Apparatus for cardiac event signal sensing

Abstract

A medical device is configured to sense a first cardiac signal and a second cardiac signal, and determine a quantitative relationship of a first characteristic of the first cardiac signal and a second characteristic of the second cardiac signal. The medical device is configured to confirm a sensed cardiac event signal and / or discard an oversensing signal based on the quantitative relationship.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 368,241, filed on July 12, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a medical device configured to sense cardiac event signals and to distinguish between sensed cardiac event signals and cross-chamber over-sensed cardiac event signals. Background Art

[0004] During normal sinus rhythm (NSR), the heartbeat is regulated by electrical signals generated by the sinoatrial (SA) node located in the wall of the right atrium. Each atrial depolarization signal generated by the SA node spreads in the atria, causing depolarization and contraction of the atria, and reaches the atrioventricular (AV) node. The AV node responds by propagating the ventricular depolarization signal through the bundle of His of the ventricular septum and thereafter to the bundle branches and Purkinje muscle fibers of the right and left ventricles (sometimes referred to as the "His-Purkinje system").

[0005] Patients with conduction system abnormalities, such as SA node disorder or AV node poor conduction, bundle branch obstruction or other conduction abnormalities may receive a pacemaker to restore a more normal heart rhythm. A single-chamber pacemaker connected to a transvenous lead carrying an electrode located in the right atrium can provide atrial pacing to treat patients with SA node dysfunction. When the AV node functions normally, single-chamber atrial pacing can fully correct the heart rhythm. The atrial depolarization induced by pacing can be normally conducted to the ventricles through the AV node and the His-Purkinje system, maintaining normal AV synchronization. However, some patients may experience conduction abnormalities of the AV node, such as partial or complete AV block. AV block can be intermittent and can evolve over time. In the case of high AV block, atrial depolarization may not be conducted to the ventricles in every atrial cycle, or may be conducted with a prolonged AV conduction time, resulting in poor AV synchronization of the native rhythm. In this case, the patient may need a single-chamber ventricular pacemaker or a dual-chamber pacemaker.

[0006] A dual-chamber pacemaker may be implanted in certain patients to pace both the atrial and ventricular chambers and maintain AV synchronization. The dual-chamber pacemaker may be coupled to a transvenous atrial lead and a transvenous ventricular lead to place electrodes for sensing and pacing in both the atrial and ventricular chambers. The pacemaker itself may be implanted in a subcutaneous pocket, with the transvenous lead tunneled to the subcutaneous pocket.

[0007] It has been proposed or suggested that intracardiac pacemakers be implanted entirely within a patient's heart, thereby eliminating the need for a transvenous lead. For example, an intracardiac pacemaker can provide sensing and pacing from within a cardiac chamber of a patient suffering from a conduction abnormality to promote a more normal heart rhythm. Summary of the invention

[0008] The technology of the present disclosure generally relates to a medical device configured to sense cardiac event signals associated with myocardial depolarization. The medical device can receive cardiac electrical signals from electrodes implanted in or on a cardiac chamber and sense cardiac event signals from the cardiac electrical signals. The medical device can be a pacemaker configured to sense P waves associated with atrial depolarization and / or R waves associated with ventricular depolarization. The medical device can be capable of generating cardiac pacing pulses. The timing of the generated cardiac pacing pulses can be controlled by the medical device based on the sensed cardiac event signals.

[0009] A medical device operating according to the techniques disclosed herein can sense a cardiac event signal from a received cardiac electrical signal and determine whether the sensed cardiac event signal corresponds to a first cardiac chamber (e.g., an atrium or a ventricle) or a second cardiac chamber (e.g., a ventricle or an atrium). If the second cardiac event signal is not sensed within a confirmation delay time interval, it can be confirmed that the first cardiac event signal is generated from the first cardiac chamber. If the second cardiac event signal is sensed during the confirmation delay time interval and the ratio, difference, or other quantitative relationship between a feature of the first cardiac event signal and a feature of the second cardiac event signal meets a confirmation threshold for confirming the first cardiac event signal, it can be confirmed that the first cardiac event signal is generated from the first cardiac chamber. If the second cardiac event signal is sensed during the confirmation delay time interval and the quantitative relationship between the features of the first cardiac event signal and the second cardiac event signal does not meet the confirmation threshold required to confirm the first cardiac event signal, it can be confirmed that the first cardiac event signal is generated from the second cardiac chamber.

[0010] In one example, the present disclosure provides a medical device, the medical device including a sensing circuit, the sensing circuit configured to sense a first cardiac signal and a second cardiac signal. The medical device includes a control circuit, the control circuit configured to receive a first event signal of the first cardiac signal from the sensing circuit and receive a second event signal of the second cardiac signal from the sensing circuit. The control circuit can be configured to determine a quantitative relationship between a first feature of the first cardiac signal and a second feature of the second cardiac signal, and confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship.

[0011] In another example, the present disclosure provides a method comprising: sensing a first cardiac signal and a second cardiac signal; receiving a first event signal of the first cardiac signal; receiving a second event signal of the second cardiac signal; determining a quantitative relationship between a first feature of the first cardiac signal and a second feature of the second cardiac signal; and confirming that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship.

[0012] In another example, the present disclosure provides a non-transitory computer-readable storage medium comprising a set of instructions which, when executed by a control circuit of a medical device, causes the medical device to perform the following operations: sensing a first cardiac signal and a second cardiac signal; receiving a first event signal of the first cardiac signal; receiving a second event signal of the second cardiac signal; determining a quantitative relationship between a first feature of the first cardiac signal and a second feature of the second cardiac signal; and confirming, based on the quantitative relationship, that the sensed cardiac event signal is one of the first event signal or the second event signal.

[0013] This article also discloses the subject matter of the following articles:

[0014] Clause 1. A medical device, the medical device comprising: a sensing circuit, the sensing circuit configured to sense a first cardiac signal and a second cardiac signal; and a control circuit, the control circuit configured to receive a first event signal of the first cardiac signal from the sensing circuit and a second event signal of the second cardiac signal from the sensing circuit. The control circuit can also be configured to determine a quantitative relationship between a first feature of the first cardiac signal and a second feature of the second cardiac signal, and to confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship.

[0015] Item 2. A medical device according to Item 1, wherein the control circuit is further configured to schedule cardiac pacing pulses at one of a first pacing interval or a second pacing interval different from the first pacing interval: in response to confirming that the sensed cardiac event signal is the first cardiac event signal, scheduling the cardiac pacing pulse at the first pacing interval; or in response to confirming that the sensed cardiac event signal is the second cardiac event signal, scheduling the cardiac pacing pulse at the second pacing interval.

[0016] Clause 3. The medical device of Clause 2, further comprising a pulse generator configured to deliver the cardiac pacing pulses scheduled at one of the first pacing interval or the second pacing interval.

[0017] Clause 4. A medical device according to any one of clauses 1 to 3, wherein the sensing circuit is further configured to: sense a first cardiac event signal in response to the first cardiac signal crossing a first sensing threshold; generate the first event signal received by the control circuit; sense a second cardiac event signal in response to the second cardiac electrical signal crossing a second sensing threshold; and generate the second event signal received by the control circuit.

[0018] Clause 5. A medical device according to any one of clauses 1 to 4, wherein the control circuit is further configured to confirm the sensed cardiac event signal based on the quantitative relationship by: comparing the quantitative relationship with a first confirmation threshold; in response to the quantitative relationship satisfying the first confirmation threshold, confirming that the sensed cardiac event signal is the first cardiac event signal; or in response to the quantitative relationship not satisfying the first confirmation threshold, confirming that the sensed cardiac event signal is the second cardiac event signal.

[0019] Clause 6. A medical device according to any one of clauses 1 to 5, wherein the control circuit is further configured to: receive the first event signal as an atrial event signal; receive the second event signal as a ventricular event signal; and when the first event signal is the atrial event signal, compare the quantitative relationship with a P-wave confirmation threshold. The control circuit can also be configured to confirm the sensed cardiac event signal based on the quantitative relationship by: in response to the quantitative relationship being less than the P-wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal; or in response to the quantitative relationship being greater than the P-wave confirmation threshold, confirming that the sensed cardiac event signal is a ventricular event signal.

[0020] Clause 7. A medical device according to any one of clauses 1 to 5, wherein the control circuit is further configured to: receive the first event signal as a ventricular event signal; receive the second event signal as an atrial event signal; and when the first event signal is the ventricular event signal, compare the quantitative relationship with an R-wave confirmation threshold. The control circuit can also be configured to confirm the sensed cardiac event signal based on the quantitative relationship by: confirming that the sensed cardiac event signal is the ventricular event signal in response to the quantitative relationship being greater than the R-wave confirmation threshold; or confirming that the sensed cardiac event signal is the atrial event signal in response to the quantitative relationship being less than the R-wave confirmation threshold.

[0021] Clause 8. A medical device according to any one of clauses 1 to 5, wherein the control circuit is further configured to confirm the sensed cardiac event signal based on the quantitative relationship by: comparing the quantitative relationship with a P wave confirmation threshold and an R wave confirmation threshold; and confirming that the sensed cardiac event signal is one of an atrial event signal or a ventricular event signal: in response to the quantitative relationship being closer to the P wave confirmation threshold than the R wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal; or in response to the quantitative relationship being closer to the R wave confirmation threshold than the P wave confirmation threshold, confirming that the sensed cardiac event signal is the ventricular event signal.

[0022] Clause 9. A medical device according to any one of clauses 1 to 8, wherein the control circuit is further configured to determine the quantitative relationship by determining the first characteristic as the maximum peak amplitude of the first cardiac signal and determining the second characteristic as the maximum peak amplitude of the second cardiac signal.

[0023] Clause 10. The medical device of any one of clauses 1 to 9, wherein the control circuit is further configured to initiate one or more blanking periods and / or one or more refractory periods based on the confirmed sensed cardiac event signal.

[0024] Clause 11. A medical device according to any one of clauses 1 to 10, wherein the control circuit is also configured to adjust at least one of the following items: a first low-pass filter cutoff frequency applied by the sensing circuit to the first cardiac signal; a first high-pass filter cutoff frequency applied by the sensing circuit to the first cardiac signal; a second low-pass filter cutoff frequency applied by the sensing circuit to the second cardiac signal; and / or a second high-pass filter cutoff frequency applied by the sensing circuit to the second cardiac signal.

[0025] Clause 12. A medical device according to clause 11, wherein the control circuit is further configured to determine a first quantitative relationship between the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the first event signal from the sensing circuit without receiving the second event signal within a confirmation delay time from the first event signal. The control circuit may determine a second quantitative relationship between the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the second event signal from the sensing circuit without receiving the first event signal within a confirmation delay time from the first event signal. The control circuit may determine a difference between the first quantitative relationship and the second quantitative relationship; and adjust at least one of the first low-pass filter cutoff frequency, the first high-pass filter cutoff frequency, the second low-pass filter cutoff frequency, and / or the second high-pass filter cutoff frequency to maximize the difference between the first quantitative relationship and the second quantitative relationship.

[0026] Clause 13. A medical device according to any one of Clauses 1 to 12, wherein the control circuit is further configured to: determine that the second cardiac event signal is received within a confirmation delay time from the first cardiac event signal; and determine the quantitative relationship in response to receiving the second cardiac event signal within the confirmation delay time.

[0027] Item 14. A medical device according to Item 13, wherein the control circuit is further configured to schedule pacing pulses by: starting a pacing interval based on which of the first cardiac event signal or the second cardiac event signal is confirmed; and adjusting the pacing interval by one of the confirmation delay time or the time since the second cardiac event signal.

[0028] Clause 15. The medical device of any one of Clauses 1 to 14, wherein the sensing circuit comprises a first sensing circuit configured to receive the first cardiac signal and a second sensing circuit configured to receive the second cardiac signal.

[0029] Clause 16. The medical device of any one of Clauses 1 to 15, wherein the control circuit is further configured to determine the quantitative relationship as a ratio of the first characteristic and the second characteristic.

[0030] Clause 17. A medical device according to any one of clauses 1 to 15, wherein the control circuit is further configured to determine the quantitative relationship as one of: a ratio of the first characteristic and the second characteristic; a difference between the first characteristic and the second characteristic; a sum of the first characteristic and the second characteristic; or a product of the first characteristic and the second characteristic.

[0031] Clause 18. A medical device according to any one of clauses 1 to 17, wherein the control circuit is further configured to set a first confirmation threshold by: receiving the first event signal from the sensing circuit without receiving the second event signal within a confirmation delay time from the first event signal; determining a first reference quantitative relationship between the first feature of the first cardiac signal and the second feature of the second cardiac signal when the first event signal is received from the sensing circuit without receiving the second event signal within the confirmation delay time from the first event signal; and setting the first confirmation threshold based on the first reference quantitative relationship. The control circuit can also be configured to confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on a comparison of the quantitative relationship with the first confirmation threshold.

[0032] Clause 19. A medical device according to clause 18, wherein the control circuit is further configured to set a second confirmation threshold by: receiving the second event signal from the sensing circuit without receiving the first event signal within a confirmation delay time from the second event signal; determining a second reference quantitative relationship between the first feature of the first cardiac signal and the second feature of the second cardiac signal when the first event signal is received from the sensing circuit without receiving the second event signal within a confirmation delay time from the first event signal; and setting the second confirmation threshold based on the second reference quantitative relationship. The control circuit can confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on a comparison of the quantitative relationship with at least one of the first confirmation threshold or the second confirmation threshold.

[0033] Clause 20. The medical device of any one of clauses 1 to 17, wherein the control circuit is further configured to confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on a comparison of the quantitative relationship to a confirmation threshold. The control circuit may also be configured to adjust the confirmation threshold based on the first cardiac signal and the second cardiac signal.

[0034] Clause 21. A medical device according to any one of clauses 1 to 20, the medical device further comprising a pulse generator configured to generate a pacing pulse. The control circuit is further configured to: initiate a pacing escape interval to schedule a pending pacing pulse; initiate a confirmation delay in response to receiving the first event signal; determine that the pacing escape interval expires during the confirmation delay; and delay the pending pacing pulse in response to determining that the pacing escape interval expires during the confirmation delay. The control circuit is further configured to: confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship, and control the pulse generator to deliver or inhibit the delayed pending pacing pulse according to whether the sensed cardiac event signal is confirmed as the first event signal or the second event signal.

[0035] Clause 22. A medical device according to any one of clauses 1 to 20, further comprising a pulse generator configured to generate a pacing pulse. The control circuit may also be configured to: initiate a pacing escape interval to schedule a pending pacing pulse; and after initiating the pacing escape interval, receive a next event signal from the sensing circuit after confirming the sensed cardiac event signal. The control circuit may initiate a confirmation delay in response to receiving the next event signal. The control circuit may determine that the pacing escape interval expires before the confirmation delay expires and before another event signal is received from the sensing circuit. In response to the pacing escape interval expiring during the confirmation delay before receiving another event signal from the sensing circuit, the control circuit may control the pulse generator to deliver the scheduled pending pacing pulse when the pacing escape interval expires.

[0036] Clause 23. The medical device of Clause 22, wherein the control circuit is further configured to initiate the pacing escape interval in response to the confirmed sensed cardiac event signal.

[0037] Clause 24. A medical device according to Clause 22, wherein the pulse generator is further configured to deliver a first pacing pulse before receiving the next event signal, and the control circuit is further configured to initiate the pacing escape interval to schedule the pending pacing pulse in response to the pulse generator delivering the first pacing pulse.

[0038] Clause 25. A medical device according to any one of clauses 21 to 24, further comprising a pulse generator configured to deliver a previous pacing pulse before the control circuit receives the first event signal. The control circuit is further configured to initiate a polarization delay in response to the pulse generator delivering the previous pacing pulse. The control circuit may also be configured to detect expiration of the polarization delay and, when a first event signal is received after expiration of the polarization delay, initiate the confirmation delay in response to the first event signal.

[0039] Item 26. A method, the method comprising: sensing a first cardiac signal and a second cardiac signal; receiving a first event signal of the first cardiac signal; receiving a second event signal of the second cardiac signal; determining a quantitative relationship between a first characteristic of the first cardiac signal and a second characteristic of the second cardiac signal; and confirming that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship.

[0040] Clause 27. The method according to Clause 26, further comprising: scheduling a cardiac pacing pulse at one of a first pacing interval or a second pacing interval different from the first pacing interval: in response to confirming that the sensed cardiac event signal is the first cardiac event signal, scheduling the cardiac pacing pulse at the first pacing interval; or in response to confirming that the sensed cardiac event signal is the second cardiac event signal, scheduling the cardiac pacing pulse at the second pacing interval.

[0041] Clause 28. The method of Clause 27, further comprising delivering the cardiac pacing pulse scheduled at one of the first pacing interval or the second pacing interval.

[0042] Clause 29. A method according to any one of clauses 26 to 28, the method further comprising: sensing a first cardiac event signal in response to the first cardiac signal crossing a first sensing threshold; generating the first event signal in response to sensing the first cardiac event signal; sensing a second cardiac event signal in response to the second cardiac electrical signal crossing a second sensing threshold; and generating the second event signal in response to sensing the second cardiac event signal.

[0043] Clause 30. A method according to any one of Clauses 26 to 29, wherein confirming the sensed cardiac event signal based on the quantitative relationship includes: comparing the quantitative relationship with a first confirmation threshold; in response to the quantitative relationship satisfying the first confirmation threshold, confirming that the sensed cardiac event signal is the first event signal; or in response to the quantitative relationship not satisfying the first confirmation threshold, confirming that the sensed cardiac event signal is the second event signal.

[0044] Clause 31. A method according to any one of clauses 26 to 30, the method further comprising: receiving the first event signal as an atrial event signal; receiving the second event signal as a ventricular event signal; when the first event signal is the atrial event signal, comparing the quantitative relationship with a P wave confirmation threshold; and confirming the sensed cardiac event signal based on the quantitative relationship by: in response to the quantitative relationship being less than the P wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal; or in response to the quantitative relationship being greater than the P wave confirmation threshold, confirming that the sensed cardiac event signal is the ventricular event signal.

[0045] Clause 32. A method according to any one of clauses 26 to 30, the method further comprising: receiving the first event signal as a ventricular event signal; receiving the second event signal as an atrial event signal; when the first cardiac event signal is a ventricular event signal, comparing the quantitative relationship with an R-wave confirmation threshold; and confirming the sensed cardiac event signal based on the quantitative relationship by: in response to the quantitative relationship being greater than the R-wave confirmation threshold, confirming that the sensed cardiac event signal is the ventricular event signal; or in response to the quantitative relationship being less than the R-wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal.

[0046] Clause 33. A method according to any one of clauses 26 to 30, wherein confirming the sensed cardiac event signal based on the quantitative relationship includes: comparing the quantitative relationship with a P wave confirmation threshold and an R wave confirmation threshold; and confirming that the sensed cardiac event signal is one of an atrial event signal or a ventricular event signal: in response to the quantitative relationship being closer to the P wave confirmation threshold than the R wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal; or in response to the quantitative relationship being closer to the R wave confirmation threshold than the P wave confirmation threshold, confirming that the sensed cardiac event signal is the ventricular event signal.

[0047] Clause 34. The method of any one of clauses 26 to 33, further comprising determining the quantitative relationship by determining the first feature as a maximum peak amplitude of the first cardiac signal and determining the second feature as a maximum peak amplitude of the second cardiac signal.

[0048] Clause 35. The method of any one of clauses 26 to 34, further comprising initiating one or more blanking periods and / or one or more refractory periods based on the confirmed sensed cardiac event signal.

