Reducing false positive lead integrity alerts

1. An implantable medical device comprising:

a sensing circuit configured to receive a cardiac electrical signal and sense cardiac events within the cardiac electrical signal, the cardiac electrical signal received via electrodes carried by a medical electrical lead when the medical electrical lead is coupled to the implantable medical device; and

a control module coupled to the sensing circuit and configured to:

determine a plurality of sensed event intervals, each of the plurality of sensed event intervals being a time interval between two consecutive ones of the sensed cardiac events;

detect a non-sustained tachyarrhythmia (NST) episode based on at least a portion of the sensed event intervals;

determine if the sensed event intervals satisfy an oversensing criteria;

when the sensed event intervals satisfy the oversensing criteria, compare the detected NST episode to non-lead related oversensing criteria;

ignore the NST episode for purposes of determining whether to generate a lead integrity alert when the non-lead related oversensing criteria are satisfied;

use the NST episode as part of an NST component of a lead issue detection criteria when the non-lead related oversensing criteria are not satisfied;

determine that the NST component of the lead issue detection criteria is met; and

generate the lead integrity alert when the NST component of the lead issue detection criteria is met.

2. The device of claim 1 , wherein the control module is configured to determine if the sensed event intervals satisfy the oversensing criteria by determining at least one metric of the sensed event intervals that occur during the detected NST episode and comparing the metric to a threshold, the metric comprising one of a maximum, a minimum, a range, or an average of the sensed event intervals during the NST episode.

3. The device of claim 1 , wherein the control module determines that the NST component of the lead issue detection criteria is met when a threshold number of detected NST episodes are determined to satisfy the oversensing criteria and do not satisfy the non-lead related oversensing criteria.

4. The device of claim 3 , wherein the lead issue detection criteria includes at least one of a lead impedance component and an oversensing component in addition to the NST component, wherein the control module is configured to generate the lead integrity alert when the NST component and at least one of the lead impedance component and the oversensing component are met.

5. The device of claim 4 , wherein the oversensing component comprises a short interval counter and the control module is configured to determine that the oversensing component is met when a value the short interval counter exceeds a threshold value within a predetermined time period.

6. The device of claim 4 , wherein the control module is configured to determine that the lead impedance component of the lead issue detection criteria is met when at least one lead impedance value is outside of an acceptable range of impedances.

7. The device of claim 4 , wherein the control module is configured to determine that the lead impedance component of the lead issue detection criteria is met based on at least one of a long term impedance trend and a short term impedance trend.

8. The device of claim 1 , wherein the control module is configured to compare the detected NST episode to non-lead related oversensing criteria by analyzing a plurality of the sensed events that occur during the detected NST episode to determine if the sensed events during the detected NST episode include a T-wave.

9. The device of claim 1 , wherein the control module is configured to compare the detected NST episode to non-lead related oversensing criteria by determining if the sensed event intervals that occur during the detected NST episode include a double-counted R-wave.

10. The device of claim 1 , wherein the control module is configured to compare the detected NST episode to non-lead related oversensing criteria by:

determining a count of fluctuations of the cardiac electrical signal during at least one sensed event interval that occurs during the NST episode; and

detecting non-lead related oversensing when the count of fluctuations of the signal within the time window reaches a noise threshold.

11. The device of claim 1 , wherein the control module is configured to compare the detected NST episode to non-lead related oversensing criteria by:

determining differences between sample points of the cardiac electrical signal during the detected NST episode;

comparing the magnitude and sign of the differences to non-lead related noise criteria; and

detecting non-lead related oversensing when a threshold number of the differences satisfy the non-lead related noise criteria.

12. The device of claim 1 , wherein the control module is configured to compare the detected NST episode to non-lead related oversensing criteria by:

determining a noise count from the cardiac electrical signal; and

detecting non-lead related oversensing when the noise count reaches a noise threshold during a time interval that includes the detected NST episode and at least one of an event interval immediately preceding the NST episode and an event interval immediately succeeding the NST episode.

