Ventricular sensing control in a cardiac pacing system

1. A medical device, comprising:

a sensing circuit configured to:

sense a ventricular electrical signal;

set an R-wave sensing threshold;

receive an atrial event signal;

set a post-atrial time interval in response to the atrial event signal; and

generate an event time signal in response to the ventricular electrical signal being equal to or greater than the R-wave sensing threshold during the post-atrial time interval; and

a control circuit configured to:

determine a count of event time signals generated by the sensing circuit; and

adjust a ventricular sensing control parameter based on the count of event time signals.

2. The medical device of claim 1 , wherein:

the control circuit is configured to adjust the ventricular sensing control parameter by enabling a post-atrial ventricular blanking period.

3. The medical device of claim 2 , wherein:

the sensing circuit is configured to:

set the post-atrial time interval and the post-atrial ventricular blanking period in response to receiving a next atrial event signal, the post-atrial time interval and the post-atrial ventricular blanking period at least partially overlapping;

generate a next event time signal without generating an R-wave sensed event signal in response to the ventricular electrical signal being equal to or greater than the R-wave sensing threshold during an overlapping portion of the post-atrial ventricular blanking period and the post-atrial time interval; and

the control circuit is configured to increase the count of event time intervals in response to the next event time signal.

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

determine a time interval from the atrial event signal to the event time signal;

adjust the ventricular sensing control parameter by adjusting an ending time of a post-atrial ventricular blanking period based on the determined time interval.

5. The medical device of claim 1 , wherein the control circuit is configured to adjust the ventricular sensing control parameter by adjusting a ventricular sensitivity setting used to set the R-wave sensing threshold.

6. The medical device of claim 5 , wherein the control circuit is configured to:

determine at least one amplitude metric from the ventricular electrical signal; and

adjust the ventricular sensitivity setting based on the at least one amplitude metric.

7. The medical device of claim 6 , wherein:

the sensing circuit is configured to:

generate an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold;

determine from the ventricular electrical signal a peak amplitude associated with the R-wave sensed event signal;

the control circuit is configured to:

determine the at least one amplitude metric based at least on the peak amplitude; and

adjust the ventricular sensitivity setting based on the R-wave amplitude metric.

8. The medical device of claim 7 , wherein:

the sensing circuit is configured to determine, from the ventricular electrical signal, an oversense event amplitude associated with the event time signal;

the control circuit is configured to:

determine the at least one amplitude metric by determining an oversense event amplitude metric based at least on the oversense event amplitude; and

adjust the ventricular sensitivity setting based on a comparison of the R-wave amplitude metric to at least one of the oversense event amplitude and the ventricular sensitivity setting.

9. The medical device of claim 1 , wherein the control circuit is configured to:

adjust the count of the event time signals in response to not receiving an event time signal from the sensing circuit during a next post-atrial time interval;

adjust the ventricular sensing control parameter by disabling a post-atrial ventricular blanking period based on the adjusted count of the event time signals.

10. The medical device of claim 1 , wherein:

the sensing circuit is further configured to:

generate an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold; and

sense an atrial electrical signal;

the control circuit is configured to:

detect atrial tachyarrhythmia from the atrial electrical signal;

determine that the R-wave sensed event signal is generated by the sensing circuit during a post-atrial time interval;

increase a count of oversensing evidence in response to the R-wave sensed event signal being generated during the post-atrial time interval; and

enable a post-atrial ventricular blanking period in response to the increased count of oversensing evidence.

11. The medical device of claim 10 , wherein the control circuit is configured to:

determine an atrial event interval between two consecutive atrial event signals;

set oversensing evidence criteria based on a ratio of the post-atrial time interval to the atrial event interval;

compare the count of oversensing evidence to the oversensing criteria; and

enable the post-atrial ventricular blanking period in response to the increased count of oversensing evidence meeting the oversensing evidence criteria.

12. The medical device of claim 1 , wherein:

the sensing circuit is further configured to:

generate an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold; and

sense an atrial electrical signal;

the control circuit is configured to:

detect atrial tachyarrhythmia from the atrial electrical signal;

temporarily disable a post-atrial ventricular blanking period in response to detecting the atrial tachyarrhythmia;

determine that an R-wave sensed event signal is generated by the sensing circuit outside the post-atrial time interval when the post-atrial ventricular blanking period is temporarily disabled; and

disable the post-atrial ventricular blanking period during the detected atrial tachyarrhythmia in response to at least the R-wave sensed event signal being generated outside the post-atrial time interval when the post-atrial ventricular blanking period is disabled.