[0049] Clause 36. A method according to any one of clauses 26 to 35, the method further comprising adjusting at least one of: a first low-pass filter cutoff frequency applied to the first cardiac signal; a first high-pass filter cutoff frequency applied to the first cardiac signal; a second low-pass filter cutoff frequency applied to the second cardiac signal; and / or a second high-pass filter cutoff frequency applied to the second cardiac signal.

[0050] Clause 37. A method according to clause 36, the method further comprising: determining a first quantitative relationship between the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the first event signal from the sensing circuit without receiving the second event signal within a confirmation delay time from the first event signal; determining a second quantitative relationship between the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the second event signal from the sensing circuit without receiving the first event signal within a confirmation delay time from the first event signal. The method may also include: determining a difference between the first quantitative relationship and the second quantitative relationship; and adjusting at least one of the first low-pass filter cutoff frequency, the first high-pass filter cutoff frequency, the second low-pass filter cutoff frequency and / or the second high-pass filter cutoff frequency to maximize the difference between the first quantitative relationship and the second quantitative relationship.

[0051] Clause 38. A method according to any one of clauses 26 to 37, the method further comprising: determining that the second cardiac event signal is received within a confirmation delay time from the first cardiac event signal; and determining the quantitative relationship in response to receiving the second cardiac event signal within the confirmation delay time.

[0052] Clause 39. A method according to clause 38, wherein the control circuit is further configured to schedule pacing pulses by: starting a pacing interval based on which of the first cardiac event signal or the second cardiac event signal is confirmed; and adjusting the pacing interval by one of the confirmation delay time or the time since the second cardiac event signal.

[0053] Clause 40. The medical device of any one of Clauses 26 to 39, further comprising determining the quantitative relationship as a ratio of the first feature and the second feature.

[0054] Clause 41. A medical device according to any one of clauses 26 to 39, further comprising determining the quantitative relationship as one of: a ratio of the first feature and the second feature, a difference between the first feature and the second feature; a sum of the first feature and the second feature; or a product of the first feature and the second feature.

[0055] Clause 42. A method according to any one of clauses 26 to 41, the method further comprising: setting a first confirmation threshold by: receiving the first event signal from the sensing circuit without receiving the second event signal within a confirmation delay time from the first event signal; determining a first reference quantitative relationship between the first feature of the first cardiac signal and the second feature of the second cardiac signal when the first event signal is received from the sensing circuit without receiving the second event signal within the confirmation delay time from the first event signal; and setting the first confirmation threshold based on the first reference quantitative relationship. The method may also include confirming that the sensed cardiac event signal is one of the first event signal or the second event signal based on a comparison of the quantitative relationship with the first confirmation threshold.

[0056] Clause 43. A method according to clause 42, the method further comprising: setting a second confirmation threshold by: receiving the second event signal from the sensing circuit without receiving the first event signal within a confirmation delay time from the second event signal; determining a second reference quantitative relationship between the first feature of the first cardiac signal and the second feature of the second cardiac signal when the first event signal is received from the sensing circuit without receiving the first event signal within the confirmation delay time from the first event signal; and setting the second confirmation threshold based on the second reference quantitative relationship. The method may include confirming that the sensed cardiac event signal is one of the first event signal or the second event signal based on a comparison of the quantitative relationship with at least one of the first confirmation threshold or the second confirmation threshold.

[0057] Clause 44. The method of any one of clauses 26 to 41, further comprising confirming the sensed cardiac event signal as one of the first event signal or the second event signal based on a comparison of the quantitative relationship to a first confirmation threshold. The method may further comprise adjusting the confirmation threshold based on the first cardiac signal and the second cardiac signal.

[0058] Clause 45. A method according to any one of clauses 26 to 44, the method further comprising: initiating a pacing escape interval to schedule a pending pacing pulse; initiating a confirmation delay in response to receiving the first event signal; determining that the pacing escape interval expires during the confirmation delay; and delaying the pending pacing pulse in response to determining that the pacing escape interval expires during the confirmation delay. The method further comprises: confirming that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship; and controlling the pulse generator to deliver or inhibit the delayed pending pacing pulse according to whether the sensed cardiac event signal is confirmed as the first event signal or the second event signal.

[0059] Clause 46. A method according to any one of clauses 26 to 44, the method further comprising: initiating a pacing escape interval to schedule a pending pacing pulse; and after initiating the pacing escape interval, receiving a next event signal after confirming the sensed cardiac event signal. The method may also include: initiating a confirmation delay in response to receiving the next event signal; determining that the pacing escape interval expires before the confirmation delay expires and before another event signal is received. In response to the pacing escape interval expiring during the confirmation delay before receiving another event signal, the method may also include delivering the scheduled pending pacing pulse at the expiration of the pacing escape interval.

[0060] Clause 47. The method of Clause 46, further comprising initiating the pacing escape interval in response to the confirmed sensed cardiac event signal.

[0061] Clause 48. The method of clause 46, further comprising: delivering a first pacing pulse prior to receiving the next event signal; and initiating the pacing escape interval to schedule the pending pacing pulse in response to delivering the first pacing pulse.

[0062] Clause 49. A method according to any one of clauses 45 to 48, the method further comprising: delivering a previous pacing pulse before receiving the first event signal; initiating a polarization delay in response to the pulse generator delivering the previous pacing pulse; detecting expiration of the polarization delay; and initiating the confirmation delay in response to the first event signal when the first event signal is received after expiration of the polarization delay.

[0063] Clause 50. A non-transitory computer-readable storage medium storing a set of instructions that, when executed by control circuitry of a medical device, cause the medical device to: sense a first cardiac signal and a second cardiac signal; receive a first event signal of the first cardiac signal; receive a second event signal of the second cardiac signal; and determine a quantitative relationship between a first feature of the first cardiac signal and a second feature of the second cardiac signal. The instructions may also cause the medical device to confirm that the sensed cardiac event signal is one of the first event signal or the second event signal based on the quantitative relationship.

[0064] The details of one or more aspects of the present disclosure are set forth in the following drawings and description. Other features, objectives, and advantages of the techniques described in the present disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a conceptual diagram illustrating an implantable medical device (IMD) system that may be used to sense cardiac signals and provide cardiac pacing.

[0066] Figure 2 Based on an example Figure 1 Conceptual diagram of a pacemaker shown.

[0067] Figure 3 Based on an example Figure 1 A conceptual diagram of an exemplary configuration of a pacemaker.

[0068] Figure 4 is a conceptual diagram of a sensing circuit that may be included in a pacemaker according to one example.

[0069] Figure 5 is a flow chart of a method executable by a pacemaker for confirming sensed cardiac event signals and identifying cross-chamber oversensing (CCOS) event signals.

[0070] Figure 6 is a timing diagram of an atrial electrogram (EGM) signal, a ventricular EGM signal, and a sensed event marker channel according to some examples, which depicts cardiac sensed event signals that can be confirmed as real events or identified as CCOS events by a pacemaker.

[0071] Figure 7 is a conceptual diagram of sensing operating states of a pacemaker according to some examples.

[0072] Figure 8 is a graph of atrial and ventricular EGM signals that may be sensed by a pacemaker.

[0073] Fig. 9 is a flow chart of a method that may be performed by a pacemaker for establishing or updating a P-wave confirmation threshold and / or an R-wave confirmation threshold according to some examples.

[0074] Fig.10 is a flow chart of a method for establishing a bandpass filter cutoff frequency for sensing atrial EGM signals and ventricular EGM signals according to some examples.

[0075] Fig.11 is a flow chart of a method that may be performed by a medical device for confirming a sensed cardiac event signal according to another example.

[0076] Fig.12 is a flow chart of a method for sensing cardiac event signals by a medical device and providing pacing and / or sensing responses to the sensed cardiac event signals according to another example.

[0077] Figures 13 to 17 is a diagram of various examples of pacing responses that a medical device may perform when a pacing escape interval expires during an acknowledgement delay period. DETAILED DESCRIPTION

[0078] In general, the present disclosure describes a medical device and method for determining when a cardiac event signal generated from a cardiac chamber (e.g., an atrial chamber or a ventricular chamber) is erroneously over-sensed as a cardiac event signal generated from a different cardiac chamber (e.g., a ventricular chamber or an atrial chamber). An over-sensed cardiac event signal (which may be a true atrial P wave that is over-sensed as a false ventricular R wave or a true ventricular R wave that is over-sensed as a false atrial P wave) can be identified by a processing circuit of a medical device according to the techniques disclosed herein. Sensing an atrial electrical event as a false R wave or sensing a ventricular electrical event as a false P wave is referred to herein as "cross-chamber over-sensing." Cross-chamber over-sensing (CCOS) may cause a medical device to incorrectly determine a patient's heart rhythm or heart rate. CCOS may interfere with the timing and control of a cardiac electrical stimulation therapy delivered by a medical device. For example, CCOS may cause a medical device to suppress an electrical stimulation pulse (e.g., a cardiac pacing pulse or other therapeutic electrical stimulation pulse) when an electrical stimulation pulse is actually needed or to deliver an electrical stimulation pulse when an electrical stimulation pulse is not actually needed. Thus, the technology disclosed herein provides improvements in the areas of cardiac rhythm monitoring and cardiac therapy delivery by improving the cardiac event signal sensing capabilities of medical devices.

[0079] Figure 1 is a conceptual diagram showing an implantable medical device (IMD) system 10 that can be used to sense cardiac signals and provide cardiac pacing. The IMD system 10 shown includes a pacemaker 14 that is implanted in the right atrium (RA) of a patient's heart. In some examples, the pacemaker 14 is a transcatheter leadless pacemaker that can be implanted entirely within a cardiac chamber. The size of the pacemaker 14 can be reduced compared to a subcutaneously implanted pacemaker and its shape can be generally cylindrical to facilitate transvenous implantation via a delivery catheter. The pacemaker 14 can be a leadless pacemaker that includes electrodes carried on the pacemaker housing without the need for medical electrical leads extending from the pacemaker 14 for sensing cardiac electrical signals and delivering cardiac pacing pulses.

[0080] The pacemaker 14 may be capable of sensing atrial event signals and ventricular event signals, such as a P wave accompanying atrial depolarization and an R wave accompanying ventricular depolarization. The pacemaker 14 may be configured as a dual-chamber pacemaker, which is capable of sensing both atrial event signals and ventricular event signals and delivering atrial pacing pulses and ventricular pacing pulses as needed based on the sensed atrial event signals and / or ventricular event signals. In yet other examples, the pacemaker 14 may be configured as a single-chamber pacemaker, which is capable of delivering only atrial pacing pulses or is capable of delivering only ventricular pacing pulses, but is still capable of dual-chamber sensing of both atrial event signals and ventricular event signals. In yet other examples, the pacemaker 14 may be configured to sense and pace a single cardiac chamber (an atrial chamber or a ventricular chamber).

[0081] In the example shown, the pacemaker 14 is implanted in the RA for providing ventricular pacing from an atrial location. The pacemaker 14 can be configured to deliver ventricular pacing pulses from the RA approach via the heart's natural conduction system and / or ventricular muscle. For example, the distal end of the pacemaker 14 can be positioned at the lower end of the atrial septum, below the AV node, and near the tricuspid annulus to position the tip electrode 164 for advancement into the atrial septum toward the His bundle of the natural His-Purkinje system. A second electrode (e.g., a ring electrode 162 or a ring electrode 165) can be spaced proximally from the tip electrode 164 so as to be used with the tip electrode 164 for bipolar pacing of the right and left ventricles via the His-Purkinje system and / or ventricular muscle. The ventricular pacing pulses delivered by the pacemaker 14 can capture at least a portion of the His bundle and / or ventricular muscle for delivering ventricular pacing to the ventricles (e.g., the right ventricle (RV) and / or the left ventricle (LV)) from the atrial implantation location of the pacemaker 14. However, the techniques disclosed herein are not necessarily limited to a specific implantation location of the pacemaker 14 and may be implemented in pacemakers implanted in a variety of surgical locations to provide cardiac signal sensing of atrial events and / or ventricular events and, in at least some examples, deliver cardiac pacing to at least one cardiac chamber.

[0082] The pacemaker 14 may be capable of bidirectional wireless communication with an external device 20 for programming sensing and pacing control parameters. Aspects of the external device 20 may generally correspond to the external programming / monitoring unit disclosed in U.S. Pat. No. 5,507,782 (Kieval et al.), the entire contents of which are incorporated herein by reference. The external device 20 is often referred to as a "programmer" because it is often used by a physician, technician, nurse, clinician, or other qualified user to program operating parameters in an implanted medical device. The external device 20 may be located in a clinic, hospital, or other medical facility. The external device 20 may alternatively be embodied as a home monitor or handheld device that can be used in a medical facility, in a patient's home, or in another location. Operating parameters including sensing and therapy delivery control parameters may be programmed into the pacemaker 14 by a user interacting with the external device 20.

[0083] The external device 20 may include a processor 52, a memory 53, a display unit 54, a user interface 56, and a telemetry unit 58. The processor 52 controls the external device operation and processes data and signals received from the pacemaker 12 or 14. The display unit 54 may generate a display of data and information related to the pacemaker function to the user (the display may include a graphical user interface) for reviewing pacemaker operation and programming parameters. The display unit 54 may generate a display including cardiac signals and / or data derived therefrom, cardiac pacing timing markers, cardiac pacing history, and / or other physiological data, patient data, or device-related data that may be stored by the pacemaker 14 and transmitted to the external device 20 during an interrogation session. For example, the pacemaker 14 may generate outputs for transmission to the external device 20 including pacing and sensing event history, device operating parameters, and device diagnostic data.

[0084] The transmitted data may include cardiac electrical signal segments generated by the pacemaker sensing circuitry including markers indicating pacing pulse delivery and sensed cardiac event signals, such as ventricular sensed event signals and / or atrial sensed event signals and any delivered atrial pacing pulses and / or ventricular pacing pulses. The display unit 54 may display cardiac electrical signal segments with annotated sensed event signals, pacing pulse markers, and / or identified over-sensing event signals.

[0085] The user interface 56 may include a mouse, touch screen, keyboard, etc. to enable a user to interact with the external device 20 to initiate a telemetry session with the pacemaker 14 to retrieve data from and / or transmit data to the pacemaker 14, including programmable parameters for controlling sensing and pacing functions. The telemetry unit 58 includes a transceiver and antenna configured for bidirectional communication with telemetry circuitry included in the pacemaker 14, and is configured to operate in conjunction with the processor 52 to send and receive data related to pacemaker functions over the communication link 24.

[0086] The telemetry unit 58 and the pacemaker 14 can establish a wireless two-way communication link 24. The communication link 24 can be implemented using a wireless communication system such as The external device 20 may be configured to establish a wireless communication link 24 using a Wi-Fi, Medical Implant Communications Service (MICS), or other radio frequency (RF) link of a communications bandwidth. In some examples, the external device 20 may include a programming header that is placed proximate to the pacemaker 14 to establish and maintain the communications link 24, and in other examples, the external device 20 and the pacemaker 14 may be configured to communicate using a distance telemetry algorithm and circuitry that does not require the use of a programming header and does not require user intervention to maintain the communications link.

[0087] It is contemplated that the external device 20 may be wired or wirelessly connected to a communication network via telemetry circuitry including a transceiver and antenna or via hardwired communication lines for transmitting data to a centralized database or computer to allow remote management of the patient. A remote patient management system including a centralized patient database may enable a clinician to view data related to the sensing and pacing functions performed by the pacemaker 14.

[0088] Figure 2 Based on an example Figure 1 10. Conceptual diagram of a pacemaker 14 shown. The pacemaker 14 includes a housing 150 having a distal end 102 and a proximal end 104. The lateral sidewalls 170 of the housing 150 extending from the distal end 102 to the proximal end 104 can be generally cylindrical to facilitate transvenous delivery, for example, via a catheter. The distal end 102 is referred to as "distal" because it is expected to be the leading end when the pacemaker 14 is advanced through a delivery tool (such as a catheter) and placed against a target pacing site. In other examples, the housing 150 may have a generally prismatic shape. The housing 150 encloses electronics and power supplies for sensing cardiac signals, generating pacing pulses, and controlling therapy delivery, as well as other functions of the pacemaker 14 as described herein.

[0089] The pacemaker 14 is shown to include electrodes 162, 164, and 165 for sensing cardiac electrical signals and delivering pacing pulses spaced apart along a housing 150 of the pacemaker 14. Electrode 164 is shown to include a tip electrode extending from the distal end 102 of the housing 150. Electrodes 162 and 165 are shown as ring electrodes along a lateral sidewall 170 of the housing 150. Electrodes 162 and 165 may be ring electrodes surrounding the lateral sidewall 170, for example adjacent to the proximal end 104 and adjacent to the distal end 102, respectively.

[0090] Electrode 164 is shown as a screw-in helical electrode that can provide fixation of the pacemaker 14 at the implant site and act as a pacing and sensing electrode. Electrode 164 can be advanced from within the right atrial cavity to a ventricular pacing site, for example, for delivery of pacing to the His-Purkinje conduction system and / or for pacing of the ventricular septal myocardial tissue.

[0091] Tip electrode 164 may serve as a cathode electrode, while ring electrode 162 serves as a return anode for delivering ventricular pacing pulses. Tip electrode 164 and ring electrode 162 may serve as a bipolar pair for ventricular pacing and for receiving ventricular electrical signals from which R waves may be sensed by a sensing circuit enclosed by housing 150. Ring electrodes 162 and 165 may form a second anode and cathode pair for bipolar atrial pacing and sensing atrial electrical signals from which P waves may be sensed by a sensing circuit enclosed by housing 150. Electrodes 162, 164, and 165 may be, but are not limited to, titanium, platinum, iridium, or alloys thereof, and may include low polarization coatings such as titanium nitride, iridium oxide, ruthenium oxide, platinum black, and the like.

[0092] Electrodes 162, 164, and 165 may be positioned at locations along the pacemaker 14 other than as shown. Examples of various pacing electrode arrangements for providing cardiac pacing along the native conduction system of the heart and / or ventricular muscle are generally disclosed in U.S. Publication No. 2019 / 0083779 (Yang et al., issued as U.S. Pat. No. 11,426,578) and U.S. Pat. No. 11,007,369 (Sheldon et al.), both of which are incorporated herein by reference in their entirety.

[0093] When the tip electrode 164 and the ring electrode 162 are used to sense ventricular R waves from the RA implantation location, the atrial P waves may be over-sensed as false R waves. When the ring electrodes 162 and 165 are used to sense atrial P waves, the far-field R waves may be over-sensed as false P waves. These types of cross-chamber pacing may occur when the electrodes used to sense cardiac electrical signals from one cardiac chamber are in close proximity to another cardiac chamber, for example, when the pacemaker 14 is positioned in the RA for delivering ventricular pacing. As described herein, in some examples, the pacemaker 14 can be configured to sense both P waves and R waves to control ventricular pacing pulse delivery in various pacing modes, which pacing modes may include both atrial synchronous ventricular pacing modes and asynchronous pacing modes. Regardless of whether the pacemaker 14 is configured to sense ventricular R waves, atrial P waves, or both, the pacemaker 14 can be configured to confirm the sensed cardiac event signals according to the techniques disclosed herein to avoid CCOS event signals interfering with the scheduling and delivery of cardiac pacing pulses according to the operating pacing mode.

