Implantable medical device and method for determining His bundle pacing capture

1. An implantable medical device system, comprising:

a sensing circuit configured to sense atrial P-waves from a cardiac electrical signal received via sensing electrodes coupleable to the sensing circuit and produced by a patient's heart;

a therapy delivery circuit configured to generate and deliver His bundle pacing pulses via a His pacing electrode vector coupleable to the therapy delivery circuit; and

a control circuit configured to:

control the therapy delivery circuit to deliver a His bundle pacing pulse;

determine a timing of an atrial P-wave relative to a retrograde conduction time threshold following the delivered His bundle pacing pulse; and

determine a type of capture of the His bundle pacing pulse based on the timing of the atrial P-wave.

2. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detect His bundle capture in response to the time interval being less than a maximum His bundle retrograde conduction time threshold.

3. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detect His bundle loss of capture in response to the time interval being greater than a maximum His bundle retrograde conduction time threshold.

4. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detect ventricular myocardial capture in response to the time interval being greater than a minimum myocardial retrograde conduction time threshold.

5. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detect ventricular myocardial capture in response to the time interval being greater than a minimum myocardial retrograde conduction time threshold and less than a maximum myocardial retrograde conduction time threshold.

6. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by setting a blanking period following the His bundle pacing pulse; and

detect loss of His bundle capture in response to the atrial P-wave being sensed after the blanking period.

7. The system of claim 1 , wherein the control circuit is configured to:

determine the timing of the atrial P-wave by setting a refractory period following the His bundle pacing pulse; and

detect His bundle capture in response to the atrial P-wave being sensed during the refractory period.

8. The system of claim 7 , wherein the control circuit is configured to detect ventricular myocardial capture in response to the atrial P-wave being sensed after the refractory period.

9. The system of claim 1 , wherein the control circuit is further configured to:

determine the timing of the atrial P-wave to be later than a maximum retrograde conduction time limit after the His bundle pacing pulse; and

detect a loss of ventricular capture in response to the timing of the atrial P-wave being later than the maximum retrograde conduction time limit.

10. The system of claim 1 , wherein the control circuit is configured to determine the type of capture as being one of His bundle capture, ventricular myocardial capture, His bundle loss of capture, and loss of ventricular capture.

11. The system of claim 1 , wherein the control circuit is configured to control the therapy delivery circuit to deliver the His bundle pacing pulse asynchronous to atrial events.

12. The system of claim 11 , wherein the control circuit is configured to:

control the therapy delivery circuit to deliver a plurality pacing pulses in an atrial tracking ventricular pacing mode; and

switch to a non-atrial tracking pacing mode for controlling the therapy delivery circuit to deliver the His bundle pacing pulse asynchronous to atrial events.

13. The system of claim 1 , wherein:

the sensing circuit is configured to:

receive a near field His bundle electrical signal via a first sensing electrode vector, and

receive a far field cardiac electrical signal via a second sensing electrode vector different than the first sensing electrode vector; and

the control circuit is configured to determine the type of capture by the His bundle pacing pulse by determining the timing of the atrial P-wave sensed by the sensing circuit and at least one of:

determining a time interval from the His bundle pacing pulse to a QRS signal in the near field His bundle signal; or

determining a feature of a QRS signal in the far field cardiac electrical signal.

14. The system of any of claim 1 , wherein the control circuit is further configured to adjust a ventricular pacing control parameter in response to determining the type of capture.

15. The system of claim 1 , wherein the control circuit is further configured to:

control the therapy delivery circuit to deliver a plurality of His bundle pacing pulses comprising at least two different pacing pulse amplitudes;

determine the type of capture as being His bundle capture following at least one of the plurality of His bundle pacing pulses; and

set a His bundle pacing pulse amplitude based on a lowest one of the at least two different pacing pulse amplitudes for which the His bundle capture is determined.

