Method and apparatus for verifying discriminating of tachycardia events in a medical device having dual sensing vectors

• US 10,226,639 B2
• Filed: 05/31/2016
• Issued: 03/12/2019
• Est. Priority Date: 04/17/2014
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): Patel, Natasha
• Application Number:
  US15/168,590
• Publication Number:
  US 20160346558A1
• Time in Patent Office: 1,015 Days
• CPC Class Codes: A61B 5/283 Invasive
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

A method and medical device for detecting a cardiac event that includes sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector sensing a first interval and a second sensing vector simultaneously sensing a second, determining, for each of the first interval and the second interval, whether each beat of the plurality of beats is one of a match beat and a non-match beat, determining whether each beat of the plurality of beats is one of a high confidence beat and a low confidence beat, determining, for each of the first interval and the second interval, the number of beats determined to be both a non-match beat and a high confidence beat is greater than a non-match threshold, and determining whether to deliver therapy for the cardiac event in response to identifying of each of the first interval and the second interval as being one of shockable and not shockable.

Claims

1. A method for detecting a cardiac event in a medical device, the method comprising:

obtaining a first cardiac signal sensed via a first set of electrodes forming a first sensing vector;

obtaining a second cardiac signal sensed via a second set of electrodes forming a second sensing vector;

identifying a plurality of beats within a first segment of the first cardiac signal and a second segment of the second cardiac signal, the second segment being sensed simultaneously with the first segment;

analyzing each of the plurality of beats of the first segment and the second segment, wherein the analyzing includes;

determining, for each of the plurality of beats, whether the respective beat matches a template beat;

classifying beats of the plurality of beats that match the template beat as match beats and beats of the plurality of beats that do not match the template beat as non-match beats;

determining, for each of the plurality of beats, individual pulses associated with the respective beats; and

classifying each of the plurality of beats as one of a high confidence beat or a low confidence beat based on one or more characteristics of the individual pulses associated with the respective beats, wherein the classifying comprises, for each of the plurality of beats;

determining a pulse width for each of the individual pulses;

comparing the pulse width to a pulse width threshold;

incrementing a narrow pulse count for each of the pulses in which the pulse width satisfies the pulse width threshold;

determining that the narrow pulse count one of does not satisfy a narrow pulse count threshold or satisfies the narrow pulse count threshold;

for each of the plurality of beats for which the narrow pulse count does not satisfy the narrow pulse count threshold, classifying the respective beat as a high confidence beat; and

for each of the plurality of beats for which the narrow pulse count satisfies the narrow pulse count threshold, classifying the respective beat as a low confidence beat;

identifying the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable based on the classifications of the plurality of beats;

detecting the cardiac event based on at least on the identifications of the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable, wherein the cardiac event requires therapy;

and

delivering the therapy for the cardiac event in response to the detecting.

2. The method of claim 1, wherein classifying each of the plurality of beats as one of a high confidence beat or a low confidence beat based on one or more characteristics of the individual pulses associated with the respective beats further comprises:

determining a pulse amplitude for each of the individual pulses associated with the respective beats; and

comparing the pulse amplitude to a pulse amplitude threshold,

wherein incrementing the narrow pulse count further comprises incrementing the narrow pulse count for each of the pulses in which the pulse amplitude satisfies the pulse amplitude threshold.

3. The method of claim 2, wherein the narrow pulse count threshold is equal to 5.

4. The method of claim 1, wherein identifying the first segment and/or the second segment as one of shockable or not shockable based on the classifications of the plurality of beats comprises:

identifying the segment as shockable when a number of beats of the segment classified as both non-match beats and high confidence beats satisfies a non-match threshold; and

identifying the segment as not shockable when the number of beats of the segment classified as both non-match beats and high confidence beats does not satisfy the non-match threshold.

5. The method of claim 4, wherein the non-match threshold is equal to 75 percent of the number of beats within the segment.