13. The device of claim 1 , wherein the control module is further configured to:

increase a counter in response to detecting the NST episode and determining that the oversensing criteria are met;

compare the counter to a lead issue detection threshold; and

compare the detected NST episode to the non-lead related oversensing criteria after the counter reaches the lead issue detection threshold.

14. The device of claim 1 , wherein the control module is further configured to:

compare a preceding NST episode that satisfied the oversensing criteria to the non-lead related oversensing criteria in response to the detected NST episode satisfying the oversensing criteria and not satisfying the non-lead related oversensing criteria; and

maintain a counter at a current value in response to the preceding NST episode satisfying the non-lead related oversensing criteria.

15. The device of claim 1 , wherein the control module is configured to take corrective action in response to the lead issue detection criteria being met.

16. The device of claim 1 , further comprising a telemetry module configured to generate the alert by transmitting a wireless communication signal.

17. A method comprising:

sensing events from the cardiac electrical signal by a sensing module of an implantable medical device, the cardiac electrical signal received via electrodes carried by a medical electrical lead when the medical electrical lead is coupled to the implantable medical device;

determining by a control module of the implantable medical device a plurality of sensed event intervals, each of the plurality of sensed event intervals being a time interval between two consecutive ones of the sensed events;

detecting a non-sustained tachyarrhythmia (NST) episode based on at least a portion of the sensed event intervals;

determining if the sensed event intervals of the NST episode satisfy oversensing criteria;

when the sensed event intervals satisfy the oversensing criteria:

comparing the detected NST episode to non-lead related oversensing criteria;

ignoring the NST episode for purposes of determining whether to generate a lead integrity alert when the non-lead related oversensing criteria are satisfied; and

using the NST episode as part of an NST component of a lead issue detection criteria when the non-lead related oversensing criteria are not satisfied;

determining that the NST component of the lead issue detection criteria is met; and

generating the lead integrity alert when the NST component of the lead issue detection criteria is met.

18. The method of claim 17 , wherein determining if the sensed event intervals satisfy the oversensing criteria comprises determining at least one metric of the sensed event intervals that occur during the detected NST episode and comparing the metric to a threshold, the metric comprising one of a maximum, a minimum, a range, or an average of the sensed event intervals during the NST episode.

19. The method of claim 17 ,

wherein determining that the NST component of the lead issue detection criteria is met comprises determining that the NST component of the lead issue detection criteria is met when a threshold number of detected NST episodes are determined to satisfy the oversensing criteria and to not satisfy the non-lead related oversensing criteria.

20. The method of claim 17 , wherein the lead issue detection criteria includes at least one of a lead impedance component and an oversensing component in addition to the NST component, wherein generating the lead integrity alert comprises generating the lead integrity alert when the NST component and at least one of the lead impedance component and the oversensing component are met.

21. The method of claim 20 , wherein the oversensing component comprises a short interval counter, the method further comprising determining that the oversensing component is met when a value the short interval counter exceeds a threshold value within a predetermined time period.

22. The method of claim 20 , further comprising determining that the lead impedance component of the lead issue detection criteria is met when at least one measured lead impedance value is outside of an acceptable range of impedances.

23. The method of claim 17 , wherein comparing the detected NST episode to non-lead related oversensing criteria comprises analyzing a plurality of the sensed events that occur during the detected NST episode to determine if the sensed events during the detected NST episode include any one of a T-wave and a double-counted R-wave.

24. The method of claim 17 , further comprising:

increasing a counter in response to detecting the NST episode and determining that the oversensing criteria are met;

comparing the counter to a lead issue detection threshold; and

comparing the detected NST episode to the non-lead related oversensing criteria after the counter reaches the lead issue detection threshold.

25. The method of claim 17 , further comprising:

comparing a preceding NST episode that satisfied the lead-related oversensing criteria to the non-lead related oversensing criteria in response to the detected NST episode satisfying the oversensing criteria and not satisfying the non-lead related oversensing criteria; and

maintain an NST counter at a current value in response to the preceding NST episode satisfying the non-lead related oversensing criteria.

26. The method of claim 17 , further comprising taking corrective action in response to the lead issue detection criteria being met.

27. The method of claim 17 , further comprising transmitting a wireless telemetry signal in response to the lead issue detection criteria being met.