Reducing far-field oversensing via integrated bipolar lead

Abstract

An example system includes an implantable medical device (IMD) configured to: obtain an integrated bipolar electrogram (EGM) signal of first chamber of a heart sensed via a first lead implanted in the first chamber; and at least one of: identify an intrinsic event of a second chamber of the heart sensed via a second lead implanted in the second chamber; or identify a paced event of the second chamber sensed via the second lead; processing circuitry configured to: generate a time window of the EGM signal based on one or more of the identified intrinsic event or the identified paced event; determine a value of feature(s) of the EGM signal during the time window; determine the value of the feature(s) satisfies a far-field activity threshold; and based on determining the value of the feature(s) satisfies the far-field activity threshold, adjust a sensitivity threshold of the IMD.

Description

REDUCING FAR-FIELD OVERSENSING VIA INTEGRATED BIPOLAR LEAD

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 593,655, filed October 27, 2023, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

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

[0003] Some types of implantable medical devices, such as cardiac pacemakers or implantable cardioverter defibrillators, provide electrical therapy to a heart of a patient via electrodes of one or more implantable leads. The electrical therapy may be delivered to the heart in the form of pulses for pacing or shocks for cardioversion or defibrillation. In some cases, an implantable medical device may sense intrinsic depolarizations of the heart and control the delivery of electrical therapy to the heart based on the sensing.SUMMARY

[0004] In general, this disclosure describes example techniques related to adjusting a sensitivity threshold to prevent or reduce a likelihood of an integrated bipolar lead in a multi-chamber system (e.g., a system that includes leads implanted within multiple chambers of the heart) from oversensing far-field activity. The integrated bipolar lead may comprise an integrated bipolar lead implanted within the ventricle and the techniques of this disclosure could be utilized to reduce oversensing atrial far-field activity. For example, an implantable medical system may include an implantable medical device (IMD), such as a pacemaker, an implantable cardioverter defibrillator (ICD) or implantable cardiac resynchronization therapy (CRT), that is coupled to a ventricular integrated bipolar lead configured to be implanted in a ventricle of a heart of a patient, and be configured to sense ventricular cardiac electrogram (EGM) signals of a patient via the ventricular integrated bipolar lead. The implantable medical system may further be coupled to an atrial lead configured to be implanted in an atrium of the patient, and be configured to sense atrialcardiac EGM signals of the patient via the atrial lead. The IMD may identify an atrial intrinsic event (e.g., depolarization) and / or or an indication of an atrial paced event on the patient based on the atrial cardiac EGM signal from the atrial lead.

[0005] The IMD may be configured to generate a time window of the ventricular EGM signal based on a timing of one or more of the atrial intrinsic event or the atrial paced event. The IMD may determine a value of one or more features of the ventricular EGM signal during the time window and determine whether the value of the one or more features of the ventricular EGM signal satisfies a far-field activity threshold. In response to the value of the one or more features of the ventricular EGM signal satisfying a far-field activity threshold of the ventricle integrated bipolar lead, IMD may adjust the sensitivity threshold of the ventricle integrated bipolar lead, such as increasing the sensitivity threshold, to reduce a likelihood of subsequent instances of atrial oversensing, such as P-wave oversensing, in the ventricular EGM signal. In some examples, generating the time window based on one or more of the sensed atrial event or the atrial paced event may focus the determined values of one or more features of the EGM signal to be during the period of time (e.g. time window) in which atrial heart activity and / or atrial sensing is occurring, which may help isolate and indicate features that could lead to atrial oversensing, such as P-wave oversensing, by the ventricular integrated bipolar lead.

[0005] In one example, this disclosure describes a system comprising: an implantable medical device (IMD) configured to: obtain an integrated bipolar electrogram (EGM) signal of first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; and at least one of: identify an intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber; or identify a paced event of the second chamber sensed via the second lead; processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the IMD from a first value to a second value.

[0006] In another example, this disclosure describes implantable medical device comprising: sensing circuitry configured to: obtain an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber, wherein the first lead comprises an integrated bipolar lead; and identify an intrinsic event of a second chamber of the heart sensed via a second lead implanted in the second chamber; therapy delivery circuitry configured to perform a paced event on the second chamber of the heart via the second lead; and processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the sensing circuitry from a first value to a second value.

[0007] In another example, this disclosure describes a method comprising: receiving an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; receiving at least one of an identified intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber or an identified paced event of the second chamber sensed via the second lead; generating a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determining a value of one or more features of the integrated bipolar EGM signal during the time window; determining the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and in response to determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of an implantable medical device from a first value to a second value.

[0008] In another example, this disclosure describes non-transitory computer-readable storage medium storing instructions, which when executed, cause processing circuitry to: receive an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; receive at least one of an identified intrinsic event of a second chamber of the heart of the patient sensed via a secondlead implanted in the second chamber or an identified paced event of the second chamber sensed via the second lead; generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and in response to determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of an implantable medical device from a first value to a second value.

[0009] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the methods and systems described in detail within the accompanying drawings and description below. The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below.BRIEF DESCRIPTION OF DRAWINGS

[0010] The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

[0011] FIG. 1 is conceptual diagram illustrating an example medical device system, in accordance with some examples of the current disclosure.

[0012] FIG. 2 is a conceptual diagram further illustrating the implantable medical device (IMD) of FIG. 1, in accordance with some examples of the current disclosure.

[0013] FIG. 3 is a functional block diagram illustrating an example configuration of implantable medical device of FIGS. 1 and 2, in accordance with some examples of the current disclosure.

[0014] FIG. 4 is a functional block diagram illustrating an example configuration of the external device of the medical system of FIG. 1, in accordance with some examples of the current disclosure.

[0015] FIG. 5 is a block diagram illustrating an example system that includes an external device, such as a server, and one or more computing devices that are coupled to theIMD and external device shown in FIG. 1 via a network, in accordance with some examples of the current disclosure.

[0016] FIG. 6 is a flow diagram illustrating an example technique for adjusting a sensitivity threshold, in accordance with some examples of the current disclosure.

[0017] FIG. 7 is a flow diagram illustrating an example technique for adjusting a sensitivity threshold, in accordance with some examples of the current disclosure.

[0018] Like reference characters denote like elements throughout the description and figures.DETAILED DESCRIPTION

[0019] An implantable medical system includes an implantable medical device (IMD), such as a pacemaker, implantable cardioverter defibrillator (ICD), or implantable cardiac resynchronization therapy (CRT), that may provide therapies for maintaining and restoring normal cardiac rhythms by pacing and / or by delivering electrical shock therapy for cardioverting or defibrillating the heart. One or more electrical leads connected to the IMD may be inserted into or in proximity to the heart of the patient. The leads carry therapeutic current from the IMD to the heart tissue to either stimulate the heart using low energy pacing pulses or cardio vert / defibrillate the heart using relatively higher energy shocks. The IMD also uses the leads for sensing electrical activity, such as electrogram (EGM) signals, from the heart. Using the EGM signals, the IMD may detect cardiac depolarizations, repolarizations, or other activity, and detect arrhythmias responsive to which the IMD may deliver the electrical therapy. In some examples, within the IMD, sense amplifiers may amplify EGM signals from electrodes on the leads, and the amplified EGM signals may be used by the IMD to sense intrinsic depolarizations of the atria (referred to as P-waves) and the ventricles (referred to as R-waves).

[0020] The implantable medical systems may also include one or more leads that are wholly or partially implanted within the patient and are configured to couple to the IMDs. In some examples, the implantable leads include an integrated bipolar lead, in which an electrode used to deliver relatively higher energy shock therapy, e.g., a coil electrode, serves as either an anode or cathode of a sensing vector, such as a sensing bipole. The sensing bipole of an integrated bipolar lead may have larger (e.g., wider) spacing than a traditional bipolar lead that includes, for example, two relatively more closely spaced electrodes, suchas a tip electrode and a ring electrode or two closely spaced ring electrodes. Because of the larger interelectrode spacing, the integrated bipolar lead may capture more of far-field signals. In some examples, an integrated bipolar lead may include a defibrillator coil electrode connected to a ring electrode with the combination of the defibrillator coil electrode and the ring electrode acting as an anode or cathode of a sensing bipole of the integrated bipolar lead.

[0021] Integrated bipolar leads that are implanted ventricularly consequently may have a higher chance of atrial oversensing, particularly for integrated bipolar leads that are implanted in the left bundle branch area, septal area, or other higher up / closer to the atrium than conventional apical implantation. In some examples, a position of an integrated bipolar lead may be adjusted, such as by an implanter, at implant to reduce the chance of a ventricularly-implanted integrated bipolar lead oversensing atrial far-field activity.However, in some cases over time, the ventricularly-implanted integrated bipolar lead may sense atrial far-field activity which may lead to atrial oversensing. For example, after the leads are implanted, a position of the leads may change, such as due to patient movement, which may cause an increase in sensed atrial far-field activity by an integrated bipolar lead implanted in a ventricle, which can lead to atrial oversensing. Atrial oversensing may lead to a variety of undesired outcomes, such as over-detection of tachyarrhythmias, inhibition of cardiac resynchronization therapy (CRT) and / or loss of optimal AV interval for CRT or other synchronous ventricular pacing.

