Detection of tachyarrhytmia termination

• US 20040171959A1
• Filed: 02/27/2003
• Published: 09/02/2004
• Est. Priority Date: 02/27/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Stadler, Robert W., Warman, Eduardo N., Ericksen, James H., Holbrook, Reece W.
• Granted Patent: US 7,103,404 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

Determining termination of an identified tachyarrhythmia episode may involve analysis of a relative decrease in tachyarrhythmia rate, a normalization of electrogram morphology criteria, or both. An implanted medical device may obtain a tachyarrhythmia rate and a morphology of a cardiac waveform. The device may compare the tachyarrhythmia rate to a threshold tachyarrhythmia rate and the morphology to a template morphology, and classify the heart beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate is less than the threshold tachyarrhythmia rate, the morphology categorizes as normal, or both. For arrhythmias with no therapy delivered, observation of arrhythmia behavior at the point of termination may lead to improved classification. In addition, observation of a relative decrease in tachyarrhythmia rate immediately after therapy application can lead to application of slower but more specific criteria for redetection. Also, delivery of cardioversion shocks can be aborted upon tachyarrhythmia termination.

Claims

1. A method comprising:

obtaining a cardiac tachyarrhythmia rate associated with a heart beat;

obtaining a morphology of a cardiac waveform associated with the heart beat; and

determining whether a detected tachyarrhythmia episode has terminated based on the tachyarrhythmia rate and the morphology.

2. The method of claim 1, further comprising:

classifying the beat as indicating termination of the tachyarrhythmia episode; and

determining that the detected tachyarrhythmia episode has terminated when a number of beats classified as indicating termination of the tachyarrhythmia episode exceed a threshold.

3. The method of claim 2, wherein the threshold includes a number of consecutive beats.

4. The method of claim 2, wherein the threshold includes a portion of consecutive beats.

5. The method of claim 2, further comprising:

comparing the tachyarrhythmia rate with a threshold tachyarrhythmia rate;

comparing the morphology of the cardiac waveform with a template morphology of a cardiac waveform; and

classifying the beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate falls below the threshold tachyarrhythmia rate and the morphology categorizes as normal.

6. The method of claim 5, further comprising obtaining the template morphology during a sinus rhythm.

7. The method of claim 5, further comprising:

measuring a metric of the tachyarrhythmia rate of the tachyarrhythmia episode; and

calculating the threshold tachyarrhythmia rate as a function of the metric of the tachyarrhythmia rate.

8. The method of claim 7, wherein calculating the threshold tachyarrhythmia rate as a function of the metric of the tachyarrhythmia rate includes subtracting an offset from the metric of the rate of the tachyarrhythmia episode to calculate the threshold tachyarrhythmia rate.

9. The method of claim 7, wherein the metric of the tachyarrhythmia rate includes one of a median of the tachyarrhythmia rate, a mean of the tachyarrhythmia rate, a maximum of the tachyarrhythmia rate and a minimum of the tachyarrhythmia rate.

10. The method of claim 2, further comprising:

comparing the tachyarrhythmia rate with a range; and

classifying the beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate falls below the range.

11. The method of claim 10, further comprising:

comparing the morphology with a template morphology when the tachyarrhythmia rate is within the range; and

classifying the beat as indicating termination of the tachyarrhythmia episode when the morphology categorizes as normal.

12. The method of claim 1, further comprising aborting delivery of therapy upon determining that the detected tachyarrhythmia episode has terminated.

13. The method of claim 1, further comprising classifying the arrhythmia type of the tachyarrhythmia episode based on information associated with the tachyarrhythmia episode at termination.

14. The method of claim 13, further comprising:

identifying the tachyarrhythmia episode to have a 1;

1 atrial to ventricular conduction rate;

identifying a rapid deceleration in the heart rate at termination of the tachyarrhythmia episode;

determining whether a last depolarization prior to the deceleration is a ventricular depolarization; and

classifying the arrhythmia type of the tachyarrhythmia episode as a supraventricular tachycardia when the last depolarization prior to the deceleration is a ventricular depolarization.

15. The method of claim 14, further comprising classifying the arrhythmia type of the tachyarrhythmia episode as a ventricular tachycardia when the last depolarization prior to the deceleration is not a ventricular depolarization.

16. The method of claim 1, further comprising:

applying a therapy to a patient;

redetecting the tachyarrhythmia episode after applying the therapy; and

reapplying the therapy to the patient when the tachyarrhythmia episode is redetected.

17. The method of claim 16, wherein redetecting the tachyarrhythmia episode includes:

determining that a tachyarrhythmia rate of a successive heart beat does not decrease;

comparing the tachyarrhythmia rate of the successive heart beat to a threshold tachyarrhythmia rate; and

redetecting the tachyarrhythmia episode when the tachyarrhythmia rate of the successive heart beat exceeds the threshold.

18. The method of claim 16, wherein redetecting the tachyarrhythmia episode includes:

determining that a tachyarrhythmia rate of a successive heart beat decreases;

comparing the tachyarrhythmia rate of the successive heart beat to a threshold tachyarrhythmia rate;

comparing a morphology of the successive heart beat to a template morphology; and

redetecting the tachyarrhythmia episode when the tachyarrhythmia rate of the successive heart beat exceeds the threshold and the morphology of the successive heart beat categorizes as normal.

