Method and apparatus for adjusting a threshold during atrial arrhythmia episode detection in an implantable medical device

• US 9,936,890 B2
• Filed: 10/29/2015
• Issued: 04/10/2018
• Est. Priority Date: 02/18/2015
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sarkar, Shantanu, Hansen, Daniel L, Neitzell, Grant A, Reiland, Jerry D, Wyszynski, Ryan
• Primary Examiner(s): Holmes, Rex R
• Application Number:
  US14/926,419
• Publication Number:
  US 20160235317A1
• Time in Patent Office: 894 Days
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/3624 occurring in the atrium, i.e. atrial tachycardia
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential
• CPC Class Codes: A61N 1/36592 controlled by the heart rate variability
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

An implantable medical device and method for determining an atrial arrhythmia event that includes a cardiac sensing device comprising a housing having circuitry positioned therein, a plurality of electrodes electrically coupled to the circuitry to sense a cardiac signal, and a processor configured to generate an initial detection of an atrial arrhythmia event in response to an atrial arrhythmia threshold, determine whether a P-wave occurs during the initial detection, determine an adaptive threshold in response to the P-wave being detected, adjust the atrial arrhythmia threshold in response to the adaptive threshold, and generate a subsequent initial detection of an atrial arrhythmia event using the adjusted atrial arrhythmia threshold.

Claims

1. An implantable medical device for determining an atrial arrhythmia event,

comprising:

a cardiac sensing device comprising a housing having circuitry positioned therein;

a plurality of electrodes electrically coupled to the circuitry to sense a cardiac signal; and

a processor configured to generate an initial detection of an atrial arrhythmia event in response to an atrial arrhythmia threshold, determine whether a P-wave is detected during the initial detection, identify the initial detection as a false positive detection in response to a P-wave being detected, determine an adaptive threshold in response to the P-wave being detected, adjust the atrial arrhythmia threshold in response to the adaptive threshold, and generate a subsequent detection of an atrial arrhythmia event using the adjusted atrial arrhythmia threshold.

2. The implantable medical device of claim 1, wherein the atrial arrhythmia event comprises an atrial fibrillation event.

3. The implantable medical device of claim 1, wherein the processor is further configured to increment an adjustment count in response to the initial detection being identified as a false positive detection, and determine the adaptive threshold in response to the adjustment count.

4. The implantable medical device of claim 3, wherein the processor is further configured to set the adaptive threshold equal to a ratio of the adjustment count and a tuning factor corresponding to a desired level of aggressiveness for rejecting inappropriate determinations of the atrial arrhythmia event.

5. The implantable medical device of claim 3, wherein the processor is configured to determine whether the adaptive threshold is greater than a maximum adaptive threshold, and add the adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold not being greater than the maximum adaptive threshold.

6. The implantable medical device of claim 5, wherein the processor is configured to set the adaptive threshold equal to the maximum adaptive threshold and add the maximum adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold being greater than the maximum adaptive threshold.

7. The implantable medical device of claim 1, wherein the processor is configured to confirm the initial determination of the atrial arrhythmia event in response to a P-wave not being detected, determine whether a duration of the detected atrial arrhythmia event is greater than a duration threshold, and set the adjustment count to zero in response to the duration of the detected atrial arrhythmia event being greater than the duration threshold.

8. The implantable medical device of claim 7, wherein the processor is configured to determine an RR-interval variation associated with the sensed cardiac signal, determine an atrial arrhythmia score in response the RR-interval variation, determine whether the score is greater than the atrial arrhythmia threshold, increment a normal sinus count, determine whether the normal sinus count is greater than a normal sinus count threshold, and set the adjustment count to zero in response to the normal sinus count being greater than the normal sinus count threshold.

9. The implantable medical device of claim 8, wherein the processor is further configured to increment an adjustment count in response to the initial detection being identified as a false positive detection, and determine the adaptive threshold in response to the adjustment count.