[0022] In general, this disclosure describes example techniques related to adjusting a sensitivity threshold to prevent or reduce a likelihood of oversensing far-field activity via an integrated bipolar lead in a multi-chamber system, such as a ventricularly-implanted integrated bipolar lead. For example, an IMD, may monitor one or more features of EGM signals sensed by an atrial lead and a ventricular integrated bipolar lead, such as during normal 1: 1 rhythm. In some examples, the IMD may periodically determine one or more features of one or more EGM signals sensed by a ventricular integrated bipolar lead. In some examples, the IMD may periodically determine an amplitude or other metric of a windowed portion of the EGM signals sensed by a ventricular integrated bipolar lead.

[0023] In some examples, the IMD may, via an atrial lead, sense an atrial intrinsic event of a patient and / or perform an atrial paced event on the patient. The IMD may periodically perform windowing to generate a time window of the EGM signal sensed by the ventricularintegrated bipolar lead based on one or more of the atrial intrinsic event or the atrial paced event. For example, the IMD may generate a time window of the EGM signal sensed via the integrated bipolar lead from a pre-atrial event time, such as up to 50 milliseconds (ms) before the atrial intrinsic event, between 20-70 ms before the atrial intrinsic event, or 50 ms before the atrial intrinsic event, to a post-atrial event time, such as up to 120 ms after the intrinsic atrial event, between 100-140 ms after the intrinsic atrial event, or 120 ms after the intrinsic atrial event. In some examples, the IMD may generate a time window of the EGM signal sensed by the integrated bipolar from at or near an atrial paced event position to a post-atrial paced event position, such as up to 170 ms after the atrial paced event , between 150-190 ms after the atrial paced event , or 170 ms after the atrial paced event.

[0024] The IMD may periodically determine a value of one or more features of the EGM signal during the generated time window, such as a P-wave amplitude, peak-to-peak amplitude, maximum peak amplitude, minimum trough amplitude, slew rate, or other features. In some examples, the IMD may compare the values of the one or more features of the EGM signal to a baseline value of a respective feature of the EGM signal. In some examples, a baseline value for one or more features of the EGM signal may generated shortly after the ventricular integrated bipolar lead and atrial lead are implanted in a patient. In some examples, a baseline value for one or more features of the EGM signal may be predetermined. The baseline values for features of the EGM signal may be configured to represent measurements of those respective features when the ventricular integrated bipolar lead senses a minimal amount of atrial far-field activity.

[0025] In some examples, when a change in value of the one or more features of the EGM signal within the window, such as an amplitude, with respect to a baseline value of a respective feature of the EGM signal satisfies a change threshold and / or the value of the one or more features of the EGM signal within the window satisfies a far-field activity threshold, the IMD may periodically adjust the sensitivity threshold applied to signals sensed via the ventricularly-implanted integrated bipolar lead. For example, the IMD may increase the sensitivity threshold to reduce a likelihood of subsequent instances of atrial oversensing, i.e., of misidentifying P-wave activity in the ventricular EGM signal as an R- wave. In some examples, the IMD may increase a sensitivity threshold by between 10% to 50% of the current sensitivity threshold to reduce subsequent instances of atrial oversensing, such as P-wave oversensing. In some examples, periodically may be every hour, every 4hours, every 6 hours, every 8 hours, every 12 hours, every 24 hours, or every 48 hours. In other examples, periodically may be other periods of time not listed above.

[0026] FIG. 1 illustrates example medical device system 10 in conjunction with patient 14. Medical device system 10 is an example of a medical device system that is configured to implement the example techniques described herein for adjusting a sensitivity threshold to reduce a likelihood of far-field oversensing via an integrated bipolar lead. In some examples, medical device system 10 includes an implantable medical device (IMD) 16 in communication with external device 24. In the illustrated example, IMD 16 may be coupled to leads 18, 20, and 22. IMD 16 may be, for example, an implantable pacemaker that provides electrical signals to heart 12 and senses electrical activity of heart 12 via electrodes coupled to one or more of leads 18, 20, and 22. In some examples, IMD 16 may include cardioversion and / or defibrillation capabilities.

[0027] Leads 18, 20, 22 extend into heart 12 of patient 14 to sense electrical activity of heart 12 and to deliver electrical therapy to heart 12. In the example shown in FIG. 1, right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium (RA) 26, and into RV 28. Left ventricular (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of LV 32 of heart 12. Right atrial (RA) lead 22 extends through one or more veins and the vena cava, and into the RA 26 of heart 12.

[0028] In some examples, lead 18 may be referred to as a ventricularly-implanted integrated bipolar lead. In some examples, lead 22 may be referred to as an atrial lead. Although an apical implantation location of lead 18 is illustrated in FIG. 1, ventricularly- implanted integrated bipolar lead 18 may be implanted in other locations in some examples, such as proximate the left bundle branch, ventricular septum, or more generally closer to the right atrium.

[0029] IMD 16 may sense electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes (not shown in FIG. 1) coupled to at least one of the leads 18, 20, 22. In some examples, IMD 16 may also sense electrical signals attendant to the depolarization and repolarization of heart 12 via extravascular electrodes (e.g., electrodes positioned outside the vasculature of patient 14), such as epicardial electrodes,external surface electrodes, subcutaneous electrodes, and the like. The configurations of electrodes used by IMD 16 for sensing and pacing may be unipolar or bipolar.

[0030] The natural electrical activation system of a human heart 12 involves several sequential conduction pathways starting with the sino-atrial (SA) node, and continuing through the atrial conduction pathways of Bachmann's bundle and intemodal tracts at the atrial level, followed by the atrio- ventricular (AV) node, Common Bundle of His, right and left bundle branches, and a final distribution to the distal myocardial terminals via the Purkinje fiber network. In a normal electrical activation sequence, the cardiac cycle commences with the generation of a depolarization wave at the SA Node in the wall of RA 26. The depolarization wave is transmitted through the atrial conduction pathways of Bachmann's Bundle and the Intemodal Tracts at the atrial level into the LA 33 septum. When the atrial depolarization wave has reached the AV node, the atrial septum, and the furthest walls of the right and left atria 26, 33, respectively, the atria 26, 33 may contract as a result of the electrical activation. The aggregate right atrial and left atrial depolarization wave appears as the P-wave of the PQRST complex of a cardiac EGM. When the amplitude of the atrial depolarization wave passing between a pair of unipolar or bipolar pace / sense electrodes located on or adjacent RA 26 and / or LA 33 exceeds a threshold, it is detected as a sensed P-wave. The sensed P-wave may also be referred to as an atrial intrinsic event.

[0031] During or after the atrial contractions, the AV node distributes the depolarization wave inferiorly down the Bundle of His in the intraventricular septum. The depolarization wave may travel to the apical region of heart 12 and then superiorly though the Purkinje Fiber network. The aggregate right ventricular and left ventricular depolarization wave and the subsequent T-wave accompanying re -polarization of the depolarized myocardium may appear as the QRST portion of the PQRST cardiac cycle complex. When the amplitude of the QRS ventricular depolarization wave passing between a bipolar or unipolar pace / sense electrode pair located on or adjacent RV 28 and / or LV 32 exceeds a threshold, it is detected as a sensed R-wave. The sensed R-wave may also be referred to as a ventricular intrinsic event, an RV sensing event (RVs), or an LV sensing event (LVs) depending upon the ventricle in which the electrodes of one or more of leads 18, 20, 22 are configured to sense in a particular case.

[0032] In some examples, IMD 16 provides defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 22. Based on signals sensed via one or more of leads 18, 20, 22, e.g., the detection of R-waves, IMD 16 may detect arrhythmia of heart 12, such as fibrillation or other tachyarrhythmia of ventricles 28 and 32, and deliver antitachyarrhythmia therapy to heart 12 in the form of electrical shocks. In some examples, IMD 16 is programmed to deliver a progression of therapies, e.g., shocks with increasing energy levels, until a tachyarrhythmia of heart 12 is stopped. In examples in which IMD 16 provides antitachyarrhythmia shock therapy, IMD 16 may detect tachyarrhythmia by employing any one or more tachyarrhythmia detection techniques known in the art.

[0033] In some examples, external device 24 may be a handheld computing device or a computer workstation. External device 24 may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions. External device 24 can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some examples, a display of external device 24 may include a touch screen display, and a user may interact with external device 24 via the display.

[0034] A user, such as a physician, technician, or other clinician, may interact with external device 24 to communicate with IMD 16. For example, the user may interact with external device 24 to retrieve physiological or diagnostic information from IMD 16. A user may also interact with external device 24 to program IMD 16, e.g., to select values for operational parameters of the IMD 16.

[0035] For example, the user may use external device 24 to retrieve information from IMD 16 regarding the rhythm of heart 12, trends therein over time, or arrhythmia episodes. As another example, the user may use external device 24 to retrieve information from IMD 16 regarding other sensed physiological parameters of patient 14, such as sensed electrical activity, activity, posture, respiration, or thoracic impedance. As another example, the user may use external device 24 to retrieve information from IMD 16 regarding the performance or integrity of IMD 16 or other components of system 10, such as leads 18, 20, and 22, or a power source of IMD 16. In such examples, physiological parameters of patient 14 and dataregarding IMD 16 may be stored in a memory of IMD 16 for retrieval by the user. The user may use external device 24 to program parameters of therapy delivery by IMD 16 and / or parameters used for depolarization and / or arrhythmia detection by IMD 16. In some examples, the user may activate certain features of IMD 16 by entering a single command via external device 24, such as depression of a single key or combination of keys of a keypad or a single point- and- select action with a pointing device.