13. The medical device of claim 1 , further comprising:

a therapy delivery circuit configured to generate atrial pacing pulses;

wherein the sensing circuit is further configured to:

sense an atrial electrical signal; and

generate a P-wave sensed event signal in response to the atrial electrical signal crossing a P-wave sensing threshold,

receive the atrial event signal associated with one of an atrial pacing pulse generated by the therapy delivery circuit or a P-wave sensed event signal generated by the sensing circuit;

set the post-atrial time interval to a first time duration in response to receiving the atrial event signal associated with a P-wave sensed event signal; and

set the post-atrial time interval to a second time duration greater than the first time duration in response to receiving the atrial event signal associated with an atrial pacing pulse.

14. The medical device of claim 1 , wherein:

the control circuit is configured to adjust the ventricular sensing control parameter by setting a safety pace interval in response to receiving an atrial event signal;

the sensing circuit is configured to generate an R-wave sensed event signal during the safety pace interval in response to the ventricular electrical signal crossing the R-wave sensing threshold during the safety pace interval;

the medical device further comprising a therapy delivery circuit configured to generate a ventricular pacing pulse upon expiration of the safety pace interval in response to the R-wave sensed event signal being generated during the safety pace interval.

15. The medical device of claim 1 , wherein the sensing circuit is configured to:

set a post-atrial ventricular blanking period in response to the atrial event signal; and

generate an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold during the post-atrial time interval and outside the post-atrial ventricular blanking period.

16. The device of claim 1 , wherein the control circuit is further configured to:

compare the count of event time signals to first oversensing criteria when a post-atrial ventricular blanking period is enabled;

compare the count of event time signals to second oversensing criteria different than the first oversensing criteria when the post-atrial ventricular blanking period is disabled; and

adjust the ventricular sensing control parameter in response to the count of event time signals meeting one of the first oversensing criteria or the second oversensing criteria.

17. A method, comprising:

sensing a ventricular electrical signal;

setting an R-wave sensing threshold;

receiving an atrial event signal;

setting a post-atrial time interval in response to receiving the atrial event signal;

generating an event time signal in response to the ventricular electrical signal being equal to or greater than the R-wave sensing threshold during the post-atrial time interval;

determining a count of event time signals in response to the generated event time signal; and

adjusting a ventricular sensing control parameter based on the count of event time signals.

18. The method of claim 17 , comprising:

adjusting the ventricular sensing control parameter by enabling a post-atrial ventricular blanking period.

19. The method of claim 18 , comprising:

setting the post-atrial time interval and the post-atrial ventricular blanking period in response to receiving a next atrial event signal, the post-atrial time interval and the post-atrial ventricular blanking period at least partially overlapping;

generating a next event time signal without generating an R-wave sensed event signal in response to the ventricular electrical signal being equal to or greater than the R-wave sensing threshold during an overlapping portion of the post-atrial ventricular blanking period and the post-atrial time interval; and

increasing the count of event time intervals in response to the next event time signal.

20. The method of claim 17 , further comprising:

determining a time interval from the atrial event signal to the event time signal;

adjust the ventricular sensing control parameter by adjusting an ending time of a post-atrial ventricular blanking period based on the determined time interval.

21. The method of claim 17 , wherein adjusting the ventricular sensing control parameter comprises adjusting a ventricular sensitivity setting used to set the R-wave sensing threshold.

22. The method of claim 21 , comprising:

determining at least one amplitude metric from the ventricular electrical signal; and

adjusting the ventricular sensitivity setting based on the at least one amplitude metric.

23. The method of claim 22 , comprising:

generating an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold;

determining, from the ventricular electrical signal, a peak amplitude associated with the R-wave sensed event signal;

determining the at least one amplitude metric based at least on the peak amplitude; and

adjust the ventricular sensitivity setting based on the R-wave amplitude metric.