6. The method of claim 1, wherein determining, for each of the plurality of beats, whether the respective beat matches a template beat comprises determining, for each of the plurality of beats, whether a morphology metric of the respective beat matches a morphology metric of the template beat within a predetermined percentage.

7. The method of claim 1, further comprising:

in addition to identifying each of the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable based on the classifications of the respective plurality of beats within the first and second segment, separately identifying each of the first segment and the second segment as one of shockable or not shockable based on a gross morphology analysis of the first segment and the second segment,

wherein detecting the cardiac event based on the identifications of the first segment and the second segment as shockable or not shockable based on classifications of the plurality of beats and the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

8. The method of claim 7, further comprising:

determining a number of the plurality of beats of the first segment being classified as being low confidence beats; and

comparing the number of the plurality of beats of the first segment classified as being low confidence beats to an upper low confidence threshold,

wherein detecting the cardiac event comprises ignoring the identification of the first segment as being shockable or not shockable based on the beat classifications and the identification of the first segment as being shockable or not shockable based on the gross morphology analysis when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the upper low confidence threshold.

9. The method of claim 8, further comprising:

comparing the number of the plurality of beats of the first segment being classified as being low confidence beats to a lower low confidence threshold, the lower low confidence threshold being less than the upper low confidence threshold,

wherein detecting the cardiac event comprises;

ignoring the identification of the first segment as being shockable or not shockable based on the beat classifications when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the lower low confidence threshold and does not satisfy the upper low confidence threshold; and

detecting the cardiac event based only on the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

10. The method of claim 7, further comprising:

comparing the number of the plurality of beats of the first segment being classified as being low confidence beats to a lower low confidence threshold, the lower low confidence threshold being less than the upper low confidence threshold,

wherein detecting the cardiac event comprises;

ignoring the identification of the first segment as being shockable or not shockable based on the beat classifications when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the lower low confidence threshold and does not satisfy the upper low confidence threshold; and

detecting the cardiac event based only on the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

11. The method of claim 1, wherein detecting the cardiac event comprises transitioning from a first detection state to a second detection state.

12. The method of claim 11, further comprising, while in the second detection state, charging high voltage capacitors.

13. The method of claim 1, further comprising delivering a cardioversion-defibrillation shock.

27. The method of claim 1, further comprising:

obtaining a third cardiac signal sensed via the first set of electrodes forming the first sensing vector;

obtaining a fourth cardiac signal sensed via the second set of electrodes forming the second sensing vector;

identifying a plurality of beats within a third segment of the third cardiac signal and a fourth segment of the fourth cardiac signal, the fourth segment being sensed simultaneously with the third segment;

analyzing each of the plurality of beats of the third segment and the fourth segment, wherein the analyzing includes;

determining, for each of the plurality of beats, whether the respective beat matches a template beat;

classifying beats of the plurality of beats that match the template beat as match beats and beats of the plurality of beats that do not match the template beat as non-match beats;

determining, for each of the plurality of beats, individual pulses associated with the respective beats; and

classifying each of the plurality of beats as one of a high confidence beat or a low confidence beat based on one or more characteristics of the individual pulses associated with the respective beats, wherein the classifying comprises, for each of the plurality of beats;

determining a pulse width for each of the individual pulses;

comparing the pulse width to a pulse width threshold;

incrementing a narrow pulse count for each of the pulses in which the pulse width satisfies the pulse width threshold;

determining that the narrow pulse count one of does not satisfy a narrow pulse count threshold or satisfies the narrow pulse count threshold;

for each of the plurality of beats for which the narrow pulse count does not satisfy the narrow pulse count threshold, classifying the respective beat as a high confidence beat; and

for each of the plurality of beats for which the narrow pulse count satisfies the narrow pulse count threshold, classifying the respective beat as a low confidence beat;

identifying the third segment of the third cardiac signal and the fourth segment of the fourth cardiac signal as one of shockable or not shockable based on the classifications of the plurality of beats;

not detecting the cardiac event based on at least on the identifications of the third segment of the third cardiac signal and the fourth segment of the fourth cardiac signal as one of shockable or not shockable, wherein the cardiac event requires therapy; and

not delivering the therapy for the cardiac event in response to the not detecting.