[0036] IMD 16 and external device 24 may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, include radiofrequency (RF) telemetry, which may be an RF link established via an antenna according to Bluetooth®, WiFi, or medical implant communication service (MICS), though other techniques are also contemplated. In some examples, external device 24 may include a programming head that may be placed proximate to the patient’s body near the IMD 16 implant site in order to improve the quality or security of communication between IMD 16 and external device 24.

[0037] FIG. 2 is a conceptual diagram further illustrating an example configuration of IMD 16 in conjunction with heart 14. In the example of FIG. 2, IMD 16 is coupled to leads 18 and 22. IMD 16 may be coupled to two leads as illustrated in FIG. 2, three leads as illustrated in FIG. 1, or other numbers of leads. Furthermore, the leads coupled to IMD 16 may be configured differently than those illustrated herein, but IMD 16 may nevertheless implement the techniques of this disclosure.

[0038] As shown in FIG. 2, the proximal ends of leads 18 and 22 are connected to a connector block 34 of IMD 16 to electrically couple the electrodes on the leads to circuitry within the housing 60 of IMD 16. In some examples, proximal ends of leads 18 and 22 may include electrical contacts that electrically couple to respective electrical contacts within connector block 34 of IMD 16. Each of the leads 18 and 22 includes an elongated insulative lead body, which may carry a number of conductors, e.g., a conductor for each electrode on the lead, each of which may be connected to a respective contact at the proximal end of the lead. Bipolar electrode 42 is located adjacent to a distal end of lead 18 in right ventricle 28. In addition, bipolar electrodes 48 and 50 are located adjacent to a distal end of lead 22 in right atrium 26.

[0039] In some examples, lead 18 may be referred to as a ventricularly-implanted integrated bipolar lead 18 or a ventricular integrated bipolar lead 18. As will be described ingreater detail below, lead 18 may be configured to facilitate sensing of a ventricular EGM by IMD 16 via an integrated bipolar pair including tip electrode 42 and elongated electrode 62. In some examples, lead 22 may be referred to as an atrial lead 22.

[0040] Electrode 48 may take the form of ring electrodes, and electrodes 42 and 50 may take the form of helix tip electrodes mounted, e.g., with a fixed screw, within insulative electrode heads 52 and 56, respectively. Some helix tip electrodes can include a mechanism for an extendable / retractable helix. In other examples, one or more of electrodes 42 and 50 may take the form of small circular electrodes at the tip of a tined lead or other fixation element. Leads 18 and 22 also include elongated electrodes 62 and 66, respectively, each of which may take the form of a coil, and may be configured for delivery of relatively high energy therapeutic shocks. Each of the electrodes 42, 48, 50, 62 and 66 may be electrically coupled to a respective one of the conductors within the lead body of its associated lead 18 and 22, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads 18 and 22.

[0041] In the example of FIG. 2, IMD 16 includes a housing electrode 58, which may be formed integrally with an outer surface of hermetically- sealed housing 60 of IMD 16, or otherwise coupled to housing 60. In some examples, housing electrode 58 is defined by an uninsulated portion of an outward facing portion of housing 60 of IMD 16. Other division between insulated and uninsulated portions of housing 60 may be employed to define two or more housing electrodes. In some examples, housing electrode 58 comprises substantially all of housing 60.

[0042] IMD 16 may sense electrical signals attendant to the depolarization and repolarization of heart 12 via electrodes 42, 48, 50, 62, and 66. The electrical signals are conducted to IMD 16 from the electrodes via the respective leads 18 and 22. IMD 16 may sense such electrical signals via any bipolar combination of electrodes 40, 42, 48, 50, 62, and 66. For example, IMD 16 may sense a ventricular EGM via an integrated bipolar pair including tip electrode 42 and elongated electrode 62. Furthermore, any of the electrodes 42, 48, 50, 62, and 66 may be used for unipolar sensing in combination with housing electrode 58. The combination of electrodes used for sensing may be referred to as a sensing configuration or electrode vector.

[0043] In some examples, IMD 16 delivers pacing pulses via bipolar combinations of electrodes 42, 48, 50, 62, and 66 to produce depolarization of cardiac tissue of heart 12. Insome examples, IMD 16 delivers pacing pulses via any of electrodes 42, 48 and 50 in combination with housing electrode 58 in a unipolar configuration. Furthermore, IMD 16 may deliver antitachyarrhythmia shocks, e.g., defibrillation shocks, to heart 12 via any combination of elongated electrodes 62 and 66, and housing electrode 58. IMD 16 may also use electrodes 58, 62, and 66 to deliver cardioversion shocks to heart 12. Electrodes 62 and 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

[0044] The configurations of system 10 illustrated in FIGS. 1 and 2 are merely examples. In other examples, a system may include extravascular leads and electrodes instead of or in addition to the illustrated transvenous leads 18 and 22. Further, IMD 16 need not be implanted within the patient. In examples in which IMD 16 is not implanted in the patient, IMD 16 may sense electrical signals and / or deliver antitachyarrhythmia shocks and other therapies to heart 12 via percutaneous leads that extend through the skin of a patient to a variety of positions within or outside of heart 12.

[0045] Some additional or alternative examples of IMD 16 are described in U.S. Patent No. 7,236,828 to Casavant et al., entitled, “IMPLANT ABLE CARDIOVERTER DEFRIBILLATOR WITH AUTOMATICALLY SENSING CONFIGURATION,” which issued on June 26, 2007, U.S. Patent No. 7,953,488 to Casavant et al., entitled, “PREQUALIFICATION OF AN ALTERNATE SENSING CONFIGURATION,” which issued on May 31, 2011, and / or in U.S. Publication No. 2021 / 0402197 to Zhang et al., entitled, “SYSTEM AND METHOD FOR IDENTIFYING AND RESPONDING TO P-WAVE OVERSENSING IN A CARDIAC SYSTEM,” which published on December 30, 2021, each of which are incorporated herein by reference in their entireties.

[0046] FIG. 3 is a functional block diagram of one example configuration of IMD 16 of FIGS. 1 and 2. In the illustrated example, IMD 16 includes memory 70, processing circuitry 80, sensing circuitry 82, one or more accelerometers 84, therapy delivery circuitry 86, telemetry circuitry 88, and power source 90, one or more of which may be disposed within housing 60 of IMD 16. In some examples, memory 70 includes computer-readable instructions that, when executed by processing circuitry 80, cause IMD 16 and processing circuitry 80 to perform various functions attributed to IMD 16 and processing circuitry 80 herein. Memory 70 may include any volatile, non-volatile, magnetic, optical, or electricalmedia, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media. Sensed physiological parameters of patient 14 (e.g., EGM or ECG signals or atrial events) may be stored by memory 70.

[0047] Processing circuitry 80 may include one or more of a microprocessor, a controller, digital signal processing circuitry (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some examples, processing circuitry 80 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry 80 herein may be embodied as software, firmware, hardware or any combination thereof. According to the techniques described herein, processing circuitry 80 may be configured to generate a time window of the integrated bipolar EGM signal based on one or more of an atrial intrinsic event or an atrial paced event, determine a value of one or more features of the EGM signal during the time window, determine the value of the one or more features of the EGM signal satisfies a far-field activity threshold, and in response to determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a value of a sensitivity threshold used by processing circuitry 80 and / or sensing circuitry 82 to sense depolarization of the intended chamber, e.g., R-waves, in the integrated bipolar EGM, e.g., adjusting the sensitivity threshold from a first value to a second value. The second value may be higher than the first value, which may make the threshold less sensitive to depolarizations.

[0048] Sensing circuitry 82 is configured to monitor signals from at least one of electrodes 42, 48, 50, 58, 62, or 66 in order to monitor electrical activity of heart 12, e.g., via EGM signals. For example, sensing circuitry 82 may sense atrial intrinsic events (e.g., a P-wave) with electrodes 48, 50, 66 within RA 26. In some examples, sensing circuitry 82 includes switching circuitry to select which of the available electrodes are used to sense the electrical activity of heart 12. For example, processing circuitry 80 may select the electrodes that function as sense electrodes via the switching circuitry within sensing circuitry 82, e.g., by providing signals via a data / address bus. In some examples, sensing circuitry 82 includes one or more sensing channels, each of which may comprise anamplifier. In response to the signals from processing circuitry 80, the switching circuitry of sensing circuitry 82 may couple the outputs from the selected electrodes to one of the sensing channels.

[0049] In some examples, one channel of sensing circuitry 82 may include an R-wave amplifier that receives signals from selected pairs of electrodes 42, 62, and 60, which are used for pacing and sensing in RV 28 of heart 12. In accordance with the techniques of this disclosure, sensing circuitry 82 may include an R-wave amplifier that receives a signal from an integrated bipolar pair of electrodes 42 and 62, i.e., an integrated bipolar ventricular EGM signal, and detects R-waves within the signal. In some examples, the R-wave amplifiers may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm. In accordance with the techniques of this disclosure, processing circuitry 80 may adjust a parameter of the adjustable sensing threshold, e.g., to increase the threshold and make the threshold less sensitive to waves in the integrated bipolar ventricular EGM signal, in response to a windowed portion of the integrated bipolar ventricular EGM signal satisfying a far-field activity threshold.