[0094] The housing 150 is formed of a biocompatible material, such as stainless steel or a titanium alloy. In some examples, the housing 150 may include an insulating coating. Examples of insulating coatings include polyparaxylene, urethane, PEEK, or polyimide, among others. The entirety of the housing 150 may be insulated, but only the electrodes 162, 164, and 165 are not insulated. The tip electrode 164 may act as a cathode electrode and may be coupled to an internal circuit enclosed by the housing 150, such as a pacing pulse generator and a cardiac electrical signal sensing circuit, via an electrical feedthrough across the housing 150. The electrodes 162 and 165 may be formed as conductive portions of the housing 150 that define respective annular electrodes that are electrically isolated from each other and from other portions of the housing 150, such as Figure 2 In the figure, the overall structure is shown.

[0095] The pacemaker 14 may include features for facilitating deployment and fixation at the implantation site. For example, the pacemaker 14 may optionally include a delivery tool interface 158. The delivery tool interface 158 may be positioned at the proximal end 104 of the pacemaker 14 and configured to be connected to a delivery device (such as a catheter) that is used to position the pacemaker 14 at the implantation site during the implantation procedure. The delivery tool interface may enable a clinician to advance, retract, and guide the pacemaker 14 to the implantation site and rotate the pacemaker 14 to advance the spiral tip electrode 164 into the cardiac tissue. The spiral tip electrode 164 provides fixation of the pacemaker 14 at the implantation site in this example. However, in other examples, the pacemaker 14 may include a set of fixed prongs or other fixed members to fix the pacemaker 14 to the cardiac tissue. Various types of active and / or passive fixed members may be used to anchor or stabilize the pacemaker 14 in the implantation site.

[0096] Figure 3 is a conceptual diagram of an exemplary configuration of a pacemaker 14 according to some examples. The pacemaker 14 may include a pulse generator 202, a cardiac electrical signal sensing circuit 204, a control circuit 206, a telemetry circuit 208, a memory 210, a motion sensor 212, and a power source 214. Figure 3 The various circuits represented may be combined on one or more integrated circuit boards including: application specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated, or grouped) and memories that execute one or more software or firmware programs, combinational logic circuits, state machines, or other suitable components that provide the described functionality.

[0097] The cardiac electrical signal sensing circuit 204 (hereinafter referred to as the "sensing circuit" 204) is configured to receive at least one cardiac electrical signal via electrodes coupled to the pacemaker 14 (for example, via the tip electrode 164 and the ring electrode 162). When the ring electrode 165 is present, another cardiac electrical signal can be received via the electrodes 162 and 165 and / or the electrodes 164 and 165. Therefore, the sensing circuit 204 can have multiple sensing channels, for example, an atrial sensing channel 203 and a ventricular sensing channel 205. Although the pacemaker 14 is shown as having three electrodes in the example shown herein, in other examples, the pacemaker 14 can be provided with two electrodes or more than three electrodes, which can be coupled to the sensing circuit 204 (and / or the pulse generator 202) to form a selected sensing (and / or pacing) electrode vector. The sensing circuit 204 may include a switching circuit for coupling a pair of sensing electrodes to a corresponding sensing channel 203 or 205. As described below in conjunction with Figure 4 As described, the sensing channels 203 and 205 may include filters, amplifiers, analog-to-digital converters (ADCs), rectifiers, sense amplifiers, comparators, and / or other circuits for sensing cardiac event signals (e.g., P waves and / or R waves) and generating sensed cardiac event signals (e.g., atrial sensed event signals (Asense signals) and ventricular sensed event signals (Vsense signals)) that are transmitted to the control circuit 206. The sensing circuit 204 may be configured to transmit filtered and amplified multi-bit digital electrocardiogram (EGM) signals from one or both of the atrial sensing channel 203 and the ventricular sensing channel 205 to the control circuit 206, for example. The EGM signals may be processed and analyzed by the control circuit 206 to determine the cardiac rhythm and / or stored in the memory 210 as cardiac signal segments, which may be transmitted by the telemetry circuit 208 to, for example, an external device 20 ( Figure 1 ).

[0098] The control circuit 206 may include a pacing timing circuit 242 and a processor 244. Figure 4 As described above, the control circuit 206 can receive the Vsense signal and the Asense signal from the sensing circuit 204 for controlling the timing of the cardiac pacing pulse. In response to the ventricular sensing channel 205 sensing the ventricular event signal, the Vsense signal can be transmitted from the sensing circuit 204 to the control circuit 206 to indicate the timing of the suspected R wave. In response to the atrial sensing channel 203 sensing the atrial event signal, the Asense signal can be transmitted from the sensing circuit 204 to the control circuit 206 to indicate the timing of the suspected P wave.

[0099] Processor 244 may communicate sensing control parameters to sensing circuit 204 for use in sensing cardiac event signals from cardiac electrical signals. For example, one or more blanking periods, refractory periods, atrial sensitivity, ventricular sensitivity, and other control parameters used by sensing circuit 204 to apply a sensing threshold amplitude for sensing cardiac event signals may be communicated from processor 244 to sensing circuit 204. Techniques for sensing cardiac event signals and confirming that the sensed cardiac event signals are atrial event signals or ventricular event signals are further described below.

[0100] The processor 244 may include one or more clocks for generating a clock signal that is used by the pacing timing circuit 242 to count down various pacing intervals to provide ventricular pacing according to the operating pacing mode. Depending on the operating pacing mode of the control circuit 206, the pacing timing circuit 242 may initiate a pacing interval to schedule a pacing pulse. The control circuit 206 may be configured to operate in a variety of programmable and / or automatically switchable pacing modes. During an atrial synchronous ventricular pacing mode (e.g., which may be represented as a DDD or VDD pacing mode), a ventricular pacing pulse may be delivered synchronously with an atrial pacing pulse and a received Asense signal. For example, in response to receiving an Asense signal, the pacing timing circuit 242 may initiate an AV pacing interval to control the timing of an atrial synchronous ventricular pacing pulse. When a ventricular pacing pulse is delivered by the pulse generator 202 at the expiration of the AV pacing interval, the pacing timing circuit 242 may initiate a ventricular pacing interval to schedule a ventricular pacing pulse. During atrial-synchronous ventricular pacing, if an Asense signal is not received before the ventricular pacing interval expires, the pulse generator 202 may deliver an asynchronous pacing pulse and restart the ventricular pacing interval. If an Asense signal is received (or an atrial pacing pulse is delivered) before the ventricular pacing interval expires, the scheduled ventricular pacing pulse may be suppressed. The pending pacing pulse may be canceled, and an atrial-synchronous triggered ventricular pacing pulse may be delivered at the AV pacing interval from the Asense signal (or the delivered atrial pacing pulse). In some examples, the restart of the scheduled pacing pulse or pacing interval may be delayed as a pending pacing pulse until the received Asense or Vsense signal is confirmed or determined to be a CCOS signal based on analysis of the cardiac signal according to the techniques disclosed herein.

[0101] In response to receiving the Vsense signal from the sensing circuit 204, the pacing timing circuit 242 can inhibit a pending ventricular pacing pulse scheduled at the ventricular pacing interval (or scheduled at the AV pacing interval) and restart the ventricular pacing interval. The ventricular pacing interval can be a lower rate interval (LRI) corresponding to a programmed minimum or basal ventricular pacing rate. In other cases, the ventricular pacing interval can be a temporary ventricular pacing interval set to a rate smoothing interval to avoid sudden changes in the ventricular rate. In other cases, the ventricular pacing interval can be a temporary rate-responsive pacing interval set to provide rate-responsive pacing during periods of increased physical activity of the patient, which can be determined based on a signal from the motion sensor 212, as further described below.

[0102] Pulse generator 202 generates electrical pacing pulses that can be delivered to pace the ventricles of the patient's heart via cathode electrode 164 and return anode electrode 162. In an example that includes atrial pacing capability, pulse generator 202 can generate electrical pacing pulses for pacing the atria, for example, using electrodes 165 and 162. In addition to providing control signals to pacing timing circuit 242 and pulse generator 202 for controlling the timing of pacing pulses, processor 244 can also retrieve programmable pacing control parameters from memory 210, such as pacing pulse amplitude and pacing pulse width, which are passed to pulse generator 202 for controlling pacing pulse delivery.

[0103] The pulse generator 202 may include a charging circuit 230, a switching circuit 232, and an output circuit 234. The charging circuit 230 is configured to receive current from the power supply 214 and may include a holding capacitor that may be charged to a pacing pulse amplitude, for example, under the control of a voltage regulator included in the charging circuit 230. The pacing pulse amplitude may be set based on a control signal from the control circuit 206. The switching circuit 232 may control when the holding capacitor of the charging circuit 230 is coupled to the output circuit 234 for delivery of a pacing pulse. For example, the switching circuit 232 may include a switch that is activated by a timing signal received from the pacing timing circuit 242 when a pacing escape interval expires and remains closed within a programmed pacing pulse width to enable the holding capacitor of the charging circuit 230 to discharge. During the programmed pacing pulse duration, the holding capacitor, which is pre-charged to the pacing pulse voltage amplitude, may be discharged across the electrodes 164 and 162 (or 165 and 162) through the output capacitor of the output circuit 234. Examples of pacing circuits generally disclosed in U.S. Pat. No. 5,507,782 (Kieval et al.) and U.S. Pat. No. 8,532,785 (Crutchfield et al.) (the entire contents of both patents are incorporated herein by reference) can be implemented in the pacemaker 14 to charge the pacing capacitor to a predetermined pacing pulse amplitude and deliver pacing pulses under the control of the control circuit 206.

[0104] It should be understood that when the pacemaker 14 is configured for dual chamber pacing, the pulse generator 202 can be configured to deliver both atrial pacing pulses and ventricular pacing pulses under the control of the pacing timing circuit 242. The atrial pacing pulses are generated by the pulse generator 202 according to the atrial pacing pulse amplitude and pulse width. The ventricular pacing pulses are generated by the pulse generator 202 according to the ventricular pacing pulse amplitude and pulse width. The pulse generator 202 can include an atrial pacing channel and a ventricular pacing channel that can be separately controlled to deliver an atrial pacing pulse at the expiration of an atrial pacing interval and to deliver a ventricular pacing pulse at the expiration of an AV pacing interval and / or a ventricular pacing interval. The separate atrial pacing channel and ventricular pacing channel can include some shared circuitry for generating and delivering pacing pulses. For example, the atrial pacing channel and the ventricular pacing channel may include a shared output circuit that is selectively coupled to the appropriate pacing electrode pairs via a switching circuit included in the output circuit 234.

[0105] The pacemaker 14 may include a motion sensor 212, such as an accelerometer, for sensing patient motion. The motion sensor 212 may include a single-axis or multi-axis accelerometer for generating acceleration signals in one or more dimensions, which can be used to determine the relative level of the patient's physical activity. In some examples, the pacemaker 14 may be capable of delivering rate-responsive pacing based on a patient physical activity metric determined based on the acceleration signal generated by the motion sensor 212. The control circuit 206 may receive a rectified acceleration signal from the motion sensor 212 and determine the patient's physical activity metric based on the acceleration signal, for example by summing the amplitude of the acceleration signal sample points within the activity metric time interval. The activity metric may be converted to a target heart rate to meet the patient's metabolic needs. The target heart rate may be converted to an SIR based on a SIR (sensor indicated rate) transfer function, which, for example, includes a lower rate set point and a daily living activities (ADL) range and a maximum higher rate. During the rate-responsive pacing mode, the pulse generator 202 may be controlled by the control circuit 206 to deliver atrial pacing pulses or ventricular pacing pulses at a rate-responsive pacing rate determined based on the SIR. An example of a method for providing rate-responsive pacing based on an acceleration signal is generally disclosed in U.S. Pat. No. 9,724,518 (Sheldon et al.), the entire contents of which are incorporated herein by reference.

[0106] The memory 210 may include computer-readable instructions that, when executed by the control circuit 206, cause the control circuit 206 to perform various functions attributed to the pacemaker 14 throughout the present disclosure. The computer-readable instructions may be encoded within the memory 210. The memory 210 may include any non-transitory computer-readable storage medium, including any volatile, non-volatile, magnetic, optical, or electronic medium, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, or other digital media, with the sole exception of transient propagating signals.

[0107] The memory 210 can store sensed event data based on the Vsense signal and Asense signal received from the sensing circuit 204, and can mark the Vsense signal and / or Asense signal as a false event signal when it is identified as a CCOS event signal according to the technology disclosed herein. In some examples, the memory 210 includes a buffer for storing one or more EGM signal segments received from the sensing circuit 204. When a CCOS event signal is identified, the memory 210 can store one or more EGM signal segments. The CCOS event signal history and representative EGM signal segments can be stored in the memory 210 for transmission via the telemetry circuit 208.

[0108] Telemetry circuit 208 includes a transceiver 209 and an antenna 211 for transmitting and receiving data via a radio frequency (RF) communication link. As described above, telemetry circuit 208 may be capable of communicating with external device 20 ( Figure 1 ) for two-way communication. Cardiac electrical signals and / or data derived therefrom, such as sensed event signals, may be transmitted by telemetry circuitry 208 to external device 20. Programmable control parameters and algorithms for sensing cardiac event signals and for confirming sensed event signals and identifying CCOS event signals and for controlling pacing therapy delivered by pulse generator 202 may be received by telemetry circuitry 208 and stored in memory 210 for access by control circuitry 206.

[0109] The power source 214 provides power to each of the other circuits and components of the pacemaker 14 as needed. The power source 214 may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. For clarity, the connections between the power source 214 and the other pacemaker circuits and components are not shown. Figure 3 , but should be Figure 3 The power supply 214 can provide power to the pulse generator 202, the sensing circuit 204, the telemetry circuit 208, the memory 210, and the motion sensor 212 as needed.

[0110] The functions attributed to the pacemaker 14 herein may be embodied as one or more processors, controllers, hardware, firmware, software, or any combination thereof. The depiction of different features as specific circuits is intended to highlight different functional aspects and does not necessarily imply that such functions must be implemented by separate hardware, firmware, or software components or by any particular circuit architecture. Instead, the functionality associated with one or more circuits described herein may be performed by separate hardware, firmware, or software components, or integrated within general hardware, firmware, or software components. For example, a process for confirming a cardiac event signal may be implemented in a control circuit 206 that executes instructions stored in a memory 210 and relies on inputs from a sensing circuit 204. In view of the disclosure herein, it is within the capabilities of those skilled in the art to provide software, hardware, and / or firmware to accomplish the described functionality in the context of any modern pacemaker.

[0111] Figure 41 is a conceptual diagram of a sensing circuit for a pacemaker 14 according to some examples. The sensing circuit 204 may include an atrial sensing channel 203 and a ventricular sensing channel 205. The atrial sensing channel 203 is shown as receiving raw cardiac electrical signals from electrodes 165 and 162. The ventricular sensing channel 205 is shown as receiving raw cardiac electrical signals from electrodes 164 and 162. However, it should be understood that other sensing electrode vectors may be provided as inputs to the sensing channels 203 and / or 205, depending on which electrodes are coupled to or included on the pacemaker housing 150 and which sensing electrode vectors provide the greatest sensitivity for sensing P waves and R waves and the greatest distinction between true P waves and true R waves. For example, in some examples, the ventricular sensing channel 205 may receive raw cardiac electrical signals from electrodes 164 and 165.

[0112] The raw cardiac electrical signal is received as an input to the pre-filter and amplifier circuit 220 or 250 of the atrial sensing channel 203 or the ventricular sensing channel 205, respectively. The pre-filter and amplifier circuit 220 and 250 can each include a high-pass filter to remove DC offset, such as a high-pass filter of 2.5 Hz to 5 Hz, or a wideband filter with a bandpass of 2.5 Hz to 100 Hz or narrower to remove DC offset and high-frequency noise. The pre-filter and amplifier circuit 220 and 250 can also include an amplifier to amplify the raw cardiac electrical signal delivered to the corresponding ADC 222 or 252.

[0113] The ADC 222 can pass the rectified digital signal to the filter 224 of the atrial sensing channel 203. The filter 224 can be a bandpass filter with a bandpass cutoff frequency for passing the P wave signal and attenuating other cardiac event signals (e.g., R wave and T wave). In some examples, the high-pass and / or low-pass cutoff frequencies of the filter 224 are user programmable and / or can be adjusted by the control circuit 206 to reduce the incidence of CCOS of far-field R waves by the atrial sensing channel 203 and / or improve the distinction between true sensed event signals and CCOS event signals. The atrial EGM signal 225 filtered according to the different cutoff frequency settings applied by the filter 224 can be passed to the control circuit 206 for selecting the optimal bandpass cutoff frequency of the filter 224 to facilitate reliable sensing of the atrial P wave. In other examples, the output of the ADC 222 can be passed to the control circuit 206 for analysis to select the optimal low-pass and high-pass cutoff frequencies of the filter 224. The following is combined with Fig.10A method for selecting high-pass and low-pass filter frequencies is described. As an example, the low-pass cutoff frequency of filter 224 may be between 25 Hz and 100 Hz or between 50 and 80 Hz, and the high-pass cutoff frequency may be between 5 Hz and 25 Hz or between 15 Hz and 20 Hz. In one example, filter 224 has a low-pass frequency of 70 Hz and a high-pass frequency of 17 Hz.

[0114] The atrial event detector 226 may include a sense amplifier, a comparator, or other event detection circuit that compares the incoming rectified, filtered, and amplified atrial EGM signal to a P-wave sensing threshold. For example, when the incoming signal crosses the P-wave sensing threshold, the atrial event detector 226 generates an atrial sensed event signal (Asense) 228 that can be transmitted to the control circuit 206. The P-wave sensing threshold can be an automatically adjusted threshold that is automatically reduced by the sensing circuit 204 from a starting value to a minimum value or until a P-wave sensing threshold crossing occurs. The P-wave sensing threshold amplitude is initially set to a starting value applied to the atrial EGM signal at the expiration of the post-atrial blanking period, and can be adjusted to a minimum sensing threshold or "sensing floor" that can be equal to the programmed atrial sensitivity.

[0115] The atrial event detector 226 may include a peak track and hold circuit or other circuit for detecting the maximum peak amplitude of the atrial EGM signal during a portion of the post-atrial blanking period. The P-wave sensing threshold starting value may be set based on the maximum peak amplitude, for example as a percentage of the maximum peak amplitude after the P-wave sensing threshold is crossed. In some examples, the P-wave sensing threshold may be set to 50% to 80% of the maximum peak amplitude. The P-wave sensing threshold may be reduced according to one or more decay rates and corresponding decay time intervals until the atrial EGM signal crosses the P-wave sensing threshold or reaches atrial sensitivity. Atrial sensitivity defines the minimum value of the atrial EGM signal amplitude that can be sensed as a P-wave. In other examples, the P-wave sensing threshold may be a fixed value that does not decay over time and may be applied as a percentage of the maximum peak amplitude of the atrial EGM signal during the post-atrial blanking period or based on a programmed atrial sensitivity. If the atrial pacing interval (which may be set to a programmed LRI) expires before the Asense signal 228 is received by the control circuit 206, the pulse generator 202 (at Figure 3 ) in some examples atrial pacing pulses can be delivered.