24. The method of claim 23 , comprising:

determining, from the ventricular electrical signal, an oversense event amplitude associated with the event time signal;

determining the at least one amplitude metric by determining an oversense event amplitude metric based at least on the oversense event amplitude; and

adjusting the ventricular sensitivity setting based on a comparison of the R-wave amplitude metric to at least one of the oversense event amplitude and the ventricular sensitivity setting.

25. The method of claim 17 , comprising:

adjusting the count of the event time signals in response to not receiving an event time signal from the sensing circuit during a next post-atrial time interval;

adjusting the ventricular sensing control parameter by disabling a post-atrial ventricular blanking period based on the adjusted count of the event time signals.

26. The method of claim 17 , further comprising:

generating an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold;

sensing an atrial electrical signal;

detecting atrial tachyarrhythmia from the atrial electrical signal;

determining that the R-wave sensed event signal is generated by the sensing circuit during a post-atrial time interval;

increasing a count of oversensing evidence in response to the R-wave sensed event signal being generated during the post-atrial time interval; and

enable a post-atrial ventricular blanking period in response to the increased count of oversensing evidence.

27. The method of claim 26 , further comprising:

determining an atrial event interval between two consecutive atrial event signals;

set oversensing evidence criteria based on a ratio of the post-atrial time interval to the atrial event interval;

comparing the count of oversensing evidence to the oversensing criteria; and

enabling a post-atrial ventricular blanking period in response to the increased count of oversensing evidence meeting the oversensing evidence criteria.

28. The method of claim 17 , further comprising:

generating an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold;

sensing an atrial electrical signal;

detecting atrial tachyarrhythmia from the atrial electrical signal;

temporarily disabling a post-atrial ventricular blanking period in response to detecting the atrial tachyarrhythmia;

determining that the R-wave sensed event signal is generated by the sensing circuit outside the post-atrial time interval when the post-atrial ventricular blanking period is temporarily disabled; and

disabling the post-atrial ventricular blanking period during the detected atrial tachyarrhythmia in response to at least the R-wave sensed event signal being generated outside the post-atrial time interval when the post-atrial ventricular blanking period is disabled.

29. The method of claim 17 , comprising:

generating atrial pacing pulses;

sensing an atrial electrical signal;

generating a P-wave sensed event signal in response to the atrial electrical signal crossing a P-wave sensing threshold,

receiving the atrial event signal associated with one of an atrial pacing pulse or a P-wave sensed event signal;

setting the post-atrial time interval to a first time duration in response to receiving the atrial event signal associated with a P-wave sensed event signal; and

setting the post-atrial time interval to a second time duration greater than the first time duration in response to receiving the atrial event signal associated with an atrial pacing pulse.

30. The method of claim 17 , comprising:

adjusting the ventricular sensing control parameter by setting a safety pace interval in response to the atrial event signal;

generating an R-wave sensed event signal during the safety pace interval in response to the ventricular electrical signal crossing the R-wave sensing threshold during the safety pace interval;

generating a ventricular pacing pulse upon expiration of the safety pace interval in response to the R-wave sensed event signal being generated during the safety pace interval.

31. The method of claim 17 , further comprising:

setting a post-atrial ventricular blanking period in response to the atrial event signal; and

generating an R-wave sensed event signal in response to the ventricular electrical signal crossing the R-wave sensing threshold during the post-atrial time interval and outside the post-atrial ventricular blanking period.

32. The method of claim 17 , comprising:

comparing the count of event time signals to first oversensing criteria when a post-atrial ventricular blanking period is enabled;

compare the count of event time signals to second oversensing criteria different than the first oversensing criteria when the post-atrial ventricular blanking period is disabled; and

adjust the ventricular sensing control parameter in response to the count of event time signals meeting one of the first oversensing criteria or the second oversensing criteria.

33. A non-transitory, computer-readable storage medium comprising a set of instructions which, when executed by a control circuit of a medical device cause the medical device to:

sense a ventricular electrical signal;

set an R-wave sensing threshold;

receive an atrial event signal;

set a post-atrial time interval in response to receiving the atrial event signal;

generate an event time signal in response to the ventricular electrical signal being equal to or greater than the R-wave sensing threshold during the post-atrial time interval;

determine a count of event time signals in response to the generated event time signal; and

adjust a ventricular sensing control parameter based on the count of event time signals.