[0050] In addition, in some examples, one channel of sensing circuitry 82 may include a P-wave amplifier that receives signals from electrodes 48 and 50, which are used for pacing and sensing in RA 26 of heart 12. In some examples, the P-wave amplifier may take the form of an automatic gain controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in U.S. Patent No. 5,117,824 to Keimel et al., which issued on June 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in its entirety. Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of sensing circuitry 82 may be selectively coupled to housing electrode 58, or elongated electrodes 62, or 66, with or instead of one or more of electrodes 42, 48 or 50, e.g., for unipolar or integrated bipolar sensing of R-waves or P- waves in any of chambers 26, 28, or 32 of heart 12.

[0051] In some examples, sensing circuitry 82 includes a channel that comprises an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers. Signals from the selected sensing electrodes that are selected for coupling to this wide-bandamplifier may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in memory 70 as an EGM. In some examples, the storage of such EGMs in memory 70 may be under the control of a direct memory access circuit. Processing circuitry 80 may employ digital signal analysis techniques to characterize the digitized signals stored in memory 70 to detect and classify the patient's heart rhythm from the electrical signals. Processing circuitry 80 may detect and classify the heart rhythm of patient 14 by employing any of the numerous signal processing methodologies known in the art. In some examples, sensing 82 stores the integrated bipolar EGM, e.g., the ventricular integrated bipolar EGM, in memory 70 for windowing and further processing by processing circuitry 80 in accordance with the techniques of this disclosure.

[0052] Signals generated by sensing circuitry 82 may include, for example: an RA- event signal, which indicates a detection of a P-wave via electrodes implanted within RA 26 (FIG. 1); an LA-event signal, which indicates a detection of a P-wave via electrodes implanted within LA 33 (FIG. 1); an RV-event signal, which indicates a detection of an R- wave via electrodes implanted within RV 28; or an LV-event signal, which indicates a detection of an R-wave via electrodes implanted within LV 32.

[0053] In some examples, IMD 16 may include one or more additional sensors, such as accelerometers 84. In some examples, accelerometers 84 may comprise one or more three- axis accelerometers. Signals generated by accelerometers 84 may be indicative of, for example, gross body movement of patient 14, such as a patient posture or activity level. Regardless of the configuration of accelerometers 84, processing circuitry 80 may determine patient parameter values based on the signals obtained therefrom. Accelerometers 84 may produce and provide signals to processing circuitry 80 for a determination as to the posture and activity level of patient 14 at a given time. Processing circuitry 80 may then use the determined posture and activity level to further determine whether patient 14 is awake or asleep, and, if patient 14 is determined to be awake, to further determine whether patient 14 is at rest or exercising.

[0054] Therapy delivery circuitry 86 is electrically coupled to electrodes 42, 48, 50, 58, 62, and 66, e.g., via conductors of the respective lead 18, 20, 22, or, in the case of housing electrode 58, via an electrical conductor disposed within housing 60 of IMD 16. Therapy delivery circuitry 86 is configured to generate and deliver electrical therapy.

[0055] In some examples, therapy delivery circuitry 86 is configured to deliver cardioversion or defibrillation shocks to heart 12. The pacing stimuli, cardioversion shocks, and defibrillation shocks may be in the form of pulses. In other examples, therapy delivery circuitry 86 may deliver one or more of these types of therapy in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

[0056] Therapy delivery circuitry 86 may include a switching circuitry, and processing circuitry 80 may use the switching circuitry to select, e.g., via a data / address bus, which of the available electrodes are used to deliver shock pulses or pacing pulses. The switching circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple therapeutic energy to selected electrodes. In other examples, processing circuitry 80 may select a subset of electrodes 42, 48, 50, 58, 62, and 66 with which therapy is delivered to heart 12 without a switching circuitry.

[0057] Processing circuitry 80 may include pacer timing and control circuitry, which may be embodied as hardware, firmware, software, or any combination thereof. Pacer timing and control circuitry may comprise a dedicated hardware circuit, such as an ASIC, separate from other processing circuitry 80 components, such as a microprocessor, or a software module executed by a component of processing circuitry 80 (e.g., a microprocessor or ASIC).

[0058] In some examples, an arrhythmia detection method may include any suitable tachyarrhythmia detection algorithms. In one example, processing circuitry 80 may utilize all or a subset of the rule-based detection methods described in U.S. Patent No. 5,545,182 to Olson et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on August 13, 1996, or in U.S. Patent No. 5,755,736 to Gillberg et al., entitled, “PRIORITIZED RULE BASED METHOD AND APPARATUS FOR DIAGNOSIS AND TREATMENT OF ARRHYTHMIAS,” which issued on May 26, 1998. U.S. Patent No. 5,545,182 to Olson et al. and U.S. Patent No. 5,755,736 to Gillberg et al. are incorporated herein by reference in their entireties. However, other arrhythmia detection methodologies may also be employed by processing circuitry 80 in other examples.

[0059] If IMD 16 is configured to generate and deliver defibrillation shocks to heart 12, therapy delivery circuitry 86 may include a high voltage charge circuit and a high voltage output circuit. In the event that processing circuitry 80 determines that generation of acardioversion or defibrillation shock is required, processing circuitry 80 may employ the escape interval counter to control timing of such cardioversion and defibrillation shocks, as well as associated refractory periods. In response to the detection of atrial or ventricular fibrillation or tachyarrhythmia requiring a cardioversion pulse, processing circuitry 80 may activate a cardioversion / defibrillation control circuitry (not shown), which may be a hardware component of processing circuitry 80 and / or a firmware or software module executed by one or more hardware components of processing circuitry 80. The cardioversion / defibrillation control circuitry may initiate charging of the high voltage capacitors of the high voltage charge circuit of therapy delivery circuitry 86 under control of a high voltage charging control line.

[0060] Processing circuitry 80 may monitor the voltage on the high voltage capacitor, e.g., via a voltage charging and potential (VCAP) line. In response to the voltage on the high voltage capacitor reaching a predetermined value set by processing circuitry 80, processing circuitry 80 may generate a logic signal that terminates charging. Thereafter, timing of the delivery of the defibrillation or cardioversion pulse by therapy delivery circuitry 86 is controlled by a cardioversion / defibrillation control circuitry (not shown) of processing circuitry 80. Following delivery of the fibrillation or tachycardia therapy, processing circuitry 80 may return therapy delivery circuitry 86 to a cardiac pacing function and await the next successive interrupt due to pacing or the occurrence of a sensed atrial or ventricular depolarization.

[0061] Therapy delivery circuitry 86 may deliver cardioversion or defibrillation shock with the aid of an output circuit that determines whether a monophasic or biphasic pulse is delivered, whether housing electrode 58 serves as cathode or anode, and which electrodes are involved in delivery of the cardioversion or defibrillation pulses. Such functionality may be provided by one or more switches or a switching circuitry of therapy delivery circuitry 86.

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

[0063] In some examples, processing circuitry 80 may transmit atrial and ventricular heart signals (e.g., EGM signals) produced by atrial and ventricular sense amplifier circuits within sensing circuitry 82 to external device 24. Other types of information may also be transmitted to external device 24, such as indications of satisfaction of the far-field activity threshold and / or adjustment of the sensitivity threshold. External device 24 may interrogate IMD 16 to receive the heart signals. Processing circuitry 80 may store heart signals within memory 70, and retrieve stored heart signals from memory 70. Processing circuitry 80 may also generate and store marker codes indicative of different cardiac episodes that sensing circuitry 82 detects, and transmit the marker codes to external device 24. An example pacemaker with marker-channel capability is described in U.S. Patent No. 4,374,382 to Markowitz, entitled, “MARKER CHANNEL TELEMETRY SYSTEM FOR A MEDICAL DEVICE,” which issued on February 15, 1983 and is incorporated herein by reference in its entirety.

[0064] Telemetry circuitry 88 includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device 24 (FIG. 1). Under the control of processing circuitry 80, telemetry circuitry 88 may receive downlink telemetry from and send uplink telemetry to external device 24 with the aid of an antenna, which may be internal and / or external. Processing circuitry 80 may provide the data to be uplinked to external device 24 and the control signals for the telemetry circuit within telemetry circuitry 88, e.g., via an address / data bus. In some examples, telemetry circuitry 88 may provide received data to processing circuitry 80 via a multiplexer.

[0065] The various components of IMD 16 are coupled to power source 90, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

[0066] FIG. 4 is functional block diagram of an example external device 24. As shown in FIG. 4, external device 24 includes processing circuitry 100, a memory 102, a user interface 104, telemetry circuitry 106, and a power source 108. External device 24 may be a dedicated hardware device with dedicated software for interacting with IMD 16.Alternatively, external device 24 may be an off-the-shelf computing device running an application that enables external device 24 to interact with IMD 16.

[0067] A user may use external device 24 to select programmable parameters that control the monitoring and delivery of therapy by IMD 16, and to retrieve information collected by IMD regarding the condition of patient 14 or the performance of IMD 16. The user may interact with external device 24 via user interface 104, which may include display to present graphical user interface to a user, and a keypad or another mechanism for receiving input from a user.