[0116] The ADC 252 of the ventricular sensing channel 205 can pass the rectified signal to the filter 254. The filter 254 can be a bandpass filter with a bandpass cutoff frequency for passing the R-wave signal and attenuating other cardiac event signals (e.g., P-wave and T-wave). In some examples, the high-pass and / or low-pass cutoff frequencies of the filter 254 are user programmable and / or can be adjusted by the control circuit 206 to reduce the incidence of CCOS of the P-wave by the ventricular sensing channel 205 and / or to improve the distinction between true sensed event signals and CCOS event signals, as further described below. The ventricular EGM signal 255 filtered according to different cutoff frequency settings applied by the filter 254 can be passed to the control circuit 206 for selecting the optimal bandpass cutoff frequency of the filter 254 to facilitate reliable sensing of the R-wave. In other examples, the output of the ADC 252 can be passed to the control circuit 206 for analysis to select the optimal low-pass and high-pass cutoff frequencies of the filter 254. The following is combined with Fig.10 A method for selecting high-pass and low-pass filter frequencies is described. As an example, the low-pass cutoff frequency of filter 254 may be between 25 Hz and 100 Hz or between 40 Hz and 80 Hz, and the high-pass cutoff frequency may be between 5 Hz and 25 Hz or between 15 Hz and 20 Hz. In one example, filter 224 has a low-pass frequency of 70 Hz and a high-pass frequency of 17 Hz. The bandpass cutoff frequency of filter 254 may be different from the bandpass cutoff frequency of filter 224.

[0117] The ventricular event detector 256 may include a sense amplifier, comparator, or other event detection circuit that compares the incoming rectified, filtered, and amplified ventricular EGM signal to an R-wave sensing threshold. For example, when the incoming signal crosses the R-wave sensing threshold, the ventricular event detector 256 generates a ventricular sensed event signal (Vsense) 256 that is communicated to the control circuit 206. The R-wave sensing threshold may be an automatically adjusted threshold that is automatically reduced by the sensing circuit 204. The R-wave sensing threshold amplitude is initially set to a starting value applied to the ventricular EGM signal at the expiration of the ventricular post-blanking period, and may be adjusted to a minimum sensing threshold or "sense floor" that may be equal to the programmed ventricular sensitivity.

[0118] The ventricular event detector 256 may include a peak track and hold circuit or other circuitry for detecting the maximum peak amplitude of the ventricular EGM signal after the R-wave sensing threshold is crossed during the peak tracking portion of the ventricular post-blanking period. The R-wave sensing threshold starting value may be set based on the maximum peak amplitude, for example, as a percentage of the maximum peak amplitude. In some examples, the R-wave sensing threshold may be set to 50% to 80% of the maximum peak amplitude. The R-wave sensing threshold may be reduced according to one or more decay rates and corresponding decay time intervals until the ventricular EGM signal crosses the R-wave sensing threshold or reaches the ventricular sensitivity. The ventricular sensitivity defines the smallest ventricular EGM signal amplitude that can be sensed as an R-wave. In other examples, the R-wave sensing threshold may be a fixed value that is not attenuated, for example, a fixed percentage of the maximum peak amplitude or a fixed value based on a programmed ventricular sensitivity. If the ventricular pacing interval or the AV pacing interval expires before the control circuit 206 receives the Vsense signal 258, the pulse generator 202 ( Figure 3 ) can deliver ventricular pacing pulses.

[0119] The control circuit 206 may provide sensing control signals to the sensing circuit 204. The sensing control parameters may include R-wave sensing threshold adjustment parameters, such as a percentage of the maximum peak amplitude and ventricular sensitivity for setting a starting R-wave sensing threshold, and P-wave sensing threshold adjustment parameters, such as a percentage of the maximum peak amplitude and atrial sensitivity for setting a starting P-wave sensing threshold. The sensing control parameters may include various blanking periods and refractory intervals applied to atrial EGM signals, such as a post-sensing atrial blanking period, a post-pacing atrial blanking period, an atrial refractory period, and a post-ventricular atrial blanking period. The sensing control parameters may include various blanking periods and refractory intervals applied to ventricular EGM signals, such as a post-sensing ventricular blanking period, a post-pacing ventricular blanking period, and a post-atrial ventricular blanking period.

[0120] As described above, the Asense signal 228 and the Vsense signal 258 transmitted from the sensing circuit 204 to the control circuit 206 can be used to control the timing of atrial and / or ventricular pacing pulses via the pacing timing circuit 242. When the Asense or Vsense signal is received, the pacing timing circuit 242 (e.g., Figure 3The control circuit 206 may start a pacing escape interval timer (as shown). The value reached by the escape interval timer between two consecutive Asense signals or between an Asense signal and a previous atrial pacing pulse may be determined as a PP interval (PPI) for determining the atrial rate. The value reached by the escape interval timer between two consecutive Vsense signals or between a Vsense signal and a previous ventricular pacing pulse may be determined as a RR interval (RRI) for determining the ventricular rate. The atrial rate and / or ventricular rate may be determined by the control circuit 206 for storing cardiac data in the memory 210, controlling pacing mode switching, or other pacemaker functions in some examples.

[0121] like Figure 4 As shown, when the sensing circuit 204 is configured to receive raw atrial electrical signals and raw ventricular electrical signals, in various examples, the components included in the atrial sensing channel 203 and the ventricular sensing channel 205 can be separate or shared between the two sensing channels 203 and 205. For example, pre-filters / amplifiers 220 and 250 and / or ADCs 222 and 252 can be shared by the atrial sensing channel 203 and the ventricular sensing channel 205, wherein the separated outputs are passed to the atrial event detector 226, for example, via the filter 224, and are passed to the ventricular event detector 256, for example, via the filter 254. Different filtering and amplification processes can be applied to the outputs of the ADCs before the separated signals are passed to the respective atrial event detectors 226 and ventricular event detectors 256. For example, the filter 224 can be tuned to enhance the P wave signal amplitude and attenuate other cardiac signals. The filter 254 can be tuned to enhance the R wave signal amplitude and attenuate other cardiac signals.

[0122] Furthermore, it should be understood that, in addition to Figure 4Other sensing electrode vectors other than the vectors shown in can be used to distinguish between true cardiac sensing event signals and oversensing signals according to the techniques disclosed herein. In the example of a pacemaker 14 including a tip electrode 164 and two ring electrodes 162 and 165, any combination of sensing electrode vectors, such as between electrodes 164 and 162, between electrodes 164 and 165, and / or between electrodes 162 and 165, can be received as an input to the sensing circuit 204 for distinguishing between true cardiac sensing event signals and oversensing signals according to the techniques disclosed herein. As described below, the control circuit 206 can be configured to determine a quantitative relationship between a feature of the ventricular EGM signal and a similar feature of the atrial EGM signal. In the illustrative example presented herein, the quantitative relationship is determined as the ratio of a feature of the ventricular EGM signal to a similar feature of the atrial EGM signal, and is referred to as a "sensing ratio". The quantitative relationship can be used to distinguish between CCOS events sensed by the sensing channel 203 or 205 and true events. The quantitative relationship can be determined by dividing, multiplying, adding and / or subtracting a feature of the ventricular EGM signal and a similar feature of the atrial EGM signal. In various examples, the quantitative relationship can be a "sensing ratio", "sensing product", "sensing difference" or "sensing sum" determined by dividing, multiplying, subtracting or adding the ventricular EGM signal feature and the atrial EGM signal feature, respectively. In some examples, a weighting factor can be used to determine the quantitative relationship. The quantitative relationship can be determined as any combination of dividing, multiplying, subtracting and / or adding the values ​​of the ventricular EGM signal feature and the atrial EGM signal feature. The EGM signal transmitted to the atrial event detector 226 and the EGM signal used to determine the signal feature corresponding to the P wave sensed by the atrial event detector 226 and used to calculate the quantitative relationship (e.g., a sensing ratio or any of the examples listed above) can be the same or two different sensing electrode vectors. The EGM signal transmitted to the ventricular event detector 256 and the EGM signal used to determine the signal characteristics corresponding to the R wave sensed by the ventricular event detector 256 for calculating a quantitative relationship (e.g., a sensing ratio) can be sensed using the same or two different sensing electrode vectors. Therefore, the sensing circuit included in a medical device configured to operate according to the presently disclosed technology includes one or more sensing circuits, which can be configured as multiple sensing channels, having separate or shared components for filtering, amplifying, digitizing and / or rectifying two or more raw cardiac electrical signals for sensing P wave sensing threshold crossings, sensing R wave sensing threshold crossings, determining atrial EGM signal characteristics associated with the Asense signal 228, and determining ventricular EGM signal characteristics associated with the Vsense signal 258.The sensing circuitry and control circuitry 206 may individually or cooperatively determine one or more signal characteristics corresponding to the time of a P-wave sensing threshold crossing and determine one or more signal characteristics corresponding to the time of an R-wave sensing threshold crossing.

[0123] Figure 5 300 is a flow chart of a method that may be performed by the pacemaker 14 for confirming a sensed cardiac event signal and identifying a CCOS event signal. At block 302, the control circuit 206 receives a first signal corresponding to a cardiac event signal. Figure 4 , the first signal may be a sense event signal (Asense signal or Vsense signal) from the sensing circuit 204 indicating the time of a P wave sensing threshold crossing or an R wave sensing threshold crossing, respectively. In other examples, the processing circuitry (e.g., the processor 244) of the control circuit 206 may be configured to receive the atrial EGM signal 225 and the ventricular EGM signal 255 from the sensing circuit 204 (see Figure 4 ). The control circuit 206 may receive a first sensed event signal by receiving an EGM signal and identifying a cardiac event (e.g., a P wave or an R wave) from a corresponding atrial EGM signal or a ventricular EGM signal. A cardiac event may be identified from a corresponding EGM signal based on the amplitude, slope, morphology, or other characteristics of the cardiac waveform.

[0124] In response to receiving the first sensed event signal at box 302, the control circuit 206 may start a confirmation delay at box 304. The confirmation delay is a time interval that can be started by the control circuit 206, for example, by starting a timer in the processor 244. The confirmation delay can be set to 10 milliseconds (ms), 20ms, 30ms, 50ms, 70ms, 100ms, or other time intervals. The confirmation delay may be programmable by the user. The confirmation delay may be rate adaptive so that it can be adjusted to a shorter delay as the heart rate increases and to a longer delay as the heart rate decreases. The heart rate may be determined by the control circuit 206 based on the mean, median, or other representative value of the most recent specified number of PPIs or RRIs (e.g., the most recent 8 to 20 PPIs determined between confirmed Asense signals and / or atrial pacing pulses, or the most recent 8 to 20 RRIs determined between confirmed Vsense signals and / or ventricular pacing pulses).

[0125] The first sensed event signal may be a "real" cardiac event sensed from an expected cardiac chamber (atrial chamber or ventricular chamber), or a CCOS event occurring in another cardiac chamber (ventricle or atrium) sensed by one sensing channel of the sensing circuit 204. For example, if the first sensed event signal is an Asense signal received from the atrial sensing channel 203, the first sensed event signal may be a CCOS far-field R-wave that is subsequently sensed as a real R-wave by the ventricular sensing channel 205 within 10ms to 100ms after the far-field R-wave crosses the P-wave sensing threshold of the atrial sensing channel 203. In other cases, if the first sensed event signal is an Asense signal received from the atrial sensing channel 203, the first sensed event signal may be a real P-wave that is subsequently over-sensed as a false R-wave by the ventricular sensing channel 205, resulting in a false Vsense signal within 10ms to 100ms after the Asense signal.

[0126] In other cases, the first sensed event signal received at block 302 may be a Vsense signal. The Vsense signal may be a true Vsense signal, but may be followed by a false Asense signal within a confirmation delay due to CCOS of the far-field R wave by the atrial sensing channel 203. The Vsense signal may be a false Vsense signal due to oversensing of a large P wave that may subsequently be sensed by the atrial sensing channel 203.

[0127] The confirmation delay initiated at block 304 may be a fixed delay regardless of whether the Asense event signal is received first at block 302 or the Vsense event signal is received first at block 302. In other examples, when the first sensed event signal received at block 302 is an Asense event signal, the confirmation delay may be set differently than when the first sensed event signal received at block 302 is a Vsense event signal, for example, set shorter or longer. Depending on filtering, amplification, P-wave and R-wave sensing thresholds, and other factors, the maximum time interval for which a CCOS event is expected to occur on one sensing channel relative to an actual sensed event on another sensing channel may be different.

[0128] The control circuit 206 may determine at block 306 whether the second sensed event signal is received before the confirmation delay expires (as determined at block 308). If the second sensed event signal is not received before the confirmation delay expires ("yes" branch of block 308), the control circuit 206 may confirm the first sensed event signal as a true sensed event at block 314. If the first sensed event signal corresponds to a sensed P wave, the sensed P wave is confirmed as a true event at block 314. If the first sensed event signal corresponds to a sensed R wave, the sensed R wave may be confirmed at block 314.

[0129] At box 318, the control circuit 206 may perform a pacing and / or sensing response to the confirmed sensed event signal. If the confirmed event is a P wave, the control circuit 206 may initiate, for example, an AV pacing interval, an atrial LRI, a post-sensing atrial blanking period, an atrial refractory period, and a post-atrial ventricular blanking period. A pending atrial pacing pulse (e.g., scheduled at the expiration of an atrial LRI that is running when the first sensed event signal is received at box 302) may be suppressed and the atrial LRI may be restarted. When the confirmed event is a P wave, a ventricular pacing escape interval that is running at the expiration of the confirmation delay may continue to run. If the ventricular pacing escape interval expires during the confirmation delay, a pending ventricular pacing pulse may be delivered at the expiration of the confirmation delay when the confirmed event is a P wave. In other examples, the control circuit 206 may additionally or alternatively control the telemetry circuit 208 to transmit an atrial event communication signal when the confirmed event is a P wave. The atrial event signal can be received by another medical device (e.g., an intracardiac leadless ventricular pacemaker), which is triggered to deliver ventricular pacing pulses in response to receiving the transmitted atrial event signal.

[0130] If the confirmed event at box 314 is an R wave, the control circuit 206 can initiate various pacing timing and / or sensing control intervals, such as, for example, a ventricular LRI (which can be set as a temporary rate response or rate smoothing interval), a post-sensing ventricular blanking period, a ventricular refractory period, a post-ventricular atrial blanking period, and a post-ventricular atrial refractory period. If the confirmed event is an R wave, the control circuit 206 can suppress pending ventricular pacing pulses that were scheduled to be delivered at the expiration of the AV pacing interval and / or ventricular pacing interval that was running when the first sensed event signal was received at box 302. The ventricular pacing interval can be restarted in response to confirming that the first event is a true R wave. When the confirmed event is an R wave, the atrial pacing escape interval that was running at the expiration of the confirmation delay can continue to run. If the atrial pacing escape interval expires during the confirmation delay, when the confirmed event is an R wave, a pending atrial pacing pulse can be delivered at the expiration of the confirmation delay. In other examples, the control circuit 206 may additionally or alternatively control the telemetry circuit 208 to transmit a ventricular event communication signal when the confirmed event is an R wave. The transmitted ventricular event communication signal may be received by another medical device (e.g., an intracardiac leadless atrial pacemaker, an ICD, or other medical device), which may use the received ventricular event communication signal to determine the cardiac rhythm, e.g., for arrhythmia detection and / or for controlling the delivered electrical stimulation therapy.

[0131] When a second sensed event signal is received by the control circuit 206 at block 306 (“yes” branch of block 308) before the delay is confirmed to have expired at block 306, the control circuit 206 may determine a quantitative relationship between the characteristics of the atrial EGM signal 225 received from the atrial sensing channel and the characteristics of the ventricular EGM signal 255 received from the ventricular sensing channel 205 (see Figure 4 ). In the example shown, the control circuit 206 determines a sensing ratio at box 310. The sensing ratio can be determined as a ratio of a feature determined from the atrial EGM signal 225 to a feature determined from the ventricular EGM signal 255. In some examples, the ratio is a ratio of the maximum peak amplitudes of the respective signals. The maximum peak amplitude can be determined based on the atrial EGM signal and the ventricular EGM signal after the sensing event signal received at box 302 (e.g., within a confirmation delay). In other examples, the maximum peak amplitude can be determined based on the respective EGM during the post-sensing blanking period (or its peak tracking portion) applied by the respective sensing channel. As described above, the atrial event detector 226 and the ventricular event detector 256 can each include a peak tracking and holding circuit or other components that determine the maximum peak amplitudes of the respective atrial EGM signal and the ventricular EGM signal after the respective P-wave sensing threshold crossing and the R-wave sensing threshold crossing. The sensing circuit 204 can be configured to output the maximum peak amplitude of the atrial EGM after the P-wave sensing threshold crossing to the control circuit 206. The sensing circuit 204 may be configured to output a ventricular EGM maximum peak amplitude after the R-wave sensing threshold is crossed to the control circuit 206. In other examples, the control circuit 206 may be configured to determine a maximum peak amplitude of a corresponding atrial EGM signal 225 or ventricular EGM signal 255 received from the sensing circuit 204 after an Asense or Vsense signal or in response to identifying a P wave or R wave from the corresponding EGM signal.

[0132] In other examples, the sensing ratio can be a ratio of different features of the EGM signal. For example, the sensing ratio can be a ratio of the maximum slope, signal width, signal area, or other features of the atrial EGM signal and the ventricular EGM signal determined based on each corresponding EGM signal after the first sensing event signal and / or the second sensing event signal. In some other examples, the control circuit 206 can determine more than one sensing ratio of more than one feature of the atrial and ventricular EGM signals. For example, the ratio of the maximum peak amplitude and the ratio of the maximum peak slope can be determined as the sensing ratio at box 310.

[0133] For the purpose of illustration, the quantitative relationship is described as a sensing ratio of the maximum peak amplitude in the examples given in conjunction with the accompanying drawings. However, it should be understood that in other examples, instead of determining the quantitative relationship as a ratio between the characteristics of the atrial EGM signal and the characteristics of the ventricular EGM signal, the quantitative relationship can be determined as the difference between the atrial EGM signal characteristics and the simulated ventricular EGM signal characteristics. The quantitative relationship can be determined as the maximum peak difference, the maximum slope difference, the signal width difference, the signal area difference, or the difference between another characteristic of the atrial and ventricular EGM signals. In some other examples, the quantitative relationship can be determined as a sum, for example, the maximum peak sum, the maximum slope sum, the signal width sum, the signal area sum, or the sum of another characteristic of each of the atrial and ventricular EGM signals. In other examples, the quantitative relationship can be determined as a product, for example, the maximum peak product, the maximum slope product, the signal width product, the signal area product, or the product of another characteristic of each of the atrial and ventricular EGM signals. In some examples, the quantitative relationship can be a standardized ratio, standardized product, standardized difference, or standardized sum between the atrial EGM signal characteristics and the ventricular EGM signal characteristics, which is achieved by normalizing the quantitative relationship with a selected reference value. The quantitative relationship can be determined by the control circuit 206 for performing a comparative analysis of two signals sensed by the sensing circuit 204 within the confirmation delay to distinguish between a true sensing event (expected to be sensed) and a CCOS event (expected not to be sensed by a given sensing channel). The quantitative relationship can be determined by the control circuit 206 for performing a comparative analysis between the quantitative relationship and a distinction threshold applied to the quantitative relationship, which distinguishes the relative size of the quantitative relationship when the first event is a true event (expected to be sensed) and when the first event is a CCOS event (expected not to be sensed by a given sensing channel).

[0134] At box 312, the control circuit 206 may compare the sensing ratio with a threshold value defined for confirming the first sensing event signal. In one example, the sensing ratio is determined as a ratio of maximum peak amplitudes. The sensing ratio can be determined as a ratio of the maximum peak amplitude of the ventricular EGM signal determined after the Vsense signal (which can be the first sensing event signal or the second sensing event signal received by the control circuit 206) and the maximum peak amplitude of the atrial EGM signal determined after the Asense signal (which can be the second sensing event signal or the first sensing event signal received by the control circuit 206).