16. A method, comprising:

sensing atrial P-waves from a cardiac electrical signal produced by a patient's heart and received by a sensing circuit of an implantable medical device;

delivering a His bundle pacing pulse via a His pacing electrode vector;

determining by a control circuit of the implantable medical device a timing of an atrial P-wave relative to a retrograde conduction time threshold following the delivered His bundle pacing pulse; and

determining a type of capture of the His bundle pacing pulse based on the determined timing of the atrial P-wave.

17. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detecting His bundle capture in response to the time interval being less than a maximum His bundle retrograde conduction time threshold.

18. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit; and

detecting His bundle loss of capture in response to the time interval being greater than a maximum His bundle retrograde conduction time threshold.

19. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the atrial P-wave sensed by the sensing circuit;

detecting ventricular myocardial capture in response to the time interval being greater than a minimum myocardial retrograde conduction time threshold.

20. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by determining a time interval from the His bundle pacing pulse to the next atrial P-wave sensed by the sensing circuit; and

detecting ventricular myocardial capture in response to the time interval being greater than a minimum myocardial retrograde conduction time threshold and less than a maximum myocardial retrograde conduction time threshold.

21. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by setting a blanking period that follows the His bundle pacing pulse; and

detecting loss of His bundle capture in response to the next atrial P-wave being sensed after the blanking period.

22. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave by setting a refractory period that follows the His bundle pacing pulse; and

detecting His bundle capture in response to the atrial P-wave being sensed during the refractory period.

23. The method of claim 22 , further comprising detecting ventricular myocardial capture in response to the atrial P-wave being sensed after the refractory period.

24. The method of claim 16 , further comprising:

determining the timing of the atrial P-wave to be later than a maximum retrograde conduction time limit after the His bundle pacing pulse; and

detecting a loss of ventricular capture in response to the timing of the atrial P-wave being later than the maximum retrograde conduction time limit.

25. The method of claim 16 , wherein determining the type of capture comprising determining one of His bundle capture, ventricular myocardial capture, His bundle loss of capture, and loss of ventricular capture.

26. The method of claim 16 , further comprising delivering the His bundle pacing pulse asynchronous to atrial events.

27. The method of claim 26 , further comprising:

delivering a plurality pacing pulses in an atrial tracking ventricular pacing mode; and

switching to a non-atrial tracking pacing mode for controlling the delivery of the His bundle pacing pulse asynchronous to atrial events.

28. The method of claim 16 , further comprising:

receiving a near field His bundle electrical signal via a first sensing electrode vector,

receiving a far field cardiac electrical signal via a second sensing electrode vector different than the first sensing electrode vector; and

determining the type of capture by the His bundle pacing pulse by determining the timing of the atrial P-wave and at least one of:

determining a time interval from the His bundle pacing pulse to a QRS signal in the near field His bundle signal; or

determining a feature of a QRS signal in the far field cardiac electrical signal.

29. The method of claim 16 , further comprising adjusting a ventricular pacing control parameter in response to determining the type of capture.

30. The method of claim 16 , further comprising:

controlling the therapy delivery circuit to deliver a plurality of His bundle pacing pulses comprising at least two different pacing pulse amplitudes;

determining the type of capture as being His bundle capture following at least one of the plurality of His bundle pacing pulses; and

setting a His bundle pacing pulse amplitude based on a lowest one of the at least two different pacing pulse amplitudes for which the His bundle capture is determined.

31. A non-transitory, computer-readable storage medium comprising a set of instructions which, when executed by a controller of an implantable medical device (IMD), cause the IMD to:

sense atrial P-waves from a cardiac electrical signal produced by a patient's heart and received by a sensing circuit of an implantable medical device;

deliver a His bundle pacing pulse to the patient's heart via a His pacing electrode vector;

determine a timing of an atrial P-wave relative to a retrograde conduction time threshold following the delivered His bundle pacing pulse; and

determine a type of capture of the His bundle pacing pulse based on the determined timing of the atrial P-wave.