[0068] Processing circuitry 100 can take the form one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, and the functions attributed to processing circuitry 102 herein may be embodied as hardware, firmware, software or any combination thereof. Memory 102 may store instructions that cause processing circuitry 100 to provide the functionality ascribed to external device 24 herein, and information used by processing circuitry 100 to provide the functionality ascribed to external device 24 herein. Memory 102 may include any fixed or removable magnetic, optical, or electrical media, such as RAM, ROM, CD-ROM, hard or floppy magnetic disks, EEPROM, or the like. Memory 102 may also include a removable memory portion that may be used to provide memory updates or increases in memory capacities. A removable memory may also allow patient data to be easily transferred to another computing device, or to be removed before external device 24 is used to program therapy for another patient. Memory 102 may also store information that controls therapy delivery by IMD 16, such as stimulation parameter values.

[0069] External device 24 may communicate wirelessly with IMD 16, such as using RF communication or proximal inductive interaction. This wireless communication is possible through the use of telemetry circuitry 106, which may be coupled to an internal antenna or an external antenna. An external antenna that is coupled to external device 24 may correspond to the programming head that may be placed over heart 12, as described above with reference to FIG. 1.

[0070] Telemetry circuitry 106 may be similar to telemetry circuitry 88 of IMD 16 (FIG. 3). Telemetry circuitry 106 may also be configured to communicate with another computing device via wireless communication techniques, or direct communication through a wired connection. Examples of local wireless communication techniques that may beemployed to facilitate communication between external device 24 and another computing device include RF communication according to the 802.11 or Bluetooth specification sets, infrared communication, e.g., according to the IrDA standard, or other standard or proprietary telemetry protocols. In this manner, other external devices may be capable of communicating with external device 24 without needing to establish a secure wireless connection.

[0071] Power source 108 is configured to deliver operating power to the components of external device 24. Power source 108 may include a battery and a power generation circuit to produce the operating power. In some embodiments, the battery may be rechargeable to allow extended operation. Recharging may be accomplished by electrically coupling power source 108 to a cradle or plug that is connected to an alternating current (AC) outlet. In addition or alternatively, recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within external device 24. In other embodiments, traditional batteries (e.g., nickel cadmium or lithium ion batteries) may be used. In addition, external device 24 may be directly coupled to an alternating current outlet to power external device 24. Power source 108 may include circuitry to monitor power remaining within a battery. In this manner, user interface 104 may provide a current battery level indicator or low battery level indicator when the battery needs to be replaced or recharged. In some cases, power source 108 may be capable of estimating the remaining time of operation using the current battery.

[0072] In some examples, processing circuitry 100 and memory 102 of external device 24 may be configured to provide some or all of the functionality ascribed to processing circuitry 80 and memory 70 of IMD 16. In some examples, processing circuitry 100 may be configured to generate a time window of an integrated bipolar EGM signal, determine values of one or more features of the EGM signal during the time window, and adjust a sensitivity threshold used by IMD 16 to detect near field depolarizations, as described herein with respect to processing circuitry 80 of IMD 16.

[0073] FIG. 5 is a block diagram illustrating a system 110 that includes an external device 112, such as a server, and one or more computing devices 114A-114N that are coupled to IMD 16 and external device 24 shown in FIG. 1 via a network 120, according to one example. In this example, IMD 16 uses telemetry circuitry 88 (FIG. 3) to communicate with external device 24 via a first wireless connection, and to communicate with an accesspoint 122 via a second wireless connection. In the example of FIG. 5, access point 122, external device 24, external device 112, and computing devices 114A-114N are interconnected, and able to communicate with each other, through network 120. In some cases, one or more of access point 122, external device 24, external device 112, and computing devices 114A-114N may be coupled to network 120 through one or more wireless connections. IMD 16, external device 24, external device 112, and computing devices 114A-114N may each comprise one or more processing circuitries, such as one or more microprocessors, DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, that may perform various functions and operations, such as those described herein.

[0074] Access point 122 may comprise a device that connects to network 120 via any of a variety of connections, such as telephone dial-up, digital subscriber line (DSL), or cable modem connections. In other examples, access point 122 may be coupled to network 120 through different forms of connections, including wired or wireless connections. In some examples, access point 122 may communicate with external device 24 and / or IMD 16. Access point 122 may be co-located with patient 14 (e.g., within the same room or within the same site as patient 14) or may be remotely located from patient 14. For example, access point 122 may be a home monitor that is located in the patient’s home or is portable for carrying with patient 14.

[0075] During operation, IMD 16 may collect, measure, and store various forms of diagnostic data. For example, as described previously, IMD 16 may collect EGM signals, generate a time window of an integrated bipolar EGM signal, determine values of one or more features of the integrated bipolar EGM signal during the time window, and adjust a sensitivity threshold used to detect R-waves or other near field depolarizations. In certain cases, IMD 16 may directly analyze collected diagnostic data and generate any corresponding reports or alerts. In some cases, however, IMD 16 may send diagnostic data to external device 24, access point 122, and / or external device 112, either wirelessly or via access point 122 and network 110, for remote processing and analysis.

[0076] For example, IMD 16 may send external device 24 a system integrity indication generated by processing circuitry 80 (FIG. 3) to external device 24, which may take further steps to determine whether there may be a possible condition with one or more of leads 18, 20, and 22. For example, external device 24 may initiate lead impedance tests or IMD 16 may provide lead impedance information, if such information is already available. Inanother example, IMD 16 may provide external device 112 with collected EGM data, system integrity indications, and any other relevant physiological or system data via access point 122 and network 120. External device 112 includes one or more processing circuitries 118. In some cases, external device 112 may request such data, and in some cases, IMD 16 may automatically or periodically provide such data to external device 112. Upon receipt of the diagnostic data via input / output device 116, external device 112 is capable of analyzing the data and generating reports or alerts upon determination that there may be a possible condition with one or more of leads 18, 20, and 22 or with patient 14.

[0077] In one example, external device 112 may comprise a secure storage site for information that has been collected from IMD 16 and / or external device 24. In this example, network 120 may comprise an Internet network; and trained professionals, such as clinicians, may use computing devices 114A-114N to securely access stored data on external device 112. For example, the trained professionals may need to enter usernames and passwords to access the stored information on external device 112. In one embodiment, external device 112 may be a CareLink server provided by Medtronic, Inc., of Minneapolis, Minnesota.

[0078] In some examples, processing circuitry and memory of one or more of access point 122, server 112, or computing devices 114, e.g., processing circuitry 118 and memory of server 112, may be configured to provide some or all of the functionality ascribed to processing circuitry 80 and memory 70 of IMD 16. In some examples, processing circuitry 118 may be configured to generate a time window of the integrated bipolar EGM signal based on one or more of an atrial intrinsic event or an atrial paced event, determine a value of one or more features of the EGM signal during the time window, determine the value of the one or more features of the EGM signal satisfies a far-field activity threshold, and in response to determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a value of a sensitivity threshold used by processing circuitry 118 to sense depolarization of the intended chamber, e.g., R-waves, in the integrated bipolar EGM, e.g., adjusting the sensitivity threshold from a first value to a second value. The second value may be higher than the first value, which may make the threshold less sensitive to depolarizations.

[0079] FIGS. 6-7 are flow diagrams illustrating various techniques related to adjusting a sensitivity threshold, such as a ventricular sensitivity threshold, in accordance withexamples of this disclosure. As described herein, the techniques illustrated FIGS. 6-7 may be employed using one or more components of system 10, which have been described above with respect to FIGS. 1-5. Although described as being performed by processing circuitry 80 of IMD 16, the techniques of FIGS. 6-7 may be performed, in whole or in part, by processing circuitry and memory of other devices of a medical device system, as described herein.

[0080] FIG. 6 is a flow diagram illustrating an example technique for operation of a medical system 10 to adjust a sensitivity threshold for detection near field depolarizations in an EGM signal sensed by an integrated bipolar lead. The example of FIG. 6 is detection of R-waves via a ventricular integrated bipolar lead, although the example operation of FIG. may be applied to other example chambers and near-field waves. As indicated by FIG. 6, processing circuitry 80 may receive a sensed ventricular integrated bipolar EGM signal and at least one of an identified atrial intrinsic event or an indication of an identified atrial paced event (600). In some examples, ventricular integrated bipolar lead 18 may be configured to sense the ventricular integrated bipolar EGM signal and an atrial lead 22 may be configured to identify an atrial intrinsic event of a patient 14 and / or identify an atrial paced event on the patient 14. In some examples, processing circuitry 80 may be configured to receive an indication of the identified atrial paced event via the atrial lead 22 and / or therapy delivery circuitry 86. In some examples, an indication of the identified atrial paced event may be generated by the processing circuitry 80 itself.

[0081] Processing circuitry 80 may generate a time window of the integrated bipolar EGM signal based on one or more of the identified atrial intrinsic event or the identified atrial paced event (602). For example, processing circuitry 80 may generate a time window of the integrated bipolar EGM signal sensed by the ventricular integrated bipolar lead 18 using the atrial intrinsic event sensed by atrial lead 22. For example, the time window may begin from a pre-atrial event time, such as up to 50 milliseconds (ms) before the identified atrial intrinsic event, and end at a post-atrial event time, such as up to 120 ms after the identified atrial intrinsic event. In some examples, processing circuitry 80 may generate a time window an EGM signal sensed by ventricular integrated bipolar lead 18 using an identified atrial paced event. For example, processing circuitry 80 may generate a time window of the ventricular integrated bipolar EGM signal from the identified atrial pacedevent time to a post-atrial paced event time, such as up to 170 ms after the identified atrial paced event.