14. An medical device comprising:

circuitry configured to obtain a first cardiac signal sensed via a first set of electrodes electrically coupled to the circuitry and forming a first sensing vector and to obtain a second cardiac signal sensed via a second set of electrodes electrically coupled to the circuitry and forming a second sensing vector;

a processor configured to;

identify a plurality of beats within a first segment of the first cardiac signal and a second segment of the second cardiac signal, the second segment being sensed simultaneously with the first segment;

determine, for each of the plurality of beats, whether the respective beat matches a template beat;

classify beats of the plurality of beats that match the template beat as match beats and beats of the plurality of beats that do not match the template beat as non-match beats;

determine, for each of the plurality of beats, a plurality of pulses associated with the respective beats;

classify each of the plurality of beats as one of a high confidence beat or a low confidence beat based on one or more characteristics of the plurality of pulses associated with the respective beats by at least, for each of the plurality of beats;

determining a pulse width for each of the individual pulses;

comparing the pulse width to a pulse width threshold;

incrementing a narrow pulse count for each of the pulses in which the pulse width satisfies the pulse width threshold;

determining that the narrow pulse count one of does not satisfy a narrow pulse count threshold or satisfies the narrow pulse count threshold;

for each of the plurality of beats for which the narrow pulse count does not satisfy the narrow pulse count threshold, classifying the respective beat as a high confidence beat; and

for each of the plurality of beats for which the narrow pulse count satisfies the narrow pulse count threshold, classifying the respective beat as a low confidence beat;

identify the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable based on the classifications of the plurality of beats;

detecting a cardiac event based on at least on the identifications of the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable, wherein the cardiac event requires therapy; and

delivering the therapy for the cardiac event in response to the detecting.

15. The implantable medical device of claim 14, wherein the processor is configured to classify each of the plurality of beats as one of a high confidence beat or a low confidence beat by:

determining a pulse amplitude for each of the individual pulses associated with the respective beats; and

comparing the pulse amplitude to a pulse amplitude threshold,

wherein incrementing the narrow pulse count further comprises incrementing the narrow pulse count for each of the pulses in which the pulse amplitude satisfies the pulse amplitude threshold.

16. The medical device of claim 15, wherein the narrow pulse count threshold is equal to 5.

17. The medical device of claim 14, wherein the processor is configured to identify the first segment and/or the second segment as one of shockable or not shockable based on the classifications of the plurality of beats by:

identifying the segment as shockable when a number of beats of the segment classified as both non-match beats and high confidence beats satisfies a non-match threshold; and

identifying the segment as not shockable when the number of beats of the segment classified as both non-match beats and high confidence beats does not satisfy the non-match threshold.

18. The medical device of claim 17, wherein the non-match threshold is equal to 75 percent of the number of beats within the segment.

19. The medical device of claim 14, wherein the processor is configured to determine, for each of the plurality of beats, whether the respective beat matches a template beat by determining, for each of the plurality of beats, whether a morphology metric of the respective beat matches a morphology metric of the template beat within a predetermined percentage.

20. The medical device of claim 14, wherein the processor is further configured to:

in addition to identifying each of the first segment of the first cardiac signal and the second segment of the second cardiac signal as one of shockable or not shockable based on the classifications of the respective plurality of beats within the first and second segment, separately identify each of the first segment and the second segment as one of shockable or not shockable based on a gross morphology analysis of the first segment and the second segment,

wherein the processor is configured to detect the cardiac event based on the identifications of the first segment and the second segment as shockable or not shockable based on classifications of the plurality of beats and the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

21. The medical device of claim 20, wherein the processor is further configured to:

determine a number of the plurality of beats of the first segment being classified as being low confidence beats;

compare the number of the plurality of beats of the first segment classified as being low confidence beats to an upper low confidence threshold; and

ignore the identification of the first segment as being shockable or not shockable based on the beat classifications and the identification of the first segment as being shockable or not shockable based on the gross morphology analysis when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the upper low confidence threshold.