[0135] The sensing ratio determined as the ratio of the maximum amplitude of the ventricular EGM signal to the maximum amplitude of the atrial EGM signal may be referred to as the V / A sensing ratio. For illustration, the example described below refers to the V / A sensing ratio as the sensing ratio for confirming the sensed event signal. However, it should be understood that the sensing ratio may be additionally or alternatively determined as the A / V ratio of the maximum peak amplitude of the atrial EGM signal to the maximum peak amplitude of the ventricular EGM signal. In addition, the V / A sensing ratio and / or the A / V sensing ratio may be determined for other EGM signal features as described above, such as slope, signal width, signal area, etc. It is further contemplated that the sensing ratio may be determined as a V / A sensing ratio or an A / V sensing ratio, depending on which sensing event signal (Asense or Vsense) is received first and which sensing event signal (Vsense or Asense) is received subsequently within the confirmation delay. When determining both the V / A ratio and the A / V sensing ratio, the V / A sensing ratio and the A / V sensing ratio may be determined using the same characteristic of the corresponding atrial EGM signal and the ventricular EGM signal (e.g., maximum peak amplitude). In other examples, the V / A sensing ratio may be determined using one characteristic of the corresponding atrial and ventricular EGM signals (e.g., maximum amplitude), and the A / V sensing ratio may be determined using different characteristics thereof (e.g., maximum slope). Thus, while the examples presented herein relate to V / A sensing ratios determined as ratios of maximum amplitudes that may be compared to a P-wave confirmation threshold and / or an R-wave confirmation threshold, it should be understood that one or more V / A sensing ratios and / or one or more A / V ratios may be determined as ratios of amplitudes and / or other EGM signal characteristics for comparison to corresponding P-wave confirmation thresholds and / or R-wave confirmation thresholds.

[0136] If the first sensed event signal is an Asense signal, the control circuit 206 may compare the V / A sensing ratio to the P wave confirmation threshold at box 312. The V / A sensing ratio may be determined as the ratio of the maximum peak amplitude of the ventricular EGM (or a subsequent Vsense signal occurring within the confirmation delay) after the P wave sensing threshold is crossed to the maximum peak amplitude of the atrial EGM after the same P wave sensing threshold is crossed. If the Asense signal is true and the Vsense signal received within the confirmation delay is a CCOS P wave, the V / A sensing ratio is expected to be relatively low. If the Asense signal is false, the V / A sensing ratio is expected to be a relatively high value due to the large R wave peak amplitude in the ventricular EGM signal and the relatively small amplitude of the far-field R wave that is incorrectly over-sensed as a P wave in the filtered atrial EGM signal. When the V / A sensing ratio is less than (or equal to) the P wave confirmation threshold at box 312, the control circuit 206 may confirm the Asense signal received at box 302 as a true P wave at box 314. In other examples, the maximum ventricular EGM signal amplitude may be required to be less than the R-wave threshold amplitude, and the maximum atrial EGM signal amplitude may be required to be greater than the P-wave threshold amplitude so that the control circuit 206 confirms the Asense signal as a true P wave at box 314 when the V / A sensing ratio is less than the P-wave confirmation threshold.

[0137] When the V / A sense ratio is greater than the P-wave confirmation threshold at box 312, the Vsense signal received at box 306 may correspond to a true R-wave, where the previous Asense signal (first received at box 302) corresponds to a CCOS far-field R-wave. At box 316, the control circuit 206 may confirm that the second event signal received as the Vsense signal is a true R-wave. In other examples, the maximum ventricular EGM signal amplitude may be required to be greater than the R-wave threshold amplitude, and the maximum atrial EGM signal amplitude may be required to be less than the P-wave threshold amplitude in order for the control circuit 206 to confirm that the Vsense signal is a true R-wave at box 316.

[0138] If the first sensed event signal received at block 302 is a Vsense signal, the control circuit 206 may compare the V / A sense ratio to the R-wave confirmation threshold at block 312. If the Vsense signal is true and the Asense signal received within the confirmation delay is a CCOS far-field R-wave, the V / A sense ratio, determined as the ratio of the maximum peak amplitude of the ventricular EGM after an R-wave sense threshold crossing to the maximum peak amplitude of the atrial EGM after the same R-wave sense threshold crossing (or a subsequent P-wave sense threshold crossing occurring within the confirmation delay), is expected to be relatively high. If the V / A sense ratio is greater than the R-wave confirmation threshold at block 312, the control circuit 206 may confirm at block 314 that the Vsense signal received at block 302 is a true R-wave.

[0139] When the V / A sensing ratio is less than (or equal to) the R-wave confirmation threshold at block 312, the Vsense signal may correspond to a CCOS P-wave, wherein a subsequent Asense signal occurring within the confirmation delay time corresponds to a true P-wave. When the V / A sensing ratio is less than (or equal to) the R-wave confirmation threshold and the Vsense signal is received before the Asense signal, the control circuit 206 may confirm the second event signal (received as the Asense signal) as a true P-wave at block 316. The P-wave confirmation threshold and the R-wave confirmation threshold applied to the V / A sensing ratio may be the same or different from each other.

[0140] When a true P wave occurs, the V / A sensing ratio may be typically less than 1.0 or less than 1.25, as an example. When a true R wave occurs, the V / A sensing ratio may be typically greater than 1.5, greater than 2.0, in the range of 2.0 to 5.0, or as an example, may be as high as 10 or 15. Thus, the P wave confirmation threshold may be equal to or between 1.0 and 1.5, and may be 1.25 in one example. The R wave confirmation threshold may be set equal to the P wave confirmation threshold. In other examples, the R wave confirmation threshold may be higher, such as 1.5 to 2.0 or higher.

[0141] As below combined Fig. 9 As described above, when a reliable Asense signal is received and when a reliable Vsense signal is received, a threshold ratio for confirming P waves and R waves can be established by the control circuit 206 based on the analysis of the atrial EGM signal and the ventricular EGM signal. After confirming that the first event or the second event is a true sensed event, the control circuit 206 can perform a pacing and / or sensing response at block 318 as described above.

[0142] Figure 6 4 is a timing diagram 400 of an atrial (A) EGM signal 402, a ventricular (V) EGM signal 422, and a sensed event marker channel 440, depicting a cardiac sensed event signal that may be received by the control circuit 206 and confirmed as a true event or identified as a CCOS event by the control circuit 206 according to some examples. The atrial sensing channel 203 may apply a P wave sensing threshold 404 to the atrial EGM signal 402 to sense an atrial event. The atrial sensing channel 203 may generate an Asense signal 442 in response to a P wave sensing threshold crossing 406. Although the P wave sensing threshold is within Figure 6 , which may correspond to atrial sensitivity, but it should be understood that the P-wave sensing threshold 404 may be a threshold that is automatically adjusted from a starting amplitude that may be reduced to a minimum sensing threshold or until a P-wave sensing threshold crossing occurs.

[0143] In response to receiving the Asense event signal 442, the control circuit 206 can initiate the confirmation delay 408. The ventricular sensing channel 205 can apply the R-wave sensing threshold 424 to the ventricular EGM signal 422. The ventricular sensing channel 205 can generate a Vsense signal 444 in response to the R-wave sensing threshold crossing 426. The R-wave sensing threshold 424 is shown as a fixed amplitude threshold, for example, equal to the programmed ventricular sensitivity. However, it should be understood that the R-wave sensing threshold 424 can be an automatically adjusted threshold that decreases from the starting amplitude downward to the minimum sensing threshold or until the R-wave sensing threshold crossing occurs.

[0144] Because the Vsense signal 444 occurs before the confirmation delay 408 expires, the control circuit 206 can determine the V / A sense ratio as the ratio of the ventricular EGM maximum peak amplitude 432 to the atrial EGM maximum peak amplitude 412. The ventricular EGM maximum peak amplitude 432 can be determined during the confirmation delay 408 or within a sensing time interval (e.g., within 20 ms to 100 ms) after the R-wave sensing threshold crossing 426. The atrial EGM maximum peak amplitude 412 can be determined as the maximum peak amplitude during the confirmation delay 408 or within a sensing time interval after the P-wave sensing threshold crossing 406. The quantitative relationship between the atrial EGM signal characteristics and the ventricular EGM signal characteristics can alternatively be determined as the difference, sum, or product indicated above, or any combination thereof.

[0145] The V / A sensing ratio (or other quantitative relationship) may be compared to the P wave confirmation threshold by the control circuit 206 because the Asense event signal 442 is received first and the Vsense event signal 444 is received subsequently. When the atrial EGM maximum peak amplitude 412 of the true P wave 430 is relatively high and the ventricular EGM maximum peak amplitude 432 of the CCOS P wave 410 is relatively low, the V / A sensing ratio may be less than the P wave confirmation threshold. In response to the V / A sensing ratio being less than the P wave confirmation threshold, the control circuit 206 may confirm that the Asense event signal 442 is a true P wave. The control circuit 206 may identify the Vsense event signal 444 as a CCOS event signal. In other examples, the V / A sensing ratio (or other quantitative relationship) may be additionally or alternatively compared to the R wave confirmation threshold. If the V / A sensing ratio is less than the R wave confirmation threshold, the control circuit 206 may confirm that the Asense event signal 442 is a true P wave and identify the Vsense event signal 444 as a CCOS signal. As described above, the control circuit 206 can provide pacing and / or sensing responses based on the confirmed P wave.

[0146] The ventricular sensing channel 205 may generate another Vsense event signal 446 in response to the R wave sensing threshold crossing 434. The control circuit 206 may initiate a confirmation delay 428 in response to receiving the Vsense event signal 446. In response to the atrial event sensing threshold crossing 414 of the atrial EGM signal 402, the Asense event signal 448 is received by the control circuit 206 before the confirmation delay 428 expires. Because the second sensed cardiac event signal is received during the confirmation delay 428, the control circuit 206 determines the V / A sensing ratio. The control circuit 206 may determine the V / A sensing ratio as the ratio of the ventricular EGM maximum peak amplitude 438 to the atrial EGM maximum peak amplitude 418. The maximum peak amplitudes 418 and 438 may be determined based on the respective atrial and ventricular EGM signals sensed during the confirmation delay 428 or within a post-sensing time interval (e.g., up to 100 ms after the respective sensing threshold crossing 414 or 434).

[0147] The control circuit 206 may compare the V / A sensing ratio (or other quantitative relationship) to the R-wave confirmation threshold because the Vsense event signal 446 is the first sensing event signal outside the confirmation delay and the Asense event signal 448 is received within the confirmation delay 428. In this case, the ratio of the maximum peak amplitude 438 of the true R-wave 436 in the atrial EGM signal 402 to the maximum peak amplitude 418 of the far-field R-wave 416 is relatively high. The control circuit 206 may confirm that the Vsense event signal 446 corresponds to the true R-wave 436 in response to the V / A sensing ratio being greater than the R-wave confirmation threshold. The Asense signal 448 may be identified as a CCOS event signal corresponding to an over-sensed far-field R-wave 416 on the atrial sensing channel 203. In some examples, the control circuit 206 may additionally or alternatively compare the V / A sensing ratio (or other quantitative relationship) to the P-wave confirmation threshold. When the V / A sense ratio is greater than the P wave confirmation threshold and / or the V / A sense ratio is greater than the R wave confirmation threshold, the Vsense event signal 446 is confirmed as a true sensed R wave. The control circuit 206 can perform one or more pacing control and / or sensing control responses to the confirmation of the sensed R wave.

[0148] In other examples, the control circuit 206 may compare the V / A sensing ratio to a previously established P wave confirmation threshold and an R wave confirmation threshold. The control circuit 206 may determine which of the P wave confirmation threshold and the R wave confirmation threshold the V / A sensing ratio (or other quantitative relationship) is closest to. When the V / A sensing ratio is closest to the P wave confirmation threshold, the control circuit 206 may confirm a true P wave. When the V / A sensing ratio is closest to the R wave confirmation threshold, the control circuit 206 may confirm a true R wave.

[0149] In other examples, the control circuit 206 may determine the quantitative relationship as the difference between the ventricular EGM maximum peak amplitude and the atrial EGM maximum peak amplitude. The difference may be determined as an absolute value, or may be determined as a positive or negative value. The difference may be determined as the ventricular EGM maximum peak amplitude 438 minus the atrial EGM maximum peak amplitude 418, or the atrial EGM maximum peak amplitude 418 minus the ventricular EGM maximum peak amplitude 438. The difference may be compared to an R-wave confirmation threshold and / or a P-wave confirmation threshold. For example, when the difference is determined as the ventricular EGM maximum peak amplitude minus the atrial EGM maximum peak amplitude, if the difference is greater than the R-wave confirmation threshold or closer to the R-wave confirmation threshold, the R-wave may be confirmed. If the difference is less than the P-wave confirmation threshold or closer to the P-wave confirmation threshold, the P-wave may be confirmed. In yet other examples, the quantitative relationship may be determined as the sum or product of the ventricular EGM maximum peak amplitude and the atrial EGM maximum peak amplitude. The sum or product may be compared to a corresponding R-wave confirmation threshold and / or a P-wave confirmation threshold.

[0150] Figure 7 5 is a conceptual diagram 500 illustrating sensing operating states of a pacemaker 14 according to some examples. In block 502, the control circuit 206 may be in a pending state waiting to receive a cardiac event signal. As described above, the control circuit 206 may receive an Asense event signal or a Vsense event signal from the sensing circuit 204. In other examples, the control circuit 206 may receive a cardiac event signal by receiving an atrial EGM signal and detecting an atrial event signal from the atrial EGM signal, for example, based on a P-wave sensing threshold, waveform morphology, or other criteria, or by receiving a ventricular EGM signal and detecting a ventricular event signal from the ventricular EGM signal, for example, based on an R-wave sensing threshold, waveform morphology, or other criteria. For purposes of illustration, in the description of the sensing state diagram 500 and other flow charts presented herein, the control circuit 206 is described as receiving an atrial event signal as an Asense signal and a ventricular event signal as a Vsense signal from the corresponding atrial and ventricular sensing channels of the sensing circuit 204.

[0151] In response to receiving a Vsense signal outside the confirmation delay, the control circuit 206 may transition from the pending wait state 502 to the pending Vsense state 504 and start the confirmation delay. The control circuit 206 may transition from the pending Vsense state 504 to the confirmed Vsense state 506 (center arrow 516) in response to the confirmation delay expiring without an Asense event signal. In other cases, when the V / A sensing ratio (or another quantitative relationship, such as VA difference or VA sum or VA product) is greater than the R wave confirmation threshold (left arrow 514), the control circuit 206 may transition from the pending Vsense state 504 to the confirmed Vsense state 506 in response to receiving an Asense event signal before the confirmation delay expires. The control circuit 206 may transition from the pending Vsense state 504 to the confirmed Asense state 507 in response to receiving an Asense event signal before the confirmation delay expires and the V / A sensing ratio (or other quantitative relationship) is less than the R wave confirmation threshold (right arrow 518).

[0152] exist Figure 7 In the example, the transition to the Vsense state 506 occurs in response to the V / A sensing ratio being equal to the R-wave confirmation threshold (when Asense follows Vsense) or being equal to the P-wave threshold (when Vsense follows Asense). It should be understood that in other examples, the transition to the Asense state 507 may occur in response to the V / A sensing ratio being equal to the R-wave confirmation threshold or being equal to the P-wave confirmation threshold. The response to the V / A sensing ratio being equal to one of the P-wave confirmation threshold or the R-wave confirmation threshold may depend on the value selected or programmed as the P-wave confirmation threshold or the R-wave confirmation threshold.

[0153] In response to transitioning to the asserted Vsense state 506, the control circuit 206 may apply the post-ventricular blanking period and transition back to the wait state 502. For example, the control circuit 206 may pass the asserted Vsense signal back to the sensing circuit 204. The ventricular sensing channel 205 may apply the post-sensing ventricular blanking period to the ventricular EGM signal starting from the time of the Vsense event signal. The atrial sensing channel 203 may apply the post-ventricular atrial blanking period to the atrial EGM signal starting from the time of the Vsense event signal.

[0154] When the control circuit 206 receives an Asense event signal during the waiting state 502, the control circuit 206 may transition to the pending Asense state 505. The control circuit 206 may initiate a confirmation delay. The control circuit 206 may transition to the confirmed Asense state 507 in response to the expiration of the confirmation delay and the lack of a Vsense signal (center arrow 517) or in response to receiving a Vsense signal during the confirmation delay and the V / A sensing ratio (or another quantitative relationship, such as a VA difference, a VA sum, or a VA product) being less than (or equal to) a P-wave confirmation threshold (right arrow 515). The control circuit 206 may transition from the pending Asense state 505 to the confirmed Vsense state 506 in response to receiving a Vsense signal during the confirmation delay and the V / A sensing ratio (or other quantitative relationship) being greater than the P-wave confirmation threshold (left arrow 519).

[0155] In response to the transition to the confirmed Asense state 507, the control circuit 206 can apply the post-atrial blanking period and transition back to the wait state 502. For example, the control circuit 206 can pass the confirmed Asense signal back to the sensing circuit 204. The atrial sensing channel 203 can apply the post-sensing atrial blanking period to the atrial EGM signal starting from the time of the Asense event signal. The ventricular sensing channel 205 can apply the post-atrial ventricular blanking period to the ventricular EGM signal starting from the time of the Asense event signal. The blanking period applied in response to the confirmed Vsense signal or the confirmed Asense signal causes the sensing circuit 204 to ignore or discard any sensing threshold crossing that may occur in the atrial or ventricular EGM signal during the blanking period applied to the corresponding signal.

[0156] In addition to applying blanking periods based on confirmed cardiac event signals, the control circuit 206 can also initiate pacing intervals based on the current pacing mode and the confirmed cardiac event signal. In response to transitioning to the confirmed Asense state 507, the control circuit 206 can initiate AV pacing intervals (during the atrial synchronous ventricular pacing mode) and / or atrial pacing intervals, such as atrial LRI or rate-responsive pacing intervals (during the single-chamber atrial pacing mode or during the dual-chamber pacing mode). When transitioning to the Asense state 507, scheduled pending atrial pacing pulses can be suppressed.

[0157] In response to the transition to the confirmed Vsense state 506, the control circuit 206 can initiate a ventricular pacing interval. When transitioning to the Vsense state 506, the scheduled pending ventricular pacing pulse can be suppressed. One or more pacing intervals initiated in response to the confirmed Vsense or Asense event signal can have an effective start time at the moment of the received Vsense or Asense event signal, respectively. In other examples, any delay in the scheduled pacing pulse due to the confirmation delay and processing time of transitioning from the pending Vsense state 504 or Asense state 505 to the confirmed state 506 or 507 can be considered negligible, or the pacing interval can be adjusted by the pacing timing circuit 242 to account for the confirmation delay and processing time. In various examples, any blanking period, refractory period, pacing escape interval, or other timing interval initiated by the control circuit 206 in response to the confirmed cardiac event signal can be adjusted to have an effective start time corresponding to the time of the received Asense or Vsense event signal as the confirmed cardiac event signal.