[0082] Processing circuitry 80 may determine a value of one or more features of the integrated bipolar EGM signal during the time window (604). In some examples, the one or more features may include one or more of an amplitude of a P-wave of the integrated bipolar EGM signal during the time window, an amplitude of an R-wave of the integrated bipolar EGM signal during the time window, a peak-to-peak amplitude of the integrated bipolar EGM signal during the time window, a maximum peak amplitude of the integrated bipolar EGM signal during the time window, a minimum trough amplitude of the integrated bipolar EGM signal during the time window, a maximum amplitude of a rectified version of the integrated bipolar EGM during the time window, and / or a slew rate of the integrated bipolar EGM signal during the time window. In some examples, the value of the one or more features of the integrated bipolar EGM signal during the time window may correspond to a value of atrial far-field activity sensed by the ventricular integrated bipolar lead 18, e.g., via the integrated bipole of electrodes 42 and 62.

[0083] Processing circuitry 80 may determine whether the value of the one or more features of the windowed portion of the integrated bipolar EGM signal satisfies a far-field activity threshold (606) (e.g., “YES” or “NO”). The far-field activity threshold may be determined based on the current value for the sensitivity threshold. In some examples, the far-field activity threshold may be a P-wave prominence threshold. For example, processing circuitry 80 may calculate the far-field activity threshold by applying a factor to a value of the sensitivity threshold, such as the current value of the sensitivity threshold. In some examples, the factor may be between 0.1 and 1.5. In some examples, the factor may be between 0.7 and 0.9. In other examples, the factor may be a different amount than between 0.7 to 0.9. For example, if the factor is 0.75 (e.g., 75% of the sensitivity threshold), and the value of a feature of the EGM signal, such as an amplitude, is 0.80 (e.g., 80%) of the sensitivity threshold, processing circuitry 80 determines the value of the one or more features of the windowed portion of the integrated bipolar EGM signal (e.g., the amplitude) satisfies the far-field activity (“YES” of 606). For example, if a factor of the sensitivity threshold is 0.75 (e.g., 75% of the sensitivity threshold), and the value of a feature of the integrated bipolar EGM signal, such as P-wave amplitude, is 0.30 (e.g., 30%) of the sensitivity threshold, processing circuitry 80 determines the value of the one or morefeatures of the integrated bipolar EGM signal (e.g., P-wave amplitude) does not satisfy the far-field activity threshold (“NO” of 606).

[0084] In response to processing circuitry 80 determining the value of the one or more features of the windowed portion of the integrated bipolar EGM signal do not satisfy the far-field activity threshold, processing circuitry 80 determines to maintain the sensitivity threshold at its current value (607).

[0085] In response to processing circuitry 80 determining the value of the one or more features of the windowed portion of the integrated bipolar EGM signal satisfies the far-field activity threshold, processing circuitry 80 adjusts the sensitivity threshold from a first value to a second value (608). In some examples, the value of the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold. For example, if the first value of the sensitivity threshold was set to 0.3, processing circuitry 80 may adjust the sensitivity threshold to second value of 0.45.

[0086] In some examples, the windowed portion of the integrated bipolar EGM signal satisfying the far-field activity threshold may indicate the ventricular integrated bipolar lead 18 is oversensing atrial far-field activity, such as due to position or movement of e integrated bipolar lead 18 proximate to an atrium. The ventricular integrated bipolar lead 18 sensing atrial far-field activity above a threshold, such as a sensitivity threshold, may lead to atrial oversensing. Atrial oversensing may lead to a variety of negative issues, such as overdetection of tachyarrhythmias, inhibition of pacing, such as cardiac resynchronization therapy (CRT) and / or loss of optimal AV interval for CRT. In some examples, adjusting a sensitivity threshold, such as in response to determining the value of the one or more features of the windowed portion of the integrated bioplar EGM signal satisfies the far-field activity threshold, may prevent or reduce a likelihood of a integrated bipolar lead in a multichamber device, such as a ventricular integrated bipolar lead 18, from atrial oversensing due to oversensing far-field activity, such as atrial far-field activity, which may reduce overdetection of events such as tachyarrhythmias, inhibition of CRT and / or loss of optimal AV interval for CRT.

[0087] In some examples, generating the time window based on one or more of the atrial intrinsic event or the atrial paced event may focus the determined values of one or more features of integrated bipolar EGM signal to be during the period of time (e.g. time window) in which atrial heart activity is occurring, which may help isolate and indicateatrial oversensing, such as P-wave oversensing, by the ventricular integrated bipolar lead 18. In some examples, to avoid increasing a sensitivity threshold too high, there may be maximum amount a sensitivity threshold may be adjusted (e.g., increased) to minimize risk of under sensing heart event, such as tachyarrhythmias.

[0088] FIG. 7 is a flow diagram illustrating an example technique for operation of a medical system 10 to adjust a sensitivity threshold for detection near field depolarizations in an EGM signal sensed by a ventricular integrated bipolar lead. As indicated by FIG. 7, processing circuitry 80 may receive a sensed ventricular integrated bipolar EGM signal and an indication of at least one of an identified atrial intrinsic event or an identified atrial paced event (700). In some examples, ventricular integrated bipolar lead 18 may be configured to sense the ventricular integrated bipolar EGM signal and atrial lead 22 may be configured to identify an atrial intrinsic event of a patient 14 and / or identify an atrial paced event on the patient 14. In some examples, processing circuitry 80 may be configured to receive an indication of the identified atrial paced event via the atrial lead 22 and / or therapy delivery circuitry 86. In some examples, an indication of the identified atrial paced event may be generated by the processing circuitry 80 itself.

[0089] Processing circuitry 80 may generate a time window of the integrated bipolar EGM signal based on one or more of the identified atrial intrinsic event or the identified atrial paced event (702). For example, the time window may begin from a pre-atrial event time, such as up to 50 milliseconds (ms) before the identified atrial intrinsic event, and end at a post-atrial event time, such as up to 120 ms after the identified atrial intrinsic event. In some examples, processing circuitry 80 may generate a time window the integrated bipolar EGM signal from the identified atrial paced event time to a post-atrial paced event time, such as up to 170 ms after the identified atrial paced event.

[0090] Processing circuitry 80 may determine a value of one or more features of the integrated bipolar EGM signal during the time window (704). Processing circuitry 80 may determine a change in value of one or more features of the integrated bipolar EGM signal during the time window with respect to a baseline value of the respective feature (706). For example, processing circuitry 80 may compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the EGM signal. In some examples, a baseline value for features of the integrated bipolar EGM signal may generatedshortly after a ventricular integrated bipolar lead 18 and atrial lead 22 are implanted in a patient. In some examples, a baseline value for features of the integrated bipolar EGM signal may be predetermined, e.g., a fixed value that is not necessarily patient specific. The baseline values for features of the integrated bipolar EGM signal may be configured to represent measurements of those respective features when the ventricular integrated bipolar lead 18 senses a minimal amount of atrial far-field activity.

[0091] In some examples, the one or more features may include one or more of an amplitude of a P-wave of the integrated bipolar EGM signal during the time window, an amplitude of R-wave of the integrated bipolar EGM signal during the time window, a peak- to-peak amplitude of the integrated bipolar EGM signal during the time window, a maximum peak amplitude of the integrated bipolar EGM signal during the time window, a minimum trough amplitude of the integrated bipolar EGM signal during the time window, a maximum amplitude of a rectified version of the integrated bipolar EGM during the time window, and / or a slew rate of the integrated bipolar EGM signal during the time window. In some examples, the value of the one or more features of the integrated EGM signal during the time window may correspond to a value of atrial far-field activity sensed by the ventricular integrated bipolar lead 18, e.g., via an integrated bipole of electrodes 42 and 66.

[0092] Processing circuitry 80 may determine whether a change in value of the one or more features of the windowed portion of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the EGM signal satisfies the threshold (708) (e.g., “YES” or “NO”). The far-field activity threshold and its comparison to the one or more feature of the windowed portion of the integrated bipolar EGM signal may be as described above with respect to 606 of FIG. 6.

[0093] In some examples, the change threshold may be between a 10% to 50% change from the baseline value. For example, if the change threshold is 10% of the baseline value, and if the value of a feature of the windowed portion of the integrated bipolar EGM signal, such as P-wave amplitude, is more than 10% different than the baseline value (e.g., more than 10% greater P-wave amplitude than baseline P-wave amplitude), the change in value of the one or more features of the EGM signal satisfy the change threshold (“YES” of 708). For example, if the change threshold is 10% of the baseline value, and if the value of a feature of the windowed portion of the integrated bipolar EGM signal, such as P-wave amplitude, is less than 10% different than the baseline value (e.g., less than 10% differencein P-wave amplitude than baseline P-wave amplitude), the change in value of the one or more features of the windowed portion of the integrated bipolar EGM signal does not satisfy the change threshold (“NO” of 708).

[0094] In response to processing circuitry 80 determining the value of the one or more features of the EGM signal does not satisfy the far-field activity threshold and / or the change in value of the one or more features of the windowed portion of the integrated bipolar EGM signal do not satisfy the change threshold, processing circuitry 80 determines to maintain the sensitivity threshold at its current value (709).

