry 202 may return to feature (370) and apply additional cardiac signal(s) to the activated filter 214 for a period of time. In some examples, in response to filter 214 being on for a period time that satisfies a filter activation time threshold, processing circuitry 202 may deactivate filter 214 and return to feature (362).

[0071] In some examples, very high levels of noise, such as EMI, may cause oversensing even with a notch filter activated. FIG. 4 is a flow diagram illustrating an example technique of withholding therapy by ICD 9 for a period of time. In some examples, as shown in FIG. 4, after activating filter 214 in accordance with any of the techniques described herein, processing circuitry 202 may apply the cardiac signal to filter 214 to generate a filtered cardiac signal (402). In some examples, processing circuitry 202 may determine a difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal (404). In some examples, processing circuitry 202 may determine whether the difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal satisfies a therapy withholding threshold (406). InAtly Ref. No: A0012209W001 some examples, in response to a determination that the difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal satisfies the therapy withholding threshold (“YES”), processing circuitry 202 may output an indication to ICD 9 to withhold therapy for a period of time (408), which may result in a reduction of unnecessary delivery of shocks by ICD 9. In some examples, in response to a determination that the difference between an amplitude of the cardiac signal and an amplitude of the filtered cardiac signal does not satisfy the therapy withholding threshold (“NO”), processing circuitry 202 may disable / deactivate filter 214 (410).

[0072] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module, unit, or circuit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units, modules, or circuitry associated with, for example, a medical device.

[0073] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0074] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” or “processing circuitry” as used herein may refer to any of the foregoing structure or any other physicalAty Ref. No: A0012209W001 structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0075] The following examples are illustrative of the techniques described herein.

[0076] Example 1 : A medical device includes a memory; and processing circuitry coupled to the memory, the processing circuitry is configured to: receive, from one or more electrodes coupled to the medical device, a cardiac signal of a patient; determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

[0077] Example 2: The medical device of example 1, wherein the particular feature of the cardiac signal satisfying the filter threshold indicates a heart of the patient is beating at a normal rhythm.

[0078] Example 3: The medical device of any of examples 1-2, wherein the particular feature of the cardiac signal includes a morphology or an amplitude of the cardiac signal.

[0079] Example 4: The medical device of example 3, wherein the filter threshold includes the morphology or the amplitude of the cardiac signal indicating one or more Il- wave s.

[0080] Example 5: The medical device of example 4, wherein the processing circuitry is further configured to activate the filter between R-R intervals of the cardiac signal.

[0081] Example 6: The medical device of example 1, wherein the particular feature of the cardiac signal includes an interval length of the cardiac signal.

[0082] Example 7: The medical device of example 1, wherein the particular feature of the cardiac signal includes a peak-to-peak interval length of the cardiac signal.

[0083] Example 8: The medical device of example 1, wherein the particular feature of the cardiac signal includes a cardiac cycle interval length or an interval length between two points of the cardiac signal.

[0084] Example 9: The medical device of any of examples 6-8, wherein the filter threshold includes an interval length threshold.

[0085] Example 10: The medical device of example 9, wherein the interval length threshold is between 100 milliseconds (ms) and 160 ms.Atly Ref. No: A0012209W001

[0086] Example 11 : The medical device of example 1, wherein the particular feature of the cardiac signal includes a number of consecutive intervals of the cardiac signal satisfying an interval length criterion.

[0087] Example 12: The medical device of example 11, wherein the filter threshold includes a consecutive interval threshold satisfying the interval length criterion.

[0088] Example 13: The medical device of example 12, wherein the interval length criterion is between 100 milliseconds (ms) and 160 ms and the consecutive interval threshold is three consecutive intervals having an interval length between 100 ms and 160 ms.

[0089] Example 14: The medical device of any of examples 1-13, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine whether the filtered cardiac signal indicates the cardiac event; and in response to a determination that the filtered cardiac signal indicates the cardiac event, disable the filter.

[0090] Example 15: The medical device of any of examples 1-13, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine a difference between an amplitude of the cardiac signal and an amplitude the filtered cardiac signal; determine whether the difference satisfies a therapy withholding threshold; and in response to a determination that the difference satisfies the therapy withholding threshold, output an indication to the medical device to withhold therapy for a period of time.

[0091] Example 16: The medical device of any of examples 1-13, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; detect a tachyarrhythmia based on the filtered cardiac signal; and deliver a tachyarrhythmia shock in response to detecting the tachyarrhythmia.

[0092] Example 17: The medical device of any of examples 1-16, wherein the filter is a notch filter.

[0093] Example 18: The medical device of any of examples 1-17, wherein the medical device is an implantable cardioverter defibrillator.

