Episode classifier algorithm

• US 8,437,840 B2
• Filed: 09/26/2011
• Issued: 05/07/2013
• Est. Priority Date: 09/26/2011
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Patel, Amisha S., Gunderson, Bruce D., Brown, Mark L.
• Primary Examiner(s): Gedeon, Brian T
• Application Number:
  US13/245,632
• Publication Number:
  US 20130079651A1
• Time in Patent Office: 589 Days
• Field of Search: 600/508, 600/509, 600515-519, 607/14, 607/18
• US Class Current: 600/515
• CPC Class Codes: A61B 5/35 by template matching
• 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 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential

Abstract

The present disclosure is directed to the classification of cardiac episodes using an algorithm. In various examples, an episode classification algorithm evaluates electrogram signal data collected by an implantable medical device. The episode classification algorithm may classify may include a sinus template and a comparison of the electrogram signal to the sinus template. Possible classifications of the cardiac episode may include, for example, unknown, inappropriate, appropriate, supraventricular tachycardia, ventricular tachycardia, ventricular fibrillation or ventricular over-sensing.

Claims

1. A method comprising:

collecting a sinus template from a first ventricular EGM signal,

wherein the sinus template comprises a portion of the first ventricular EGM signal including at least one ventricular beat, and

wherein collecting the sinus template comprises collecting the sinus template from a portion of the ventricular EGM that occurred when the ventricular EGM signal and an atrial EGM signal indicated a one to one ratio of atrial events to ventricular events, a P-R interval greater than a first predetermined threshold, an R-R interval greater than a second predetermined threshold, and two consecutive R-R intervals within a predetermined range;

comparing the sinus template to a second ventricular EGM signal; and

determining, based on the comparison, whether the morphology of the second ventricular EGM signal matches the sinus template.

2. The method of claim 1, wherein the sinus template comprises a portion of the first ventricular EGM signal adjacent and subsequent to an anti-tachycardia pacing period.

3. The method of claim 2, wherein collecting the sinus template comprises collecting the sinus template when the portion of the first ventricular EGM signal adjacent and subsequent to the anti-tachycardia pacing period comprises an R-R interval that has increased by at least about 100 milliseconds (ms) from a pre anti-tachycardia pacing R-R interval.

4. The method of claim 1, wherein the sinus template comprises a portion of the first ventricular EGM signal prior and adjacent to onset of a cardiac arrhythmia episode.

5. The method of claim 1, further comprising preforming real-time diagnosis of cardiac arrhythmia based on the sinus template by an implantable medical device.

6. The method of claim 1, further including determining whether a cardiac arrhythmia diagnosis previously made by an implantable medical device was correct based on the sinus template.

7. The method of claim 1, further comprising:

determining whether a morphology of the second ventricular EGM signal and a morphology of the sinus template match; and

classifying an episode including the second ventricular EGM signal as a supraventricular tachycardia in response to determining that the morphologies match.

8. The method of claim 7, wherein determining whether the morphologies match comprises

comparing each of a plurality of intervals of the second ventricular EGM signal to the sinus template;

determining, based on the comparison, a level of correlation between each of the plurality of intervals and the sinus template;

classifying each of the plurality of intervals as matched or unmatched based on a predetermined threshold for level of correlation;

comparing a percentage of intervals classified as matched to a predetermined matching percentage threshold, and

determining that the morphologies match in response to the percentage of intervals classified as matched being above the predetermined matching percentage threshold.

9. The method of claim 1, further comprising comparing an episode comprising the second ventricular EGM signal to a VT template, and:

in response to a match between the episode and the VT template classifying the episode as ventricular tachycardia or ventricular fibrillation; and

in response to no match between the episode and the VT template, comparing the episode to the sinus template.

10. The method of claim 1, wherein the first predetermined threshold is about 80 ms, the second predetermined threshold is about 500 ms, and the predetermined range is about 50 ms.