22. The medical device of claim 21, wherein the processor is further configured to:

compare the number of the plurality of beats of the first segment being classified as being low confidence beats to a lower low confidence threshold, the lower low confidence threshold being less than the upper low confidence threshold;

ignore the identification of the first segment as being shockable or not shockable based on the beat classifications when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the lower low confidence threshold and does not satisfy the upper low confidence threshold; and

detect the cardiac event based only on the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

23. The medical device of claim 20, wherein the processor is further configured to:

compare the number of the plurality of beats of the first segment being classified as being low confidence beats to a lower low confidence threshold, the lower low confidence threshold being less than the upper low confidence threshold;

ignore the identification of the first segment as being shockable or not shockable based on the beat classifications when the number of the plurality of beats of the first segment classified as being low confidence beats satisfies the lower low confidence threshold and does not satisfy the upper low confidence threshold; and

detect the cardiac event based only on the identifications of the first segment and the second segment as shockable or not shockable based on the gross morphology analysis.

24. The medical device of claim 14, wherein the processor is configured to detect the cardiac event by at least transitioning from a first detection state to a second detection state.

25. The medical device of claim 24, further comprising:

one or more capacitors; and

a charging circuit electrically coupled to the one or more capacitors,

wherein the processor is further configured to initiate the charging of the one or more capacitors by the charging circuit while in the second detection state.

26. The medical device of claim 14, further comprising:

one or more capacitors; and

a high voltage output circuit electrically coupled to the one or more capacitors,

wherein the high voltage output circuit delivers a cardioversion-defibrillation shock based on the processors determination of whether to deliver therapy for the cardiac event.

28. The medical device of claim 14, wherein the circuitry is further configured to obtain a third cardiac signal sensed via the first set of electrodes and to obtain a fourth cardiac signal sensed via the second set of electrodes, and wherein the processor is further configured to:

obtain a third cardiac signal sensed via the first set of electrodes forming the first sensing vector;

obtain a fourth cardiac signal sensed via the second set of electrodes forming the second sensing vector;

identifying a plurality of beats within a third segment of the third cardiac signal and a fourth segment of the fourth cardiac signal, the fourth segment being sensed simultaneously with the third segment;

analyze each of the plurality of beats of the third segment and the fourth segment, wherein the analyzing includes;

determine, for each of the plurality of beats, whether the respective beat matches a template beat;

classify beats of the plurality of beats that match the template beat as match beats and beats of the plurality of beats that do not match the template beat as non-match beats;

determine, for each of the plurality of beats, individual pulses associated with the respective beats; and

classify each of the plurality of beats as one of a high confidence beat or a low confidence beat based on one or more characteristics of the individual pulses associated with the respective beats, wherein the processor is configured to classify each of the plurality of beats by at least;

determining a pulse width for each of the individual pulses;

comparing the pulse width to a pulse width threshold;

incrementing a narrow pulse count for each of the pulses in which the pulse width satisfies the pulse width threshold;

determining that the narrow pulse count one of does not satisfy a narrow pulse count threshold or satisfies the narrow pulse count threshold;

for each of the plurality of beats for which the narrow pulse count does not satisfy the narrow pulse count threshold, classifying the respective beat as a high confidence beat; and

for each of the plurality of beats for which the narrow pulse count satisfies the narrow pulse count threshold, classifying the respective beat as a low confidence beat;

identify the third segment of the third cardiac signal and the fourth segment of the fourth cardiac signal as one of shockable or not shockable based on the classifications of the plurality of beats;

not detect the cardiac event based on at least on the identifications of the third segment of the third cardiac signal and the fourth segment of the fourth cardiac signal as one of shockable or not shockable, wherein the cardiac event requires therapy; and

not deliver the therapy for the cardiac event in response to the not detecting.