[0094] Example 19: A medical device system includes a medical device configured to sense a cardiac signal of a patient with at least one sensor; and processing circuitry configured to: determine an initial indication of a cardiac event based on the cardiacAty Ref. No: A0012209W001 signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

[0095] Example 20: The medical device system of example 19, wherein the particular feature of the cardiac signal satisfying the filter threshold indicates a heart of the patient is beating at a normal rhythm.

[0096] Example 21 : The medical device system of any of examples 19-20, wherein the particular feature of the cardiac signal includes a morphology or an amplitude of the cardiac signal.

[0097] Example 22: The medical device system of example 21, wherein the filter threshold includes the morphology or the amplitude of the cardiac signal indicating one or more R-waves.

[0098] Example 23 : The medical device system of example 22, wherein the processing circuitry is further configured to activate the filter between R-R intervals of the cardiac signal.

[0099] Example 24: The medical device system of example 19, wherein the particular feature of the cardiac signal includes an interval length of the cardiac signal.

[0100] Example 25: The medical device system of example 19, wherein the particular feature of the cardiac signal includes a peak-to-peak interval length of the cardiac signal.

[0101] Example 26: The medical device system of example 19, wherein the particular feature of the cardiac signal includes a cardiac cycle interval length or an interval length between two points of the cardiac signal.

[0102] Example 27: The medical device system of any of examples 24-26, wherein the filter threshold includes an interval length threshold.

[0103] Example 28: The medical device system of example 27, wherein the interval length threshold is between 100 milliseconds (ms) and 160 ms.

[0104] Example 29: The medical device system of example 19, wherein the particular feature of the cardiac signal includes a number of consecutive intervals of the cardiac signal satisfying an interval length criterion.

[0105] Example 30: The medical device system of example 29, wherein the filter threshold includes a consecutive interval threshold satisfying the interval length criterion.Atly Ref. No: A0012209W001

[0106] Example 31 : The medical device system of example 30, wherein the interval length criterion is between 100 milliseconds (ms) and 160 ms and the consecutive interval threshold is at least three consecutive intervals having an interval length between 100 ms and 160 ms.

[0107] Example 32: The medical device system of any of examples 19-31, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine whether the filtered cardiac signal indicates the cardiac event; and in response to a determination that the filtered cardiac signal indicates the cardiac event, disable the filter.

[0108] Example 33: The medical device system of any of examples 19-31, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine a difference between an amplitude of the cardiac signal and an amplitude the filtered cardiac signal; determine whether the difference satisfies a therapy withholding threshold; and in response to a determination that the difference satisfies the therapy withholding threshold, output an indication to the medical device to withhold therapy for a period of time.

[0109] Example 34: The medical device system of any of examples 19-31, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; detect a tachyarrhythmia based on the filtered cardiac signal; and deliver a tachyarrhythmia shock in response to detecting the tachyarrhythmia.

[0110] Example 35: The medical device system of any of examples 19-34, wherein the filter is a notch filter.

[0111] Example 36: The medical device system of any of examples 19-35, wherein the medical device is an implantable cardioverter defibrillator.

[0112] Example 37: A method includes receiving, from one or more electrodes coupled to a medical device, a cardiac signal of a patient; determining, by processing circuitry, an initial indication of a cardiac event based on the cardiac signal; determining, by processing circuitry, whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activating, by the processing circuitry, a filter to filter noise from the cardiac signal.Atly Ref. No: A0012209W001

[0113] Example 38: The method of example 37, wherein the particular feature of the cardiac signal satisfying the filter threshold indicates a heart of the patient is beating at a normal rhythm.

[0114] Example 39: The method any of examples 37-38, wherein the particular feature of the cardiac signal includes a morphology or an amplitude of the cardiac signal.

[0115] Example 40: The method of example 39, wherein the filter threshold includes the morphology or the amplitude of the cardiac signal indicating one or more R-waves.

[0116] Example 41 : The method of example 40, wherein the processing circuitry is further configured to activate the filter between R-R intervals of the cardiac signal.

[0117] Example 42: The method of example 37, wherein the particular feature of the cardiac signal includes an interval length of the cardiac signal.

[0118] Example 43 : The method of example 37, wherein the particular feature of the cardiac signal includes a peak-to-peak interval length of the cardiac signal.

[0119] Example 44: The method of example 37, wherein the particular feature of the cardiac signal includes a cardiac cycle interval length or an interval length between two points of the cardiac signal.

[0120] Example 45: The method of any of examples 42-44, wherein the filter threshold includes an interval length threshold.

[0121] Example 46: The method of example 45, wherein the interval length threshold is between 100 milliseconds (ms) and 160 ms.

[0122] Example 47: The method of example 37, wherein the particular feature of the cardiac signal includes a number of consecutive intervals of the cardiac signal satisfying an interval length criterion.

[0123] Example 48: The method of example 47, wherein the filter threshold includes a consecutive interval threshold having the interval length criterion.