11. A device comprising:

a processor configured to

collect a sinus template from a first ventricular EGM signal,

wherein the sinus template comprises a portion of the first ventricular EGM signal including at least one ventricular beat, and

wherein collecting the sinus template comprises collecting the sinus template from a portion of the ventricular EGM that occurred when the ventricular EGM signal and an atrial EGM signal indicated a one to one ratio of atrial events to ventricular events, a P-R interval greater than a first predetermined threshold, an R-R interval greater than a second predetermined threshold; and

two consecutive R-R intervals within a predetermined range;

compare the sinus template to a second ventricular EGM signal, and

determine, based on the comparison, whether the morphology of the second ventricular EGM signal matches the sinus template.

12. The device of claim 11, further including a sensing module configured to receive the EGM signal from electrodes coupled to the device.

13. The device of claim 11, wherein the sinus template comprises a portion of the first ventricular EGM signal adjacent and subsequent to an anti-tachycardia pacing period.

14. The device of claim 13, wherein collecting the sinus template comprises collecting the sinus template when the portion of the first ventricular EGM signal adjacent and subsequent to the anti-tachycardia pacing period comprises an R-R interval that has increased by at least about 100 ms from a pre anti-tachycardia pacing R-R interval.

15. The device of claim 11, wherein the device is an implantable medical device and the processor is further configured to preform real time diagnosis of cardiac arrhythmia based on the sinus template.

16. The device of claim 11, wherein the processor is further configured to determine whether a cardiac arrhythmia diagnosis previously made by the implantable medical device was correct based on the comparison of the second ventricular EGM signal to the sinus template.

17. The device of claim 11, wherein the processor is further configured to

determine whether a morphology of the second ventricular EGM signal and a morphology of the sinus template match;

and

classify an episode including the second ventricular EGM signal as a supraventricular tachycardia in response to determining that the morphologies match.

18. The device of claim 17, wherein the processor if further configured to make the determination whether the morphologies match by

comparing each of a plurality of intervals of the second ventricular EGM signal to the sinus template;

determining, based on the comparison, a level of correlation between each of the plurality of intervals and the sinus template;

classifying each of the plurality of intervals as matched or unmatched based on a predetermined threshold for level of correlation;

comparing a percentage of intervals classified as matched to a predetermined matching percentage threshold, and

determining that the morphologies match in response to the percentage of intervals classified as matched being above the predetermined matching percentage threshold.

19. The device of claim 11, wherein the processor if further configured to compare an episode comprising the second EGM signal to a VT template, and

in response to a match between the episode and the VT template classify the episode as ventricular tachycardia or ventricular fibrillation;

and

in response to no match between the episode and the VT template, compare the episode to the sinus template.

20. The device of claim 11, wherein the first predetermined threshold is about 80 ms, the second predetermined threshold is about 500 ms, and the predetermined range is about 50 ms.

21. A device comprising:

means for collecting a sinus template from an EGM signal;

the sinus template collected when the EGM signal has a one to one ratio of atrial events to ventricular events, a P-R interval greater than 80 milliseconds (ms), an R-R interval greater than 500 ms; and

two consecutive R-R intervals within 50 ms of each other;

means for comparing the sinus ventricular beat template to a second EGM signal, and

means for determining, based on the comparison, whether the morphology of the second EGM signal matches the sinus template.

22. A computer-readable medium containing instructions, the instructions causing a programmable processor to:

collect a sinus template from a first ventricular EGM signal,

wherein the sinus template comprises a portion of the first ventricular EGM signal including at least one ventricular beat, and

wherein collecting the sinus template comprises collecting the sinus template from a portion of the ventricular EGM that occurred when the ventricular EGM signal and an atrial EGM signal indicated a one to one ratio of atrial events to ventricular events, a P-R interval greater than a first predetermined threshold, an R-R interval greater than a second predetermined threshold; and

two consecutive R-R intervals within a predetermined range;

compare the sinus template to a second ventricular EGM signal, and

determine, based on the comparison, whether the morphology of the second ventricular EGM signal matches the sinus template.