19. The method of claim 1, wherein obtaining a tachyarrhythmia rate associated with a heart beat includes obtaining an R-R interval associated with the heart beat.

20. A device comprising:

a first detector to detect a tachyarrhythmia rate associated with a heart beat;

a second detector to detect a morphology of a cardiac waveform associated with the heart beat; and

a processor to determine whether a detected tachyarrhythmia episode has terminated based on the tachyarrhythmia rate and the morphology.

21. The device of claim 20, wherein the processor classifies the beat as indicating termination of the tachyarrhythmia episode and determines that the detected tachyarrhythmia episode has terminated when a number of beats classified as indicating termination of the tachyarrhythmia episode exceed a threshold.

22. The device of claim 21, wherein the threshold includes a number of consecutive beats.

23. The device of claim 21, wherein the threshold includes a portion of consecutive beats.

24. The device of claim 21, wherein the processor compares the tachyarrhythmia rate with a threshold tachyarrhythmia rate, compares the morphology of the cardiac waveform with a template morphology of a cardiac waveform, and classifies the beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate is less than the threshold tachyarrhythmia rate and the morphology categorizes as normal.

25. The device of claim 24, wherein the processor measures a metric of the tachyarrhythmia rate of the tachyarrhythmia episode and subtracts from the metric of the tachyarrhythmia rate an offset to obtain the threshold tachyarrhythmia rate.

26. The device of claim 24, wherein the metric of the tachyarrhythmia rate includes one of a median of the tachyarrhythmia rate, a mean of the tachyarrhythmia rate, a maximum of the tachyarrhythmia rate and a minimum of the tachyarrhythmia rate.

27. The device of claim 24, wherein the processor compares the tachyarrhythmia rate with a range, and classifies the beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate falls below the range.

28. The device of claim 27, wherein the processor compares the morphology with a template morphology when the tachyarrhythmia rate is within the range and classifies the beat as indicating termination of the tachyarrhythmia episode when the morphology categorizes as normal.

29. The device of claim 21, wherein the processor classifies the arrhythmia type of the tachyarrhythmia episode based on information associated with the tachyarrhythmia episode at termination.

30. The device of claim 20, wherein the processor determines whether the tachyarrhythmia episode has terminated when a tachyarrhythmia rate of a successive beat decreases in response to delivered therapy and aborts the therapy when the tachyarrhythmia episode has terminated.

31. A method comprising:

obtaining a morphology of a cardiac waveform associated with a heart beat; and

determining whether a detected tachyarrhythmia episode has terminated based on the morphology.

32. The method of claim 31, further comprising comparing the obtained morphology with a template morphology of a cardiac waveform of a heart beat during sinus rhythm.

33. The method of claim 32, further comprising:

classifying the beat as indicating termination of the tachyarrhythmia episode when the morphology categorizes as normal; and

determining that the detected tachyarrhythmia episode has terminated when a number of beats classified as indicating termination of the tachyarrhythmia episode exceed a threshold.

34. The method of claim 33, wherein categorizing the morphology as normal includes:

comparing at least one characteristic of the waveforms to obtain a score; and

categorizing the morphology as normal when the score exceeds a threshold.

35. The method of claim 34, wherein the characteristic includes at least one of an amplitude of the peaks, a width of the peaks, and a polarity of the peaks.

36. A method comprising:

measuring a metric of a rate of a tachyarrhythmia episode of the tachyarrhythmia episode;

calculating a relative threshold tachyarrhythmia rate as a function of the metric of the rate of the tachyarrhythmia episode;

comparing a tachyarrhythmia rate associated with a heart beat with the relative threshold tachyarrhythmia rate; and

determining whether the detected tachyarrhythmia episode has terminated based on the comparison.

37. The method of claim 36, further comprising:

classifying the beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate falls below the threshold tachyarrhythmia rate; and

determining that the detected tachyarrhythmia episode has terminated when a number of beats classified as indicating termination of the tachyarrhythmia episode exceed a threshold.

38. The method of claim 36, wherein calculating the threshold tachyarrhythmia rate as a function of the metric of the tachyarrhythmia rate includes subtracting an offset from the metric of the rate of the tachyarrhythmia episode to calculate the threshold tachyarrhythmia rate.

39. The method of claim 36, wherein the metric of the tachyarrhythmia rate includes one of a median of the tachyarrhythmia rate, a mean of the tachyarrhythmia rate, a maximum of the tachyarrhythmia rate and a minimum of the tachyarrhythmia rate.

40. The method of claim 36, further comprising obtaining a tachyarrhythmia rate associated with a heart beat.

41. The method of claim 40, wherein obtaining a tachyarrhythmia rate associated with a heart beat includes obtaining an R-R interval associated with the heart beat.

42. The method of claim 36, further comprising:

determining termination of the tachyarrhythmia episode; and

classifying the arrhythmia type of the tachyarrhythmia episode based on information associated with the tachyarrhythmia episode at termination.