[0124] Example 49: The method of example 48, wherein the interval length criterion is between 100 milliseconds (ms) and 160 ms and the consecutive interval threshold is at least three consecutive intervals having an interval length between 100 ms and 160 ms.

[0125] Example 50: The method of any of examples 37-49, the method further includes applying, by the processing circuitry, the cardiac signal to the activated filter to generate a filtered cardiac signal; determining, by the processing circuitry, whether the filtered cardiac signal indicates the cardiac event; and in response to a determination thatAtly Ref. No: A0012209W001 the filtered cardiac signal indicates the cardiac event, disabling, by the processing circuitry, the filter.

[0126] Example 51 : The method of any of examples 37-49, the method further includes applying, by the processing circuitry, the cardiac signal to the activated filter to generate a filtered cardiac signal; determining, by the processing circuitry, a difference between an amplitude of the cardiac signal and an amplitude the filtered cardiac signal; determining, by the processing circuitry, whether the difference satisfies a therapy withholding threshold; and in response to a determination that the difference satisfies the therapy withholding threshold, outputting, by the processing circuitry, an indication to the medical device to withhold therapy for a period of time.

[0127] Example 52: The method of any of examples 37-49, the method further includes applying, by the processing circuitry, the cardiac signal to the activated filter to generate a filtered cardiac signal; detecting, by the processing circuitry, a tachyarrhythmia based on the filtered cardiac signal; and delivering, by the processing circuitry via one or more electrodes of the medical device, a tachyarrhythmia shock in response to detecting the tachyarrhythmia.

[0128] Example 53: The method of any of examples 37-52, wherein the filter is a notch filter.

[0129] Example 54: The method of any of examples 37-53, wherein the medical device is an implantable cardioverter defibrillator.

[0130] It will be appreciated by persons skilled in the art that the present application is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the application, which is limited only by the following claims.

Claims

Atly Ref. No: A0012209W001WHAT IS CLAIMED IS:

1. A medical device comprising: a memory; and processing circuitry coupled to the memory, the processing circuitry is configured to: receive, from one or more electrodes coupled to the medical device, a cardiac signal of a patient; determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

2. The medical device of claim 1, wherein the particular feature of the cardiac signal satisfying the filter threshold indicates a heart of the patient is beating at a normal rhythm.

3. The medical device of any of claims 1-2, wherein the particular feature of the cardiac signal includes a morphology or an amplitude of the cardiac signal.

4. The medical device of claim 3, wherein the filter threshold includes the morphology or the amplitude of the cardiac signal indicating one or more R-waves.

5. The medical device of claim 4, wherein the processing circuitry is further configured to activate the filter between R-R intervals of the cardiac signal.

6. The medical device of claim 1, wherein the particular feature of the cardiac signal includes an interval length of the cardiac signal.Atly Ref. No: A0012209W0017. The medical device of claim 1, wherein the particular feature of the cardiac signal includes a peak-to-peak interval length of the cardiac signal.

8. The medical device of claim 1, wherein the particular feature of the cardiac signal includes a cardiac cycle interval length or an interval length between two points of the cardiac signal.

9. The medical device of any of claims 1-8, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine whether the filtered cardiac signal indicates the cardiac event; and in response to a determination that the filtered cardiac signal indicates the cardiac event, disable the filter.

10. The medical device of any of claims 1-9, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine a difference between an amplitude of the cardiac signal and an amplitude the filtered cardiac signal; determine whether the difference satisfies a therapy withholding threshold; and in response to a determination that the difference satisfies the therapy withholding threshold, output an indication to the medical device to withhold therapy for a period of time.

11. The medical device of any of claims 1-9, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; detect a tachyarrhythmia based on the filtered cardiac signal; and deliver a tachyarrhythmia shock in response to detecting the tachyarrhythmia.Atly Ref. No: A0012209W00112. A medical device system comprising: a medical device configured to sense a cardiac signal of a patient with at least one sensor; and processing circuitry configured to: determine an initial indication of a cardiac event based on the cardiac signal; determine whether a particular feature of the cardiac signal satisfies a filter threshold; and in response to the particular feature of the cardiac signal satisfying the filter threshold, activate a filter to filter noise from the cardiac signal.

13. The medical device system of claim 12, wherein the particular feature of the cardiac signal includes a morphology or an amplitude of the cardiac signal.

14. The medical device system of any of claims 12-13, wherein the processing circuitry is further configured to activate the filter between R-R intervals of the cardiac signal.

15. The medical device system of any of claims 12-14, wherein the processing circuitry is further configured to: apply the cardiac signal to the activated filter to generate a filtered cardiac signal; determine whether the filtered cardiac signal indicates the cardiac event; and in response to a determination that the filtered cardiac signal indicates the cardiac event, disable the filter.

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