[0095] In response to processing circuitry 80 determining the change in value of the one or more features of the windowed portion of the integrated bipolar EGM signal satisfy the change threshold and the value of the one or more features of the windowed portion of the integrated bipolar EGM signal satisfy the far-field activity threshold, processing circuitry 80 adjusts the sensitivity threshold from a first value to a second value (710). In some examples, the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold. For example, if the first value of the sensitivity threshold was set to 0.3, processing circuitry 80 may adjust the sensitivity threshold to a second value of 0.45. In some examples, the windowed portion of the integrated bipolar EGM signal satisfying the far-field activity threshold may indicate the ventricular integrated bipolar lead 18 is oversensing atrial far-field activity, such as due to position or movement of integrated bipolar lead 18 proximate to an atrium. The ventricular integrated bipolar lead 18 sensing atrial far-field activity above a threshold, such as a sensitivity threshold, may lead to atrial oversensing. Atrial oversensing may lead to a variety of negative issues, such as overdetection of tachyarrhythmias, inhibition of CRT and / or loss of optimal AV interval for CRT. In some examples, adjusting a sensitivity threshold, such as in response to determining the change in value of the one or more feature(s) of the windowed portion of the integrated bipolar EGM signal satisfy the change threshold and determining the value of the one or more features of the windowed portion of the integrated bipolar EGM signal EGM signal satisfies far-field activity threshold, may prevent or reduce a likelihood of an integrated bipolar lead to oversensing far-field activity, such as atrial far-field activity. In some examples, to avoid increasing a sensitivity threshold too high, there may be maximum amount a sensitivity threshold may be adjusted (e.g., increased) to minimize risk of under sensing heart event, such as tachyarrhythmias.

[0096] In one or more examples, the functions described in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on, as one or more instructions or code, a computer-readable medium and executed by a hardware -based processing unit. Computer- readable media may include computer-readable storage media forming a tangible, non- transitory medium. Instructions may be executed by one or more processing circuitries, such as one or more DSPs, ASICs, FPGAs, general purpose microprocessors, or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processing circuitry,” as used herein may refer to one or more of any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.

[0097] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuitry, as well as any combinations of such components, embodied in external devices, such as physician or patient programmers, stimulators, or other devices. The terms “processor” and “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry, and alone or in combination with other digital or analog circuitry.

[0098] For aspects implemented in software, at least some of the functionality ascribed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

[0099] In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components. Also, the techniques could be fully implemented in one or more circuits or logic elements. The techniques of this disclosuremay be implemented in a wide variety of devices or apparatuses, including an IMD, an external programmer, a combination of an IMD and external programmer, an integrated circuit (IC) or a set of ICs, and / or discrete electrical circuitry, residing in an IMD and / or external programmer.

[0100] Various aspects of the techniques may enable the following examples.

[0101] Example 1: A system includes an implantable medical device (IMD) configured to: obtain an integrated bipolar electrogram (EGM) signal of first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; and at least one of: identify an intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber; or identify a paced event of the second chamber sensed via the second lead; processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far- field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the IMD from a first value to a second value.

[0102] Example 2 : The system of example 1, wherein the processing circuitry is further configured to: compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determine the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjusting the sensitivity threshold comprises adjusting the sensitivity threshold based on determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

[0103] Example 3: The system of any of examples 1-2, wherein the first chamber is a ventricle of the heart and the second chamber is an atrium of the heart.

[0104] Example 4 : The system of any of examples 1-3, wherein the one or more features of the integrated bipolar EGM signal include at least one of a P-wave amplitude of the integrated bipolar EGM signal, a peak-to-peak amplitude of the integrated bipolar EGMsignal, a maximum peak amplitude of the integrated bipolar EGM signal, a minimum trough amplitude of the integrated bipolar EGM signal, or a slew rate of the integrated bipolar EGM signal.

[0105] Example 5 : The system of example 4, wherein the one or more features of the EGM signal include a P-wave amplitude of the integrated bipolar EGM signal.

[0106] Example 6 : The system of any of examples 1-5, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

[0107] Example 7 : The system of any of examples 1-6, wherein the far-field activity threshold is based on the first value of the sensitivity threshold.

[0108] Example 8 : The system of example 7, wherein the far-field activity threshold is based on applying a factor to the first value of the sensitivity threshold.

[0109] Example 9: The system of example 8, wherein the factor is between 0.7 and 0.9.

[0110] Example 10: The system of any of examples 1-9, wherein the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold.

[0111] Example 11: The system of example 10, wherein the second value of the sensitivity threshold is at least 50% greater than the first value of the sensitivity threshold.

[0112] Example 12: The system of any of examples 1-11, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the intrinsic event.

[0113] Example 13: The system of example 12, wherein the time window begins at a pre-intrinsic event time and ends at a post-intrinsic event time, wherein the pre-intrinsic event time is before the intrinsic event and the post-intrinsic event time is after the intrinsic event.

[0114] Example 14: The system of example 13, wherein the pre-intrinsic event time is up to 50 milliseconds before the intrinsic event and the post-intrinsic event time is up to 120 milliseconds after the intrinsic event.

[0115] Example 15: The system of any of examples 1-11, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the paced event.

[0116] Example 16: The system of example 15, wherein the time window begins at a time of the paced event and ends at a pre-determined time after the paced event.

[0117] Example 17: The system of example 16, wherein the pre-determined time is up to 170 milliseconds.

[0118] Example 18: The system of any of examples 1-17, further includes the first lead configured to be implanted within the first chamber of the heart; and the second lead configured to be implanted in the second chamber of the heart.

[0119] Example 19: The system of any of examples 1-18, wherein the first lead is an integrated bipolar lead comprising two electrodes configured to respectively serve as an anode and cathode of a sensing bipole.

[0120] Example 20: An implantable medical device includes sensing circuitry configured to: obtain an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber, wherein the first lead comprises an integrated bipolar lead; and identify an intrinsic event of a second chamber of the heart sensed via a second lead implanted in the second chamber; therapy delivery circuitry configured to perform a paced event on the second chamber of the heart via the second lead; and processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the sensing circuitry from a first value to a second value.

[0121] Example 21: The implantable medical device of example 20, wherein the processing circuitry is further configured to: compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determine the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjusting the sensitivity threshold comprises adjusting the sensitivity threshold based on determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

[0122] Example 22: The implantable medical device of any of examples 20-21, wherein the first chamber is a ventricle of the heart and the second chamber is an atrium of the heart.

[0123] Example 23: The implantable medical device of any of examples 20-22, wherein the one or more features of the integrated bipolar EGM signal include at least one of a P- wave amplitude of the integrated bipolar EGM signal, a peak-to-peak amplitude of the integrated bipolar EGM signal, a maximum peak amplitude of the integrated bipolar EGM signal, a minimum trough amplitude of the integrated bipolar EGM signal, or a slew rate of the integrated bipolar EGM signal.

[0124] Example 24: The implantable medical device of example 23, wherein the one or more features of the EGM signal include a P-wave amplitude of the integrated bipolar EGM signal.

[0125] Example 25: The implantable medical device of any of examples 20-24, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

[0126] Example 26: The implantable medical device of any of examples 20-25, wherein the far-field activity threshold is based on the first value of the sensitivity threshold.

[0127] Example 27: The implantable medical device of example 26, wherein the far- field activity threshold is based on applying a factor to the first value of the sensitivity threshold.

[0128] Example 28: The implantable medical device of example 27, wherein the factor is between 0.7 and 0.9.

[0129] Example 29: The implantable medical device of any of examples 20-28, wherein the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold.

[0130] Example 30: The implantable medical device of example 29, wherein the second value of the sensitivity threshold is at least 50% greater than the first value of the sensitivity threshold.

[0131] Example 31: The implantable medical device of any of examples 20-30, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the intrinsic event.

[0132] Example 32: The implantable medical device of example 31, wherein the time window begins at a pre-intrinsic event time and ends at a post-intrinsic event time, wherein the pre-intrinsic event time is before the intrinsic event and the post-intrinsic event time is after the intrinsic event.

[0133] Example 33: The implantable medical device of example 32, wherein the pre- intrinsic event time is up to 50 milliseconds before the intrinsic event and the post-intrinsic event time is up to 120 milliseconds after the intrinsic event.

[0134] Example 34: The implantable medical device of any of examples 20-30, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the paced event.

[0135] Example 35: The implantable medical device of example 34, wherein the time window begins at a time of the paced event and ends at a pre-determined time after the paced event.

[0136] Example 36: The implantable medical device of example 35, wherein the predetermined time is up to 170 milliseconds.

[0137] Example 37: The implantable medical device any of examples 20-36, further includes the first lead configured to be implanted within the first chamber of the heart; and the second lead configured to be implanted in the second chamber of the heart.

[0138] Example 38: The implantable medical device of any of examples 20-36, wherein the first lead is an integrated bipolar lead comprising two electrodes configured to respectively serve as an anode and cathode of a sensing bipole.

[0139] Example 39: A method includes receiving an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; receiving at least one of an identified intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber or an identified paced event of the second chamber sensed via the second lead; generating a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determining a value of one or more features of the integrated bipolar EGM signal during the time window; determining the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and in response to determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold,adjust a sensitivity threshold of an implantable medical device from a first value to a second value.