[0158] In some examples, the confirmation delay is a programmable value, which can be a single value that is initiated as a time interval in response to an Asense event signal or a Vsense event signal (whichever is received first). As previously described herein, in other examples, the confirmation delay may be a first confirmation delay or a second confirmation delay different from the first confirmation delay, depending on whether the Asense event signal is received first or the Vsense event signal is received first. The control circuit 206 may initiate a longer or shorter confirmation delay in response to the Asense event signal compared to the confirmation delay initiated by the control circuit 206 in response to the Vsense event signal. It should also be noted that in some examples, the confirmation delay may be programmed to 0ms by a clinician or other user. In some patients, CCOS may not occur (or may rarely occur), and the application of the confirmation delay is not necessary. When the confirmation delay is programmed to 0ms, the Asense event signal and the Vsense event signal received by the control circuit 206 are respectively responded to as true confirmed Asense event signals and Vsense event signals, for controlling the sensing and / or pacing response to the received cardiac sensing event signal.

[0159] Figure 8600 is a diagram of an atrial EGM signal 602 and a ventricular EGM signal 622 that can be sensed by the sensing circuit 204. Each of the atrial EGM signal 602 and the ventricular EGM signal 604 can be a filtered, amplified, and rectified EGM signal that can be transmitted to the atrial event detector 226 or the ventricular event detector 256, respectively, and / or transmitted to the control circuit 206 for identification of a corresponding P wave signal or R wave signal. The rectified atrial EGM signal 602 includes a true P wave 601 and a far-field R wave 615. The rectified ventricular EGM signal 622 includes a true R wave 625 and a cross-channel P wave 621.

[0160] The atrial sensing channel 203 may generate an Asense event signal 608 in response to the atrial EGM signal 602 crossing the P wave sensing threshold 604 at the threshold crossing 606. The control circuit 206 may initiate a confirmation delay 610 (when the confirmation delay is not already in progress) in response to receiving the Asense event signal 608. In this example, no cross-chamber P wave 621 is sensed during the confirmation delay 610, and a subsequent R wave 625 is sensed after the confirmation delay 610 expires. Therefore, the control circuit 206 may confirm that the Asense event signal 608 is a true sensed P wave.

[0161] In some examples, when a P wave is confirmed without a Vsense event signal based on expiration of confirmation delay 610, control circuit 206 can determine a V / A sense ratio (or other quantitative relationship) that represents a true P wave when no cross-cavity oversensing is occurring. Although described with reference to a quantitative relationship as a V / A sense ratio Figure 8 , but it will be appreciated that the combined analysis may be performed using quantitative relationships (e.g., differences, sums, or products) of ventricular and atrial EGM signal characteristics other than the sensed ratios described herein. Figure 8 (and other flowcharts and figures presented herein). The atrial EGM maximum peak amplitude 612 and the ventricular EGM maximum peak amplitude 634 following an Asense event signal 608 may be determined. The maximum peak amplitudes 612 and 634 may be determined based on the corresponding atrial EGM signal 602 and the ventricular EGM signal 622 sensed during the confirmation delay 610 or during a longer post-sensing time interval (e.g., within 20ms to 100ms after the Asense event signal 608). The V / A sensing ratio (or other quantitative relationship) determined based on the peak amplitudes 612 and 634 when a P wave is confirmed in the absence of a CCOS event may be stored in the memory 210 and / or used by the control circuit 206 to establish or update a P wave confirmation threshold applied to the V / A sensing ratio (or other quantitative relationship) determined when a pending Asense event signal is followed by a Vsense event signal within the confirmation delay during future cardiac cycles.

[0162] In some examples, a V / A sensing ratio determined as the ratio of the ventricular EGM maximum peak amplitude 634 to the atrial EGM maximum peak amplitude 612 is cached in a memory along with a plurality of V / A sensing ratios determined when an Asense event signal is confirmed based on expiration of a confirmation delay without a Vsense event signal. The P wave confirmation threshold may be determined as a representative value of a plurality of cached V / A sensing ratios, such as a mean, median, trimmed mean, trimmed median, maximum, or other representative value. In other examples, the control circuit 206 may use a single V / A sensing ratio to update or establish the P wave confirmation threshold. In conjunction with Fig. 9 Exemplary techniques for establishing or updating a P-wave confirmation threshold applied to a V / A sensing ratio are described.

[0163] In response to asserting the Asense event signal 608, the sensing circuit 204 may apply a post-sensing atrial blanking period 616 to the atrial EGM signal 602. The post-sensing atrial blanking period 616 may have an effective start time at the time of the Asense event signal 608. Any P-wave sensing threshold crossing during the post-sensing atrial blanking period 616 is not sensed as a P wave, does not result in another Asense event signal being generated by the atrial sensing channel 203, or is ignored by the control circuit 206 when controlling atrial and ventricular pacing.

[0164] In response to asserting the Asense event signal 608, the sensing circuit 204 may apply a post-atrial ventricular blanking period 618 to the ventricular EGM signal 622. The post-atrial ventricular blanking period 618 may have an effective start time at the time of the Asense event signal 608. Any subsequent R-wave sensing threshold crossings during the post-atrial ventricular blanking period 618 are not sensed as R waves, do not result in the generation of a Vsense event signal by the ventricular sensing channel 205, or are ignored by the control circuit 206 when controlling ventricular pacing. Figure 8 As shown, the post-atrial blanking period 616 and the post-atrial ventricular blanking period 618 may be longer than the confirmation delay 610 , but are not necessarily longer than the confirmation delay 610 .

[0165] The ventricular sensing channel 205 may generate a Vsense event signal 628 in response to the ventricular EGM signal 622 crossing the R-wave sensing threshold 624 at the threshold crossing 626. The control circuit 206 may initiate a confirmation delay 630 (if a confirmation delay is not already in progress) in response to receiving the Vsense event signal 628. In this example, the far-field R-wave 615 in the atrial EGM signal 602 is not sensed by the atrial sensing circuit 203 during the confirmation delay 630. Therefore, the control circuit 206 may confirm that the Vsense event signal 628 is a true sensed R-wave when the confirmation delay 630 expires.

[0166] In some examples, when an R wave is confirmed without an Asense event signal based on the expiration of the confirmation delay 630, the control circuit 206 can determine a V / A sense ratio (or other quantitative relationship) that represents a true R wave when no cross-chamber oversensing is occurring. The atrial EGM maximum peak amplitude 614 and the ventricular EGM maximum peak amplitude 632 after the Vsense event signal 628 can be determined. The maximum peak amplitudes 614 and 632 can be determined based on the corresponding atrial EGM signal 602 and ventricular EGM 622 sensed during the confirmation delay 630 or during a longer post-sensing time interval (e.g., within 20 ms to 100 ms of the Vsense signal 628). The V / A sensing ratio (or other quantitative relationship) determined when an R wave is confirmed in the absence of a CCOS event can be stored in the memory 210 and / or used by the control circuit 206 to establish or update the R wave confirmation threshold applied to the V / A sensing ratio (or other quantitative relationship) determined during future cardiac cycles when a pending Vsense event signal is followed by an Asense event signal within a confirmation delay.

[0167] In some examples, a V / A sensing ratio determined as the ratio of the ventricular EGM maximum peak amplitude 632 to the atrial EGM maximum peak amplitude 614 is cached in a memory along with multiple V / A sensing ratios determined when the Vsense signal is confirmed as a true R wave based on the expiration of a confirmation delay without an Asense event signal. The R-wave confirmation threshold can be determined as a representative value of multiple cached V / A sensing ratios, such as a mean, median, trimmed mean, trimmed median, minimum, or other representative value. In other examples, the control circuit 206 can use a single V / A sensing ratio to update or establish the R-wave confirmation threshold. In conjunction with Fig. 9 An exemplary technique for establishing or updating an R-wave confirmation threshold applied to a V / A sensing ratio is described. As described above, in other examples, the quantitative relationship between atrial and ventricular EGM signal characteristics may be determined as a difference, sum, product, or any combination thereof rather than a ratio.

[0168] In response to asserting the Vsense event signal 628, the sensing circuit 204 may apply a post-sensing ventricular blanking period 636 to the ventricular EGM signal 622. The post-sensing ventricular blanking period 636 may have an effective start time at the time of the Vsense event signal 628. Any subsequent R-wave sensing threshold crossings during the post-sensing ventricular blanking period 636 are not sensed as an R-wave by the sensing circuit 204, do not result in another Vsense event signal being generated by the ventricular sensing channel 205, or are ignored by the control circuit 206 in controlling a ventricular pacing pulse.

[0169] In response to asserting the Vsense event signal 628, the sensing circuit 204 may apply a post-ventricular atrial blanking period 638 to the atrial EGM signal 602. The post-ventricular atrial blanking period 638 may have an effective start time at the time of the Vsense event signal 628. Any subsequent P-wave sensing threshold crossings during the post-ventricular atrial blanking period 638 are not sensed as P waves, do not result in the generation of an Asense event signal by the atrial sensing channel 203, or are ignored by the control circuit 206 when controlling atrial pacing pulses and ventricular pacing pulses. Figure 8 As shown, the post-sensing ventricular blanking period 636 and the post-ventricular atrial blanking period 638 can be longer than the confirmation delay 630, but are not necessarily longer than the confirmation delay 630.

[0170] Although in Figure 8 Not shown, but as generally described above, the control circuit 206 can initiate one or more pacing intervals, such as an AV pacing interval, an atrial LRI, a ventricular LRI, a rate response interval, or a rate smoothing interval, in response to a confirmed cardiac event signal. A pending pacing pulse scheduled for delivery at the expiration of a running pacing interval at the time of a confirmed cardiac event signal, a P wave, or an R wave can be suppressed based on the current pacing mode in effect. In other examples, a pacing pulse can be triggered in response to a confirmed P wave or a confirmed R wave, such as to provide atrial or ventricular safety pacing or to initiate an AV pacing interval.

[0171] When the ventricular pacing escape interval expires during the confirmation delay 610 after the Asense event signal 608, a pending ventricular pacing pulse may be delivered at the expiration of the pacing escape interval before the Vsense event signal is received after the Asense event signal 608. The confirmation delay 610 initiated in response to the Asense event signal 608 may be canceled (e.g., terminated without further analyzing the atrial and ventricular EGM signals). In other examples, the pending ventricular pacing pulse may be delayed or suppressed until the confirmation delay 610 expires. If the Asense event signal 608 is confirmed (based on the absence of a Vsense event signal during the confirmation delay 610 or based on a quantitative relationship analysis of atrial and ventricular EGM signal characteristics), the pending ventricular pacing pulse may be delivered at the expiration of the confirmation delay 610. If the Vsense event signal is received during the confirmation delay 610 and the Vsense event signal is confirmed based on the V / A sensing ratio or other quantitative relationship, the pending ventricular pacing pulse may be suppressed.

[0172] When the atrial pacing escape interval expires during the confirmation delay 630 after the Vsense event signal 628, a pending atrial pacing pulse may be delivered when the atrial pacing escape interval expires before the Asense event signal is received after the Vsense event signal 628. The confirmation delay 630 initiated in response to the Vsense event signal 628 may be canceled (e.g., terminated without further analyzing the atrial and ventricular EGM signals). In other examples, the pending atrial pacing pulse may be delayed or suppressed until the confirmation delay 630 expires. If the Vsense event signal 628 is confirmed, the pending atrial pacing pulse may be delivered at the expiration of the confirmation delay 630. If the Asense event signal is received during the confirmation delay 630 and the Asense event signal is subsequently confirmed based on the V / A sensing ratio (or other quantitative relationship), the pending atrial pacing pulse may be suppressed (e.g., canceled).

[0173] Fig. 9 700 is a flow chart of a method performed by a pacemaker 14 for establishing or updating a P wave confirmation threshold and / or an R wave confirmation threshold according to some examples. The control circuit 206 can be configured to establish and / or adjust the P wave confirmation threshold and / or the R wave confirmation threshold based on an analysis of the atrial EGM signal and / or the ventricular EGM signal. The analysis of the atrial EGM signal and / or the ventricular EGM signal can be performed to determine one or more quantitative relationships between the atrial EGM signal and the ventricular EGM signal when CCOS does not occur and / or when CCOS occurs. The control circuit 206 can determine and use the quantitative relationship to set or adjust the P wave confirmation and / or R wave confirmation threshold.

[0174] exist Fig. 9 In the exemplary method of , at block 702, the control circuit 206 may receive an atrial event signal as an Asense event signal from the sensing circuit 204, the Asense event signal being generated by the atrial sensing channel 204 in response to a P-wave sensing threshold crossing of the atrial EGM signal. As described above, in other examples, the control circuit 206 may receive the atrial event signal by receiving the atrial EGM signal from the sensing circuit 204 and identifying the P-wave from the atrial event signal based on a threshold crossing, waveform morphology, or other waveform features of the atrial EGM signal.

[0175] In some cases, when the atrial pacing escape interval expires before the Asense event signal is received, an atrial pacing pulse (Apace) may be delivered. In this case, the control circuit 206 may proceed to box 710 to wait for the Vsense signal. In response to receiving the Asense event signal at box 702, the control circuit 206 may start a confirmation delay at box 704. If the Vsense event signal is received at box 706 (or the R wave is identified by the control circuit 206 from the received ventricular EGM signal) before the confirmation delay expires, the control circuit 206 may ignore the Asense event signal for the purpose of establishing or updating the P wave confirmation threshold. The control circuit 206 may return to box 702 to wait for the next Asense signal received outside the confirmation delay.

[0176] In other examples, the control circuit 206 may proceed to block 710 to wait for a Vsense event signal to be received outside of the acknowledge delay. Fig. 9 Not shown, but understood, in response to receiving a Vsense signal at box 706 during a confirmation delay following the Asense signal at box 702, the control circuit 206 may determine a V / A sensing ratio to confirm one of the Asense or Vsense event signals based on the current value of the P-wave confirmation threshold (and / or the R-wave confirmation threshold) according to any of the examples described above.

[0177] When the Vsense event signal is not received during the confirmation delay following the Asense event signal (the "No" branch of block 706), the control circuit 206 may determine the V / A sense ratio (or VA difference) at block 708, as described above in conjunction with Figure 8 Generally described. For example, refer to Figure 8 , the control circuit 206 can determine the ratio of the ventricular EGM maximum peak amplitude 634 to the atrial EGM maximum peak amplitude 612 as the V / A sensing ratio at box 708. The control circuit 206 can use the determined V / A sensing ratio to establish or update the P wave confirmation threshold, as further described below. In this way, the V / A sensing ratio (or other quantitative relationship determined at box 708) can be referred to as a "reference quantitative relationship" because it is determined by the control circuit 206 when an Asense event signal is received but a Vsense event signal is not received within the confirmation delay. Therefore, the reference quantitative relationship is the relationship between the atrial EGM signal characteristics and the ventricular EGM signal characteristics when CCOS does not occur. The reference quantitative relationship can be used to set or adjust the P wave confirmation threshold of the V / A sensing ratio that is subsequently applied when the Asense event signal and the Vsense event signal occur within each other's confirmation delay.

[0178] See again Fig. 9, the control circuit 206 may wait at block 710 for a Vsense event signal received from the sensing circuit 204 outside the confirmation delay. In other examples, the control circuit 206 may receive a ventricular event signal by receiving a ventricular EGM signal from the sensing circuit 204 and identifying an R wave based on a threshold crossing, a waveform morphology, or other waveform features. If a ventricular pacing pulse (Vpace) occurs before the Vsense event signal is received outside the confirmation delay, the control circuit 206 may return to block 702 to wait for the next Asense signal. When the Vsense event signal is received at block 710 outside the confirmation delay, the control circuit 206 may initiate a confirmation delay at block 712 in response to the received Vsense event signal.

[0179] If an Asense event signal is received at block 714 before the confirmation delay expires (the "yes" branch of block 714), the control circuit 206 may return to block 710 to wait for another Vsense event signal received beyond the confirmation delay. Fig. 9 As shown in , the control circuit 206 may return to box 702 to wait for an Asense event signal received outside the confirmation delay. In general, when an Asense event signal is received and there is no Vsense event signal within the confirmation delay and / or when a Vsense event signal is received and there is no Asense event signal within the confirmation delay, the control circuit 206 may wait for the next sensed cardiac event signal (atrial or ventricular) occurring outside the running confirmation delay for obtaining the V / A sensing ratio (or other quantitative relationship) from the atrial and ventricular EGM signals. The P wave confirmation threshold and the R wave confirmation threshold may not be updated based on the sensed EGM signal when both the Asense event signal and the Vsense event signal occur within each other's confirmation delay. However, in this case, the control circuit 206 may use the technology disclosed herein to confirm one of the Asense event signal or the Vsense event signal based on the current value or nominal value of the P wave confirmation threshold and / or the R wave confirmation threshold.

[0180] When the Asense event signal is not received before the confirmation delay following the Vsense event signal expires (the "No" branch of block 714), the control circuit 206 may determine the V / A sense ratio (or VA difference or other quantitative relationship) at block 716. Figure 8 The V / A sensing ratio is determined as generally described. For example, referring to Figure 8, the control circuit 206 may determine the ratio of the ventricular EGM maximum peak amplitude 632 to the atrial EGM maximum peak amplitude 614 as the V / A sensing ratio at box 716. The control circuit 206 may use the determined V / A sensing ratio to establish or update the R wave confirmation threshold at box 718. The V / A sensing ratio (or other quantitative relationship) determined by the control circuit 206 at block 716 when a Vsense event signal is received and an Asense event signal is not received within the confirmation delay may be referred to as a "reference quantitative relationship" of atrial EGM signal characteristics and ventricular EGM signal characteristics when CCOS does not occur. As described below, the reference quantitative relationship may be used to set or adjust the R wave confirmation threshold.

[0181] Using the V / A sensing ratio determined at box 708 for the Asense event signal confirmed without a Vsense event signal during the confirmation delay, the control circuit 206 can establish or update the P wave confirmation threshold at box 718. The P wave confirmation threshold can be set to a percentage of a V / A sensing ratio or a mean, median, maximum, or other representative value of multiple V / A sensing ratios determined for one or more confirmed P waves without cross-cavity excessive sensing. The percentage can be 100%, 110%, 120%, 150%, or other selected percentages. In some examples, the P wave confirmation threshold can be set to a percentage of a representative V / A sensing ratio plus an offset. The offset can be a positive 0.1, 0.2, 0.3, 0.5, 1.0, or other selected offset. The offset can be scaled based on the atrial EGM maximum peak amplitude, the ventricular EGM maximum peak amplitude, or the currently determined V / A sensing ratio for the Asense event signal determined or received at box 702. The P wave confirmation threshold may be set to be greater than all V / A sense ratios determined for one or more P waves confirmed by the control circuit 206 based on the absence of a Vsense event signal received during a confirmation delay period after receipt of an Asense event signal.

[0182] A previously established P wave confirmation threshold may be updated based on the V / A sensing ratio determined at block 708. In some examples, the P wave confirmation threshold may be an initial, user-programmed, or default value, such as 0.5, 0.7, or 1.0 as illustrative examples. The P wave confirmation threshold may be updated at block 718 by adjusting the P wave confirmation threshold by an increment or decrement (e.g., ±0.05, 0.1, 0.2, or other increments or decrements) toward the V / A sensing ratio determined at block 708. In other examples, the P wave confirmation threshold may be updated to be greater than the V / A sensing ratio determined at block 708. The control circuit 206 may not adjust the P wave confirmation threshold to be greater than the R wave confirmation threshold.