10. The implantable medical device of claim 9, wherein the processor is further configured to set the adaptive threshold equal to a ratio of the adjustment count and a tuning factor corresponding to a desired level of aggressiveness for rejecting inappropriate determinations of the atrial arrhythmia event.

11. The implantable medical device of claim 10, wherein the processor is configured to determine whether the adaptive threshold is greater than a maximum adaptive threshold, and add the adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold not being greater than the maximum adaptive threshold.

12. The implantable medical device of claim 11, wherein the processor is configured to set the adaptive threshold equal to the maximum adaptive threshold and add the maximum adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold being greater than the maximum adaptive threshold.

13. The implantable medical device of claim 12, wherein the atrial arrhythmia event comprises an atrial fibrillation event.

14. The implantable medical device of claim 1, wherein the atrial arrhythmia event comprises an atrial tachycardia event.

15. A method of determining an atrial arrhythmia event in an implantable medical device, comprising:

sensing a cardiac signal;

generating an initial detection of an atrial arrhythmia event in response to an atrial arrhythmia threshold;

determining whether a P-wave is detected during the initial detection;

identifying the initial detection as a false positive detection in response to a P-wave being detected;

determining an adaptive threshold in response to the P-wave being detected;

adjusting the atrial arrhythmia threshold in response to the adaptive threshold; and

generating a subsequent detection of an atrial arrhythmia event using the adjusted atrial arrhythmia threshold.

16. The method of claim 15, wherein the atrial arrhythmia event comprises an atrial fibrillation event.

17. The method of claim 15, further comprising:

incrementing an adjustment count in response to the initial detection being identified as a false positive detection; and

determining the adaptive threshold in response to the adjustment count.

18. The method of claim 17, further comprising setting the adaptive threshold equal to a ratio of the adjustment count and a tuning factor corresponding to a desired level of aggressiveness for rejecting inappropriate determinations of the atrial arrhythmia event.

19. The method of claim 17, further comprising:

determining whether the adaptive threshold is greater than a maximum adaptive threshold; and

adding the adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold not being greater than the maximum adaptive threshold.

20. The method of claim 19, further comprising:

setting the adaptive threshold equal to the maximum adaptive threshold; and

adding the maximum adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold being greater than the maximum adaptive threshold.

21. The method of claim 15, further comprising:

confirming the initial determination of the atrial arrhythmia event in response to a P-wave not being detected;

determining whether a duration of the detected atrial arrhythmia event is greater than a duration threshold; and

setting the adjustment count to zero in response to the duration of the detected atrial arrhythmia event being greater than the duration threshold.

22. The method of claim 15, further comprising:

determining an RR-interval variation associated with the sensed cardiac signal;

determining an atrial arrhythmia score in response the RR-interval variation;

determining whether the score is greater than the atrial arrhythmia threshold;

incrementing a normal sinus count;

determining whether the normal sinus count is greater than a normal sinus count threshold; and

setting the adjustment count to zero in response to the normal sinus count being greater than the normal sinus count threshold.

23. The method of claim 22, further comprising:

incrementing an adjustment count in response to the initial detection being identified as a false positive detection; and

determining the adaptive threshold in response to the adjustment count.

24. The method of claim 23, further comprising setting the adaptive threshold equal to a ratio of the adjustment count and a tuning factor corresponding to a desired level of aggressiveness for rejecting inappropriate determinations of the atrial arrhythmia event.

25. The method of claim 24, further comprising:

determining whether the adaptive threshold is greater than a maximum adaptive threshold; and

adding the adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold not being greater than the maximum adaptive threshold.

26. The method of claim 25, further comprising:

setting the adaptive threshold equal to the maximum adaptive threshold; and

adding the maximum adaptive threshold to the atrial arrhythmia threshold in response to the adaptive threshold being greater than the maximum adaptive threshold.

27. The method of claim 26, wherein the atrial arrhythmia event comprises an atrial fibrillation event.

28. The method of claim 15, wherein the atrial arrhythmia event comprises an atrial tachycardia event.