[0140] Example 40: The method of example 39, the method further includes comparing the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjusting the sensitivity threshold comprises adjusting the sensitivity threshold based on determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

[0141] Example 41: The method of any of examples 39-40, wherein the first chamber is a ventricle of the heart and the second chamber is an atrium of the heart.

[0142] Example 42: The method of any of examples 39-41, wherein the one or more features of the integrated bipolar EGM signal include at least one of a P-wave amplitude of the integrated bipolar EGM signal, a peak-to-peak amplitude of the integrated bipolar EGM signal, a maximum peak amplitude of the integrated bipolar EGM signal, a minimum trough amplitude of the integrated bipolar EGM signal, or a slew rate of the integrated bipolar EGM signal.

[0143] Example 43: The method of example 42, wherein the one or more features of the EGM signal include a P-wave amplitude of the integrated bipolar EGM signal.

[0144] Example 44: The method of any of examples 39-43, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

[0145] Example 45: The method of any of examples 39-44, wherein the far-field activity threshold is based on the first value of the sensitivity threshold.

[0146] Example 46: The method of example 45, wherein the far-field activity threshold is based on applying a factor to the first value of the sensitivity threshold.

[0147] Example 47: The method of example 46, wherein the factor is between 0.7 and 0.9.

[0148] Example 48: The method of any of examples 39-47, wherein the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold.

[0149] Example 49: The method of example 48, wherein the second value of the sensitivity threshold is up to 50% greater than the first value of the sensitivity threshold.

[0150] Example 50: The method of any of examples 39-49, the method further includes generating the time window of the integrated bipolar EGM signal based on the intrinsic event.

[0151] Example 51: The method of example 50, wherein the time window begins at a pre-intrinsic event time and ends at a post-intrinsic event time, wherein the pre-intrinsic event time is before the intrinsic event and the post-intrinsic event time is after the intrinsic event.

[0152] Example 52: The method of example 51, wherein the pre-intrinsic event time is up to 50 milliseconds before the intrinsic event and the post-intrinsic event time is up to 120 milliseconds after the intrinsic event.

[0153] Example 53: The method of any of examples 39-49, the method further includes generating the time window of the integrated bipolar EGM signal based on the paced event.

[0154] Example 54: The method of example 53, wherein the time window begins at a time of the paced event and ends at a pre-determined time after the paced event.

[0155] Example 55: The method of example 54, wherein the pre-determined time is up to 170 milliseconds.

[0156] Example 56: The method of any of examples 39-55, wherein the first lead is an integrated bipolar lead comprising two electrodes configured to respectively serve as an anode and cathode of a sensing bipole.

[0157] Example 57: A non-transitory computer-readable storage medium storing instructions, which when executed, cause processing circuitry to: receive an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; receive at least one of an identified intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber or an identified paced event of the second chamber sensed via the second lead; generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and in response to determiningthe value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of an implantable medical device from a first value to a second value.

[0158] Example 58: The storage medium of example 57, wherein the processing circuitry is further caused to: compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determine the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjust the sensitivity threshold from the first value to the second value comprises to adjust the sensitivity threshold based on determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

[0159] Example 59: The storage medium of any of examples 57-58, wherein the first chamber is a ventricle of the heart and the second chamber is an atrium of the heart.

[0160] Example 60: The storage medium of any of examples 57-59, wherein the one or more features of the integrated bipolar EGM signal include at least one of a P-wave amplitude of the integrated bipolar EGM signal, a peak-to-peak amplitude of the integrated bipolar EGM signal, a maximum peak amplitude of the integrated bipolar EGM signal, a minimum trough amplitude of the integrated bipolar EGM signal, or a slew rate of the integrated bipolar EGM signal.

[0161] Example 61: The storage medium of example 60, wherein the one or more features of the EGM signal include a P-wave amplitude of the integrated bipolar EGM signal.

[0162] Example 62: The storage medium of any of examples 57-61, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

[0163] Example 63: The storage medium of any of examples 57-62, wherein the far- field activity threshold is based on the first value of the sensitivity threshold.

[0164] Example 64: The storage medium of example 63, wherein the far-field activity threshold is based on applying a factor to the first value of the sensitivity threshold.

[0165] Example 65: The storage medium of example 64, wherein the factor is between 0.7 and 0.9.

[0166] Example 66: The storage medium of any of examples 57-65, wherein the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold.

[0167] Example 67: The storage medium of example 66, wherein the second value of the sensitivity threshold is up to 50% greater than the first value of the sensitivity threshold.

[0168] Example 68: The storage medium of any of examples 57-67, wherein the processing circuitry is further caused to: generate the time window of the integrated bipolar EGM signal based on the intrinsic event.

[0169] Example 69: The storage medium of example 68, wherein the time window begins at a pre-intrinsic event time and ends at a post-intrinsic event time, wherein the pre- intrinsic event time is before the intrinsic event and the post-intrinsic event time is after the intrinsic event.

[0170] Example 70: The storage medium of example 69, wherein the pre-intrinsic event time is up to 50 milliseconds before the intrinsic event and the post-intrinsic event time is up to 120 milliseconds after the intrinsic event.

[0171] Example 71: The storage medium of any of examples 57-67, wherein the processing circuitry is further caused to: generate the time window of the integrated bipolar EGM signal based on the paced event.

[0172] Example 72: The storage medium of example 71, wherein the time window begins at a time of the paced event and ends at a pre-determined time after the paced event.

[0173] Example 73: The storage medium of example 72, wherein the pre-determined time is up to 170 milliseconds.

[0174] Example 74: The storage medium of any of examples 57-73, wherein the first lead is an integrated bipolar lead comprising two electrodes configured to respectively serve as an anode and cathode of a sensing bipole.

[0175] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

CLAIMS:

1. A system comprising: an implantable medical device (IMD) configured to: obtain an integrated bipolar electrogram (EGM) signal of first chamber of a heart of a patient sensed via a first lead implanted in the first chamber; and at least one of: identify an intrinsic event of a second chamber of the heart of the patient sensed via a second lead implanted in the second chamber; or identify a paced event of the second chamber sensed via the second lead; processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the identified paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolar EGM signal satisfies a far-field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the IMD from a first value to a second value.

2. The system of claim 1, wherein the processing circuitry is further configured to: compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determine the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjusting the sensitivity threshold comprises adjusting the sensitivity threshold based on determining the change in value of the one or more features of theintegrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

3. The system of any of claims 1-2, wherein the first chamber is a ventricle of the heart and the second chamber is an atrium of the heart.

4. The system of any of claims 1-3, wherein the one or more features of the integrated bipolar EGM signal include at least one of a P-wave amplitude of the integrated bipolar EGM signal, a peak-to-peak amplitude of the integrated bipolar EGM signal, a maximum peak amplitude of the integrated bipolar EGM signal, a minimum trough amplitude of the integrated bipolar EGM signal, or a slew rate of the integrated bipolar EGM signal.

5. The system of any of claims 1-4, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

6. The system of any of claims 1-5, wherein the far-field activity threshold is based on the first value of the sensitivity threshold.

7. The system of any of claims 1-6, wherein the second value of the sensitivity threshold is greater than the first value of the sensitivity threshold.

8. The system of any of claims 1-7, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the intrinsic event.

9. The system of any of claims 1-7, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the paced event.

10. The system of any of claims 1-9, further comprising: the first lead configured to be implanted within the first chamber of the heart; and the second lead configured to be implanted in the second chamber of the heart.

11. An implantable medical device comprising: sensing circuitry configured to: obtain an integrated bipolar electrogram (EGM) signal of a first chamber of a heart of a patient sensed via a first lead implanted in the first chamber, wherein the first lead comprises an integrated bipolar lead; and identify an intrinsic event of a second chamber of the heart sensed via a second lead implanted in the second chamber; therapy delivery circuitry configured to perform a paced event on the second chamber of the heart via the second lead; and processing circuitry configured to: generate a time window of the integrated bipolar EGM signal of the first chamber based on one or more of the identified intrinsic event or the paced event of the second chamber; determine a value of one or more features of the integrated bipolar EGM signal during the time window; determine the value of the one or more features of the integrated bipolarEGM signal satisfies a far-field activity threshold; and based on determining the value of the one or more features of the EGM signal satisfies the far-field activity threshold, adjust a sensitivity threshold of the sensing circuitry from a first value to a second value.

12. The implantable medical device of claim 11, wherein the processing circuitry is further configured to: compare the value of the one or more features of the integrated bipolar EGM signal to a respective baseline value of the one or more features to determine a change in value of the one or more features of the integrated bipolar EGM signal; and determine the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold, wherein adjusting the sensitivity threshold comprises adjusting the sensitivity threshold based on determining the change in value of the one or more features of the integrated bipolar EGM signal satisfies a change threshold and the value of the one or more features of the integrated bipolar EGM signal satisfies the far-field activity threshold.

13. The implantable medical device of any of claims 11-12, wherein the value of the one or more features of the integrated bipolar EGM signal corresponds to a value of far-field activity of the second chamber sensed via the first lead in the first chamber.

14. The implantable medical device of any of claims 11-13, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the intrinsic event.

15. The implantable medical device of any of claims 11-13, wherein the processing circuitry is configured to generate the time window of the integrated bipolar EGM signal based on the paced event.

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