[0183] Using the V / A sensing ratio determined at box 716 for the Vsense event signal confirmed without an Asense event signal during the confirmation delay, the control circuit 206 may establish or update the R wave confirmation threshold at box 718. The R wave confirmation threshold may be set to a percentage of a V / A sensing ratio or a mean, median, minimum, or other representative value of multiple V / A sensing ratios determined for one or more confirmed R waves without cross-chamber excessive sensing. The percentage may be 60%, 70%, 80%, 90%, or any other selected percentage. In some examples, the R wave confirmation threshold may be set to a percentage of a representative V / A sensing ratio minus an offset. The offset may be 0.1, 0.2, 0.3, 0.5, 1.0, or other selected offsets. The offset may be scaled based on the maximum peak amplitude of the atrial EGM, the maximum peak amplitude of the ventricular EGM, or the V / A sensing ratio determined for the current Vsense event signal received at box 710. The offset may be scaled based on a representative V / A sensing ratio determined based on a plurality of buffered V / A sensing ratios determined based on R waves confirmed without CCOS. The R wave confirmation threshold may be set to be less than all V / A sensing ratios determined for one or more R waves confirmed by the control circuit 206 based on not receiving an Asense event signal during a confirmation delay after receiving a Vsense event signal.

[0184] The previously established R-wave confirmation threshold may be updated at block 718 based on the V / A sensing ratio determined at block 716. In some examples, the R-wave confirmation threshold may be an initial, user-programmed, or default value, such as 1.5, 2.0, or 2.5 as illustrative examples. The R-wave confirmation threshold may be updated at block 718 by adjusting the R-wave confirmation threshold by an increment or decrement (e.g., ±0.1, 0.2, 0.5, or other increments or decrements) toward the V / A sensing ratio determined at block 716. In other examples, the R-wave confirmation threshold may be updated at block 718 to be less than the V / A sensing ratio determined at block 716. The control circuit 206 may not adjust the R-wave confirmation threshold to be less than the P-wave confirmation threshold.

[0185] In some examples, the control circuit 206 establishes or updates the P wave confirmation threshold and the R wave confirmation threshold to two different values ​​at box 718. In other examples, the control circuit 206 may establish a confirmation threshold that is applied to the V / A sensing ratio to confirm the P wave and the R wave. The common P wave confirmation threshold and the R wave confirmation threshold may be determined between the V / A sensing ratio determined at box 708 and the V / A sensing ratio determined at box 716. In some examples, the control circuit 206 may cache a plurality of V / A sensing ratios for P waves confirmed without CCOS and a plurality of V / A sensing ratios for R waves confirmed without CCOS sensing. The common P wave confirmation threshold and the R wave confirmation threshold may be determined as the mean of the cached V / A sensing ratios or another value between the V / A sensing ratios of the confirmed P wave and the V / A sensing ratios of the confirmed R wave. In this case, the P wave confirmation threshold and the R wave confirmation threshold may be equal. As described above, it should be understood that the quantitative relationship between atrial EGM signal characteristics and ventricular EGM signal characteristics can be determined as a difference, such as a VA (or AV) difference, rather than a ratio as described herein, for performing a comparative analysis of two signals sensed within a confirmation delay of each other.

[0186] For illustration, the flowchart 700 shows that the V / A sensing ratio is determined at box 708 when the Asense event signal is received and the V / A sensing ratio is determined at box 716 when the Vsense event signal is received. It should be understood that the control circuit 206 can determine the V / A sensing ratio only at box 708 or only at box 716. The V / A sensing ratio determined for both the Asense event signal (no Vsense event signal within the confirmation delay) and the Vsense event signal (no Asense event signal within the confirmation delay) may not be required for establishing or updating the confirmation threshold at box 718. When the Asense event signal is received without the Vsense event signal within the confirmation delay or when the Vsense event signal is received without the Asense event signal within the confirmation delay, the confirmation threshold can be updated at box 718 based on the V / A sensing ratio determined according to the atrial and ventricular EGM signals. Based on the V / A sensing ratio determined at box 708 or box 716, a single confirmation threshold can be established, or different P wave confirmation thresholds and R wave confirmation thresholds, but not necessarily both. For example, the P wave confirmation threshold may be set to a fraction of the V / A sensing ratio determined at block 708 (less than the V / A sensing ratio), and the R wave confirmation threshold may be set to a multiple of the V / A sensing ratio determined at block 708 (greater than the V / A sensing ratio). In another example, the P wave confirmation threshold may be set to a first percentage of the V / A sensing ratio determined at block 716, and the R wave confirmation threshold may be set to a second percentage greater than the first percentage of the V / A sensing ratio determined at block 716. In other examples, a single confirmation threshold may be established based on the V / A sensing ratio determined at blocks 708 or 716. When the V / A sensing ratio determined for subsequent Asense event signals and Vsense event signals received within a single confirmation delay of each other is less than the confirmation threshold, the Asense event signal may be confirmed by the control circuit 206 as a true P wave. The Vsense event signal may be identified as a CCOS event. When the V / A sensing ratio determined for subsequent Asense event signals and Vsense event signals received within a confirmation delay of each other is greater than a single confirmation threshold, the Asense event signal can be identified by the control circuit 206 as a CCOS event (e.g., a far-field R-wave), and the Vsense event signal can be confirmed as a true sensed R-wave.

[0187] The control circuit 206 may perform the process of flowchart 700 upon pacemaker implantation, during patient follow-up, on a periodic schedule (e.g., once per minute, once per hour, once per day, etc.), or on a beat-to-beat basis (e.g., simultaneously or in parallel with the above-described techniques for confirming cardiac sensed event signals). In other examples, the process of flowchart 700 may additionally or alternatively be triggered for execution when atrial sensitivity, ventricular sensitivity, or another sensing control parameter for sensing cardiac event signals is programmed or adjusted to a new value. In response to a pacing mode switch, or when the pacemaker behaves differently than expected, for example, when the atrial pacing burden is higher than the atrial pacing burden expected for the patient (e.g., greater than a programmed threshold atrial pacing burden), when the asynchronous ventricular pacing burden is higher than the asynchronous ventricular pacing burden expected for the patient (e.g., greater than a programmed threshold ventricular pacing burden), when the percentage of atrial synchronous ventricular pacing pulses delivered by the pacemaker 14 is less than a threshold percentage of all delivered ventricular pacing pulses or all ventricular electrical events (sensed and paced), the process of flowchart 700 may be triggered for execution. In some examples, the control circuit 206 may be configured to detect an arrhythmia, such as an atrial tachyarrhythmia, ventricular tachycardia, or ventricular fibrillation. For example, the control circuit 206 may detect a tachyarrhythmia based on the rate of the atrial sensed event signal and / or the ventricular sensed event signal. The process of flowchart 700 may be triggered for execution when the control circuit 206 has detected or is detecting an arrhythmia.

[0188] Fig.10 is a flow chart 750 of a method for establishing a bandpass filter cutoff frequency for sensing atrial EGM signals and ventricular EGM signals, according to some examples. Fig.10 The same numbered boxes in the above correspond to the Fig. 9 During the process of flowchart 750, control circuit 206 may adjust the bandpass cutoff frequency of atrial sensing channel 203 and / or ventricular sensing channel 205 to maximize the difference between the V / A sensing ratios (or other quantitative relationships) determined when a true P wave is sensed and / or when a true R wave is sensed. Atrial sensing channel filter 224 (see Figure 4 ) can be adjusted to maximize the P wave amplitude in the atrial EGM signal and minimize the far-field R wave amplitude. The ventricular sensing channel filter 254 (see Figure 4 )'s high and / or low cutoff frequencies can be adjusted to maximize the R-wave amplitude in the ventricular EGM signal and minimize the cross-chamber P-wave amplitude.

[0189] As above combined Fig. 9Generally described, when an Asense event signal is received (block 702) and a Vsense event signal is not received during the confirmation delay (the "No" branch of block 706), the control circuit 206 may determine the V / A sense ratio at block 708. When a Vsense event signal is received (block 710) and an Asense event signal is not received during the confirmation delay (the "No" branch of block 714), the control circuit 206 may determine the V / A sense ratio at block 716.

[0190] The control circuit 206 may determine, at block 752, a V / A sensing ratio difference between the V / A sensing ratio determined at block 708 for a true P wave and the V / A sensing ratio determined at block 716 for a true R wave. In some examples, the control circuit 206 may adjust the bandpass filter settings of the atrial sensing channel 203 and / or the ventricular sensing channel 205 one or more times and repeat the process of determining the V / A sensing ratio at blocks 708 and 716 for multiple filter settings to enable comparison of the V / A sensing ratio differences determined for different combinations of filter cutoff frequencies. At block 754, the control circuit 206 may determine whether another filter setting remains to be evaluated. The control circuit 206 can advance (or return) to box 756 to adjust the high pass cutoff frequency and / or low pass cutoff frequency of the atrial sensing channel filter 224 and / or the high pass frequency and / or low pass frequency of the ventricular sensing channel filter 254, thereby repeating the process of flowchart 750 to determine the V / A sensing ratio difference at box 752 for different filter settings.

[0191] In other examples, the control circuit 206 may compare the determined V / A sensing ratio difference to a threshold difference at block 754. If the V / A sensing ratio difference is not greater than the threshold difference, the control circuit 206 may adjust the low and / or high cutoff frequencies of the atrial sensing channel filter 224 and / or the ventricular sensing channel filter 254 at block 756 and repeat the process for determining the V / A sensing ratio difference until the V / A sensing ratio difference is greater than the threshold difference at block 754. By way of example, the V / A sensing ratio difference may be required to be at least 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.25, 1.5, or 2.0, but is not limited thereto.

[0192] When determining the V / A sensing ratio difference for multiple filter settings, the control circuit 206 may determine the combination of bandpass filter settings that results in the maximum V / A sensing ratio difference at block 756. The control circuit 206 may set the cutoff frequencies of the atrial sensing channel filter 224 and the ventricular sensing channel filter 254 according to the filter settings that result in the maximum V / A sensing ratio difference. In other examples, the control circuit 206 may set the filter settings at block 756 according to the bandpass filter cutoff frequencies that result in the V / A sensing ratio difference being greater than the threshold difference at block 754.

[0193] In some examples, the control circuit 206 may use other criteria when setting the bandpass filter settings at block 756. For example, the control circuit 206 may identify a combination of bandpass filter settings that results in a maximum P wave amplitude in the atrial EGM signal, a maximum R wave amplitude in the ventricular EGM signal, and a V / A sensing ratio difference greater than a threshold difference determined at block 752.

[0194] In addition, in addition to or in place of the V / A sensing ratio, a different quantitative relationship may be used. The control circuit 206 may determine the quantitative ratio as a difference, such as a VA difference or an AV difference, at boxes 708 and 716. At box 752, the control circuit 206 may determine the difference or ratio between the quantitative relationship determined at box 706 when only the Asense signal is received and the quantitative ratio determined at box 716 when only the Vsense signal is received. The control circuit 206 may adjust at least one of the atrial EGM signal low-pass filter cutoff frequency, the atrial EGM signal high-pass filter cutoff frequency, the ventricular EGM signal low-pass filter cutoff frequency, and / or the ventricular EGM signal high-pass filter cutoff frequency to maximize the difference between the two quantitative relationships determined at boxes 706 and 716.

[0195] In some examples, the process of flowchart 750 may include receiving user input. For example, control circuit 206 may send atrial EGM signals and ventricular EGM signals to external device 20 (see Figure 1). When the EGM signal is displayed to the user on the display unit 54, the bandpass filter settings of the atrial sensing channel filter 224 and the ventricular sensing channel filter 254 can be adjusted according to a plurality of available settings. The EGM signal can be annotated with an Asense event marker, a Vsense event marker, a maximum peak P wave amplitude, a maximum peak R wave amplitude, and / or a V / A sensing ratio. The user can select filter settings that can be reported by the control circuit 206 or the external device processor 52, which result in the maximum V / A sensing ratio of the true R wave, the lowest V / A sensing ratio of the true P wave, the maximum sensing ratio difference, the maximum P wave peak amplitude, the maximum R wave peak amplitude, the lowest far-field R wave peak amplitude in the atrial EGM signal, the lowest cross-channel P wave peak amplitude in the ventricular EGM signal, or any combination thereof.

[0196] After setting the filter bandpass cutoff frequency for each of the atrial sensing channel 203 and the ventricular sensing channel 205 at box 756, the control circuit 206 can establish a P wave confirmation threshold and an R wave confirmation threshold at box 718. The P wave confirmation threshold and the R wave confirmation threshold can be established based on the V / A sensing ratio determined using the bandpass filter cutoff frequency set at box 756. In some examples, once the bandpass filter setting is set at box 756, the control circuit 206 can establish the P wave confirmation threshold as the mean, median, or other representative value of the V / A sensing ratio determined when an Asense event signal is received and there is no Vsense event signal during the confirmation delay period. The control circuit 206 can establish the R wave confirmation threshold as the mean, median, or other representative value of the V / A sensing ratio determined when a Vsense event signal is received and there is no Asense event signal during the confirmation delay period.

[0197] In some examples, when the V / A sensing ratio is closer to the P wave confirmation threshold than the R wave confirmation threshold, the control circuit 206 may confirm a true P wave. When the V / A sensing ratio is closer to the R wave confirmation threshold than the P wave confirmation threshold, the control circuit 206 may confirm a true R wave. In other examples, as described above, when the V / A sensing ratio is less than the P wave confirmation threshold, a true P wave may be confirmed by the control circuit 206. When the V / A sensing ratio is greater than the R wave confirmation threshold, a true R wave may be confirmed.

[0198] Fig.11800 is a flowchart of a method for confirming a sensed cardiac event signal that may be performed by a pacemaker 14 according to another example. The above-described technique generally provides a method performed by a medical device for identifying a true cardiac event signal and a CCOS event signal when the two cardiac event signals occur within a confirmation delay of each other. In some cases, one sensing channel of the sensing circuit 204 may over-sense the event signal when the other sensing channel under-senses the true event signal. In this case, the second event signal may not be received within the confirmation delay of the over-sensed signal. In other cases, both sensing channels may over-sense the same event signal that is not a true event signal intended to be sensed by either sensing channel. The process of flowchart 800 provides a technique for confirming a true event signal or identifying an over-sensed event signal when one sensing channel over-senses an event signal and the other channel under-senses the event signal and / or when both channels over-sense an event signal.

[0199] At box 802, when the confirmation delay is not yet running, the control circuit 206 receives a first cardiac event signal, such as an Asense event signal or a Vsense event signal. At box 804, the control circuit 206 can initiate the confirmation delay in response to receiving the first cardiac event signal outside the confirmation delay (and outside any applicable blanking period). At box 806, the control circuit 206 can determine the V / A sensing ratio (or another quantitative relationship) based on the atrial EGM signal and the ventricular EGM signal sensed during the confirmation delay or during a specified post-sensing time interval. In this example, the V / A sensing ratio can be determined by the control circuit 206 in response to the first sensing event signal, regardless of whether the second sensing event signal is received during the confirmation delay.

[0200] At box 808, the control circuit 206 may determine whether the V / A sensing ratio meets the confirmation threshold for confirming the first event signal. For example, if the first event signal is an Asense event signal, the control circuit 206 may determine at box 808 whether the V / A sensing ratio is less than the P wave confirmation threshold. If the first event signal is a Vsense event signal, the control circuit 206 may determine at box 808 whether the V / A sensing ratio is greater than the R wave confirmation threshold. When the V / A sensing ratio meets the threshold requirement for confirming the first cardiac event signal received at box 802 (the "yes" branch of box 808), the control circuit 206 may confirm the first cardiac event signal at box 810. At box 812, the control circuit 206 may perform a pacing and / or sensing response based on the confirmed first cardiac event signal and the currently operating pacing mode according to any exemplary response described herein. The control circuit 206 may return to box 802 to wait for the next cardiac event signal received outside the confirmation delay.

[0201] If the V / A sensing ratio does not meet the first event confirmation threshold requirement at box 808 ("No" branch), the control circuit 206 may determine whether a second cardiac event signal (e.g., from another sensing channel of the sensing circuit 204) is received at box 814 before the confirmation delay expires. If the second event signal is not received, and the V / A sensing ratio does not meet the first event confirmation threshold requirement at box 808, the control circuit 206 may identify the first cardiac event signal as an oversensing event signal at box 816. The first cardiac event signal may be a CCOS event signal. For example, when the ventricular sensing channel 204 under-sensed (did not sense) a certain R wave, the atrial sensing channel 203 may over-sensed a far-field R wave (the same R wave). In other cases, the ventricular sensing channel 205 may over-sensed a P wave that was under-sensed by the atrial sensing channel 203. In another example, the ventricular sensing channel 205 may over-sensed a T wave that was not sensed by the atrial sensing channel 203. In yet other examples, one sensing channel 203 or 205 may over-sensing non-cardiac event signals, such as electromagnetic interference (EMI) noise signals or other EGM noise contamination.

[0202] When the first cardiac event signal is identified as an oversensing event signal at block 816, the control circuit 206 may return to block 802 to wait for the next cardiac event signal received beyond the confirmation delay. For the purpose of providing a sensing and / or pacing response, the control circuit 206 may ignore the oversensing event signal.

[0203] Referring again to box 814, if a second event signal is received during the confirmation delay period (the "yes" branch of box 814), the control circuit 206 can optionally determine at box 818 whether the V / A sensing ratio determined at box 806 meets the confirmation threshold requirement for confirming the second sensed event signal. For example, if the second cardiac event signal received during the confirmation delay period is a Vsense event signal, the control circuit 206 can determine whether the V / A sensing ratio is greater than the R wave confirmation threshold. If the second cardiac event signal received during the confirmation delay period is an Asense event signal, the control circuit 206 can determine whether the V / A sensing ratio is less than the P wave confirmation threshold. If the V / A sensing ratio meets the second cardiac event confirmation threshold requirement (the "yes" branch of box 818), the control circuit 206 can confirm the second cardiac event at box 822. In other examples, box 818 is optional. When the second cardiac event signal is received at block 814 before the confirmation delay expires and the V / A sensing ratio does not satisfy the first cardiac event signal confirmation threshold at block 808 , the second cardiac event signal may be confirmed at block 822 .

[0204] In response to confirming the second cardiac event signal, control circuit 206 may perform one or more pacing and / or sensing responses based on the confirmed second cardiac event signal and in accordance with the currently operating pacing mode at block 824. Control circuit 206 may return to block 802 to await the next cardiac event signal received beyond the confirmation delay.

[0205] When the V / A sensing ratio determined at box 806 does not satisfy the first cardiac event confirmation threshold or the second cardiac event confirmation threshold (the "No" branch of box 818), the control circuit 206 may determine at box 820 that both the first cardiac event signal and the second cardiac event signal are oversensing event signals. In some cases, both the atrial sensing channel 203 and the ventricular sensing channel 205 may oversensing T waves, EMI signals, or other noise signals. When the V / A sensing ratio does not satisfy either the P wave confirmation threshold or the R wave confirmation threshold, the control circuit 206 may identify the Asense event signal and the Vsense event signal received within the confirmation delay of each other as oversensing event signals at box 820. In response to identifying the oversensing event signals received from both the atrial sensing channel 203 and the ventricular sensing channel 205, the control circuit 206 may return to box 802. The control circuit 206 may ignore the oversensing event signal for the purpose of providing a sensing and / or pacing response (such as initiating (or restarting) a pacing interval, inhibiting a pacing pulse, applying a blanking period, etc.).

[0206] Fig.12 900 is a flow chart of a method for sensing a cardiac event signal by a medical device and providing a pacing and / or sensing response to the sensed cardiac event signal according to another example. In some examples, when a pacing pulse is delivered, post-pacing polarization artifacts may interfere with confirming the sensed event signal. Therefore, in some examples, when a pacing pulse is delivered (box 902), the control circuit 206 can optionally start a polarization delay at box 904. For example, a timer can be started by the control circuit 206 to count down a polarization delay of 30ms, 50ms, 80ms, 100ms, 150ms, or other selected value of polarization delay, thereby allowing any post-pacing polarization artifacts to decay in time. It should be understood that while waiting for the delivery of a pacing pulse at box 902, the control circuit 206 can be receiving an Asense event signal and / or a Vsense event signal and performing the method disclosed herein for confirming a sensed cardiac event signal.

[0207] When a pacing pulse is delivered by the pulse generator 202 at box 902, depending on the pacing mode, the control circuit 206 can restart the pacing escape interval in response to the delivered pacing pulse at box 904 to schedule the next pending pacing pulse. The pacing pulse delivered at box 902 can be an atrial pacing pulse, so that an atrial pacing escape interval (e.g., an atrial LRI or a temporary rate response interval or a rate smoothing interval) can be restarted at box 904. When an atrial pacing pulse is delivered at box 902 and the pacing mode is an atrial synchronous ventricular pacing mode, an AV pacing interval can be initiated at box 904. In other cases, the pacing pulse delivered at box 902 can be a ventricular pacing pulse, so that a ventricular pacing escape interval (e.g., a ventricular LRI or a temporary rate response interval or a rate smoothing interval) can be restarted at box 904 according to the effective operating pacing mode.

[0208] When a sensed event signal is received by the control circuit 206 at block 906 outside of a blanking period or a previously initiated confirmation delay, the control circuit 206 may determine at block 908 whether the polarization delay has expired. If not, the first sensed event signal may be confirmed at block 922 without initiating a confirmation delay. If the polarization delay expires (the "yes" branch of block 908), the control circuit 206 may initiate a confirmation delay at block 910. As generally described above, if a second sensed event signal is not received (the "no" branch of block 912) and the confirmation delay expires (the "yes" branch of block 914), the first sensed event signal may be confirmed by the control circuit 206 at block 922. If a second sensed event signal is received at block 912 before the confirmation delay expires (the "yes" branch of block 912), the control circuit 206 may determine at block 918 a quantitative relationship of the atrial EGM signal characteristic to the ventricular EGM signal characteristic according to any of the examples described above. The control circuit 206 compares the quantitative relationship to a confirmation threshold at block 920 to confirm the first sensed event signal (at block 922) or the second sensed event signal (at block 924) according to any of the exemplary methods provided herein.

[0209] Control circuit 206 may control pulse generator 202 to provide a pacing response and / or control sensing circuit 204 to provide a sensing response based on the confirmed sensing event signal at block 926. Based on which of the first sensing event signal or the second sensing event signal is confirmed, any of the exemplary pacing and / or sensing responses described herein may be performed at block 926.

[0210] In some cases, the pacing escape interval may expire during the confirmation delay period initiated at block 910. Referring again to block 914, if the confirmation delay is initiated and has not expired (the "No" branch of block 914) and the pacing escape interval expires during the confirmation delay period (the "Yes" branch of block 915), the control circuit 206 may respond to the expired pacing escape interval based on which cardiac chamber the pending pacing pulse is scheduled to be delivered to and / or which sensing channel (the atrial sensing channel or the ventricular sensing channel) generated the first sensed event signal at block 906.

[0211] For example, if an Asense event signal is received as a first cardiac chamber sensed event signal at box 906 and a ventricular pacing escape interval expires during the confirmation delay, the scheduled pending ventricular pacing pulse (for delivery to a second cardiac chamber) may be delivered at box 928 (the "No" branch of box 916). When a Vsense event signal is not received during the confirmation delay (the "No" branch of box 912) and a ventricular pacing escape interval expires after the Asense event signal triggers initiation of the confirmation delay, a ventricular pacing pulse may be delivered at box 928 in response to the expired ventricular pacing escape interval (which may be an AV delay, a ventricular LRI, a rate response interval, a rate smoothing interval, etc.). The confirmation delay may terminate at box 930. For example, the Asense event signal may be confirmed so that any atrial post-blanking period and refractory period and / or atrial pacing escape interval that has a valid initiation time at the moment of the P wave sensing threshold crossing may be initiated. Control circuit 206 may return to block 904 to initiate the polarization delay and restart the ventricular pacing escape interval as needed depending on the operating pacing mode.

[0212] Fig.13 950 is a diagram of an Asense event signal 956 that triggers the initiation of a confirmation delay 955 and a ventricular pacing interval 952 that expires during the confirmation delay 955. In this example, the ventricular pacing interval is an AV pacing interval that expires before the Vsense event signal is received by the control circuit 206. In this case, the atrial event (A) 951 can be a delivered atrial pacing pulse. In other cases, the atrial event 951 can be a confirmed Asense event signal. The control circuit 206 can initiate the AV pacing interval 952 in response to the atrial event 951. In response to the atrial event 951 being an atrial pacing pulse, the control circuit 206 can initiate the polarization delay 966 as described above (see Fig.12 904) and initiates an AV pacing interval 952 to schedule a ventricular pacing pulse (VP) 954. When a Vsense event signal is not received before the AV pacing interval 952 expires, the scheduled ventricular pacing pulse 954 may be delivered during a confirmation delay 955 when the AV pacing interval 952 expires.

[0213] See again Fig.12 , if the pacing escape interval that expires during the confirmation delay at box 915 is for scheduling a pacing pulse in the first cardiac chamber at the time of initiation (the "yes" branch of box 916), the control circuit 206 can control the pulse generator 202 to suppress the pending pacing pulse until the confirmation window expires. For example, when the atrial pacing escape interval expires at box 915 and the first chamber sensed event signal received at box 906 is an Asense event signal, the control circuit 206 can return to box 912 to wait for the second chamber (Vsense) event signal and / or wait for the confirmation delay to expire at box 914. If the Asense event signal is confirmed at box 922, the pending atrial pacing pulse can be canceled at box 926. If it is determined that the Asense event signal is a CCOS signal and the second Vsense event signal is confirmed at box 924, the pending atrial pacing pulse can be delivered at box 926.

[0214] In other examples, if a first cardiac chamber (an atrial chamber or a ventricular chamber) pacing escape interval expires such that a pending pacing pulse is scheduled to be delivered during a confirmation delay period following a first cardiac chamber sensed event signal from the same cardiac chamber (e.g., an atrial pacing escape interval expires during a confirmation delay period initiated in response to an Asense signal, or a ventricular pacing escape interval expires during a confirmation delay period initiated in response to a Vsense signal), the scheduled pacing pulse may be canceled. The confirmation delay may be terminated, and the first chamber event signal received at block 906 may be responded to by control circuitry 206 as a confirmed sensed event.

[0215] See again Fig.12 At box 915, if the atrial pacing escape interval expires during the confirmation delay at box 915 and the first chamber sensed event signal received at box 906 is a Vsense event signal, a pending atrial (second chamber) pacing pulse may be delivered at box 928. The confirmation delay may be terminated at box 930. However, if the ventricular pacing escape interval expires at box 915 after the Vsense signal initiates the confirmation delay, the control circuit 206 may control the pulse generator 202 to delay the ventricular pacing pulse until the confirmation delay expires and the Vsense event signal is confirmed or determined to be a CCOS event. If the Vsense event signal is confirmed at box 922, the pending ventricular pacing pulse may be canceled by the control circuit 206 at box 926. If the Asense event signal is received during the confirmation delay and confirmed at box 924, the delayed pending ventricular pacing pulse may be delivered by the pulse generator 202 at box 926.

[0216] Fig.14961 is a diagram of an example of a pacing response that may be performed by control circuit 206 and pulse generator 202 when a sensed event signal is received from a sensing channel corresponding to a first cardiac chamber and a pending pacing pulse is scheduled in the same cardiac chamber during a subsequent confirmation delay. In this example, instead of delivering pending ventricular pacing pulse 957 at the expiration of AV pacing interval 952, control circuit 206 controls pulse generator 202 to delay pending ventricular pacing pulse 957 when AV pacing interval 952 expires during confirmation delay 955 initiated in response to Vsense event signal 953. Control circuit 206 may wait to determine whether Vsense event signal 953 is confirmed before delivering pending ventricular pacing pulse 957. In this example, no Asense event signal is received during confirmation delay 955, causing control circuit 206 to confirm Vsense event signal 953 at the expiration of confirmation delay 955. In response to the asserted Vsense event signal, the control circuit 206 cancels the delayed ventricular pacing pulse such that no ventricular pacing pulse is delivered due to the Vsense event signal 953 occurring prior to the expiration of the AV pacing interval 952.

[0217] Fig.15 963 is yet another example of a pacing response that may be performed by the control circuit 206 and the pulse generator 202 when a sensed event signal is received from one sensing channel and a pending pacing pulse is scheduled in the same cardiac chamber during a subsequent confirmation delay. In this example, the control circuit 206 initiates an AV pacing interval 952 in response to an atrial event 951 (which may be an atrial pacing pulse) to schedule a ventricular pacing pulse 954. A Vsense event signal 953 is received by the control circuit 206 after a polarization delay 966. The control circuit 206 initiates a confirmation delay 955. In this example, if the AV pacing interval 952 expires during the confirmation delay 955 before the Asense event signal is received during the confirmation delay 955, the pulse generator 202 may deliver the scheduled ventricular pacing pulse 954 in response to the expiration of the AV pacing interval 952. The Vsense signal 953 may be a true R wave or an over-sensed P wave. If the Vsense event signal 953 is due to an over-sensed P wave, the ventricular pacing pulse 954 can capture and pace the ventricle. If the Vsense event signal 953 is due to a true R wave, the delivered ventricular pacing pulse 954 may occur during the ventricular absolute refractory period and may not cause depolarization of the ventricle. In this case, the ventricular pacing pulse 954 can be considered safe pacing. In this example, the confirmation window 955 can terminate when the ventricular pacing pulse 954 is delivered.

[0218] Fig.16964 is a diagram of an Asense event signal 956 received by the control circuit 206 followed by a Vsense event signal 958 received during an acknowledgement delay 955. The AV pacing interval 952 initiated in response to the atrial event 951 to schedule a pending ventricular pacing pulse 957 expires during the acknowledgement delay 955 (in this case, after receiving the Vsense event signal 958). In this example, the control circuit 206 can control the pulse generator 202 to delay the pending ventricular pacing pulse 957. When the Asense event signal 956 is acknowledged at the expiration of the acknowledgement delay 955 based on the quantitative relationship determined from the atrial and ventricular EGM signal characteristics, the pulse generator 202 can deliver a delayed ventricular pacing pulse 960.

[0219] Fig.17 yes Fig.16 965 of the same events shown, except in this case, the Vsense event signal 958 received during the confirmation delay 955 prior to the expiration of the AV pacing interval 952 is asserted based on the quantitative relationship upon the expiration of the confirmation delay 955. The control circuit 206 can cancel the delayed ventricular pacing pulse 962 in response to the assertion of the Vsense event signal 958. The delayed ventricular pacing pulse 962 is not delivered, as shown by the dashed line, and is appropriately suppressed due to the receipt of the received Vsense event signal 958 during the AV pacing interval 952 that is confirmed as a true R wave.

[0220] It should be understood that, depending on the example, certain actions or events of any of the methods described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all of the actions or events described are necessary to practice the method). In addition, in some examples, actions or events may be performed simultaneously, for example, through multi-threaded processing, interrupt processing, or multiple processors, rather than sequentially. In addition, for the purpose of clarity, although certain aspects of the present disclosure are described as being performed by a single circuit or unit, it should be understood that the techniques of the present disclosure may be performed by a combination of units or circuits associated with, for example, a medical device.

[0221] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer).

[0222] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPLAs), or other equivalent integrated or discrete logic circuits. Thus, the term "processor" as used herein may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, these techniques may be fully implemented in one or more circuits or logic elements.

[0223] Therefore, medical devices have been presented in the foregoing description with reference to specific examples. It should be understood that the various aspects disclosed herein may be combined in combinations different from the specific combinations presented in the drawings. It should be understood that various modifications may be made to the referenced examples without departing from the scope of the present disclosure and the following claims.

Claims

1. A medical device, comprising: a sensing circuit configured to sense a first cardiac signal and a second cardiac signal; A control circuit, the control circuit being configured to: receiving a first event signal of the first cardiac signal from the sensing circuit; receiving a second event signal of the second cardiac signal from the sensing circuit; determining a quantitative relationship between a first characteristic of the first cardiac signal and a second characteristic of the second cardiac signal; as well as A sensed cardiac event signal is confirmed as one of the first event signal or the second event signal based on the quantitative relationship.

2. The medical device according to claim 1, wherein the control circuit is further configured to: Scheduling a cardiac pacing pulse at one of a first pacing interval or a second pacing interval different from the first pacing interval: In response to identifying the sensed cardiac event signal as the first cardiac event signal, scheduling the cardiac pacing pulse at the first pacing interval; or In response to confirming that the sensed cardiac event signal is the second cardiac event signal, scheduling the cardiac pacing pulse at the second pacing interval.

3. The medical device of claim 2, further comprising a pulse generator configured to deliver the cardiac pacing pulse scheduled at one of the first pacing interval or the second pacing interval.

4. The medical device according to any one of claims 1 to 3, wherein the sensing circuit is further configured to: sensing a first cardiac event signal in response to the first cardiac signal crossing a first sensing threshold; generating the first event signal received by the control circuit; sensing a second cardiac event signal in response to the second cardiac electrical signal crossing a second sensing threshold; as well as The second event signal is generated and received by the control circuit.

5. The medical device according to any one of claims 1 to 4, wherein the control circuit is further configured to confirm the sensed cardiac event signal based on the quantitative relationship by: comparing the quantitative relationship to a first confirmation threshold; in response to the quantitative relationship satisfying the first confirmation threshold, confirming the sensed cardiac event signal as the first cardiac event signal; as well as In response to the quantitative relationship not satisfying the first confirmation threshold, confirming the sensed cardiac event signal as the second cardiac event signal.

6. The medical device according to any one of claims 1 to 5, wherein the control circuit is further configured to: receiving the first event signal as an atrial event signal; receiving the second event signal as a ventricular event signal; when the first event signal is the atrial event signal, comparing the quantitative relationship to a P wave confirmation threshold; as well as The sensed cardiac event signal is confirmed based on the quantitative relationship by: in response to the quantitative relationship being less than the P wave confirmation threshold, confirming the sensed cardiac event signal as the atrial event signal; or In response to the quantitative relationship being greater than the P wave confirmation threshold, the sensed cardiac event signal is confirmed as a ventricular event signal.

7. The medical device according to any one of claims 1 to 5, wherein the control circuit is further configured to: receiving the first event signal as a ventricular event signal; receiving the second event signal as an atrial event signal; when the first event signal is the ventricular event signal, comparing the quantitative relationship with an R-wave confirmation threshold; and confirming the sensed cardiac event signal based on the quantitative relationship by: In response to the quantitative relationship being greater than the R-wave confirmation threshold, confirming that the sensed cardiac event signal is the ventricular event signal; or In response to the quantitative relationship being less than the R-wave confirmation threshold, confirming the sensed cardiac event signal as the atrial event signal.

8. The medical device according to any one of claims 1 to 5, wherein the control circuit is further configured to confirm the sensed cardiac event signal based on the quantitative relationship by: comparing the quantitative relationship to a P wave confirmation threshold and an R wave confirmation threshold; and Confirming that the sensed cardiac event signal is one of an atrial event signal or a ventricular event signal: In response to the quantitative relationship being closer to the P wave confirmation threshold than to the R wave confirmation threshold, confirming that the sensed cardiac event signal is the atrial event signal; or In response to the quantitative relationship being closer to the R-wave confirmation threshold than to the P-wave confirmation threshold, confirming the sensed cardiac event signal as the ventricular event signal.

9. The medical device of any one of claims 1 to 8, wherein the control circuit is further configured to determine the quantitative relationship by determining the first feature as the maximum peak amplitude of the first cardiac signal and determining the second feature as the maximum peak amplitude of the second cardiac signal.

10. The medical device of any one of claims 1 to 9, wherein the control circuit is further configured to initiate one or more blanking periods and / or one or more refractory periods based on the confirmed sensed cardiac event signal.

11. The medical device of any one of claims 1 to 10, wherein the control circuit is further configured to adjust at least one of the following: a first low pass filter cutoff frequency applied by the sensing circuit to the first cardiac signal; a first high pass filter cutoff frequency applied by the sensing circuit to the first cardiac signal; a second low pass filter cutoff frequency applied by the sensing circuit to the second cardiac signal; and / or A second high pass filter cutoff frequency is applied by the sensing circuit to the second cardiac signal.

12. The medical device according to claim 11, wherein the control circuit is further configured to: determining a first quantitative relationship between the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the first event signal from the sensing circuit and not receiving the second event signal within an acknowledgement delay time from the first event signal; determining a second quantitative relationship of the first characteristic of the first cardiac signal and the second characteristic of the second cardiac signal in response to receiving the second event signal from the sensing circuit without receiving the first event signal within an acknowledgement delay time from the first event signal; as well as determining a difference between the first quantitative relationship and the second quantitative relationship; as well as At least one of the first low pass filter cutoff frequency, the first high pass filter cutoff frequency, the second low pass filter cutoff frequency, and / or the second high pass filter cutoff frequency is adjusted to maximize the difference between the first quantitative relationship and the second quantitative relationship.

13. The medical device according to any one of claims 1 to 12, wherein the control circuit is further configured to: determining that the second cardiac event signal is received within an acknowledgement delay time from the first cardiac event signal; and The quantitative relationship is determined in response to receiving the second cardiac event signal within the confirmation delay time.

14. The medical device of claim 13, wherein the control circuit is further configured to schedule pacing pulses by: initiating a pacing interval based on which of the first cardiac event signal or the second cardiac event signal is acknowledged; and The pacing interval is adjusted by one of the confirmation delay time or a time since the second cardiac event signal.

15. The medical device of any one of claims 1 to 15, wherein the control circuit is further configured to determine the quantitative relationship as one of: a ratio of the first characteristic to the second characteristic; a difference between the first characteristic and the second characteristic; the sum of the first characteristic and the second characteristic; or The product of the first feature and the second feature.

16. The medical device according to any one of claims 1 to 15, further comprising a pulse generator configured to generate pacing pulses; The control circuit is further configured as follows: Initiating a pacing escape interval to schedule a pending pacing pulse; initiating an acknowledgement delay in response to receiving the first event signal; determining that the pacing escape interval expires during the confirmation delay period; in response to determining that the pacing escape interval expires during the confirmation delay period, delaying the pending pacing pulse; confirming, based on the quantitative relationship, that the sensed cardiac event signal is one of the first event signal or the second event signal; as well as The pulse generator is controlled to deliver or inhibit the delayed pending pacing pulse according to whether the sensed cardiac event signal is confirmed as the first event signal or the second event signal.

17. The medical device according to any one of claims 1 to 15, further comprising a pulse generator configured to generate pacing pulses; The control circuit is further configured as follows: Initiating a pacing escape interval to schedule a pending pacing pulse; After initiating the pacing escape interval, receiving a next event signal from the sensing circuit after confirming the sensed cardiac event signal; initiating an acknowledgement delay in response to receiving the next event signal; determining that the paced escape interval expires before expiration of the confirmation delay and before another event signal is received from the sensing circuit; as well as In response to the pacing escape interval expiring during the confirmation delay period before receiving another event signal from the sensing circuit, controlling the pulse generator to deliver the scheduled pending pacing pulse upon expiration of the pacing escape interval.

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