METHOD AND APPARATUS FOR DISCRIMINATING TACHYCARDIA EVENTS IN A MEDICAL DEVICE

• US 20150273229A1
• Filed: 04/01/2014
• Published: 10/01/2015
• Est. Priority Date: 04/01/2014
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng, Stadler, Robert W.
• Granted Patent: US 9,526,908 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

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 and a second sensing vector, determining, in response to the cardiac event being identified as a shockable event, a first R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the first sensing vector during the predetermined sensing window and a second R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the second sensing vector, determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector satisfy a morphology metric, and identifying the cardiac event as one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia in response to the determined first R-wave morphology, second R-wave morphology, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not satisfying the morphology metric.

Claims

1. A method of discriminating a cardiac event as being one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia in a medical device, comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

identifying the cardiac event as one of a shockable event and a non-shockable event in response to a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector;

determining, in response to the cardiac event being identified as a shockable event, a first R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the first sensing vector during the predetermined sensing window and a second R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the second sensing vector;

determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector satisfy a morphology metric; and

identifying the cardiac event as one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia in response to the determined first R-wave morphology, second R-wave morphology, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not satisfying the morphology metric.

2. The method of claim 1, further comprising:

comparing the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template;

determining whether a beat morphology match is satisfied in response to the comparing; and

identifying the cardiac event as polymorphic ventricular tachycardia in response to the beat morphology match not being satisfied.

3. The method of claim 2, further comprising:

determining R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template;

determining whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths; and

identifying the cardiac event as a non-shockable event in response to both the beat morphology match being satisfied and the R-wave width threshold being satisfied for both the first sensing vector and the second sensing vector.

4. The method of claim 2, further comprising:

determining R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template;

determining whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths;

determining whether the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector satisfy a signal metric; and

identifying the cardiac event as a non-shockable event in response to the beat morphology match being satisfied, the R-wave width threshold not being satisfied for both the first sensing vector and the second sensing vector, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector satisfying the signal metric.

5. The method of claim 2, further comprising:

determining R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template;

determining whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths; and

identifying the cardiac event as monomorphic ventricular tachycardia in response to the beat morphology match being satisfied, the R-wave width threshold not being satisfied for both the first sensing vector and the second sensing vector, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not satisfying the signal metric.

6. The method of claim 1, wherein determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector satisfy a signal metric comprises:

determining a first low slope content of the next interval subsequently sensed along the first sensing vector and a second low slope content of the next interval subsequently sensed along the second sensing vector;

determining a first normalized mean rectified amplitude of the next interval subsequently sensed along the first sensing vector and a second normalized mean rectified amplitude of the next interval subsequently sensed along the second sensing vector; and

determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector satisfy the signal metric in response to the determined first low slope content, second low slope content, first normalized mean rectified amplitude, and second normalized mean rectified amplitude.

7. The method of claim 1, further comprising delaying the determination of the identifying the cardiac as a shockable event in response the cardiac event being identified as monomorphic ventricular tachycardia.

8. The method of claim 5, further comprising:

delaying the determination of the identifying the cardiac as a shockable event in response the cardiac event being identified as monomorphic ventricular tachycardia;

comparing, during delay of identifying the cardiac event being shockable,

a first selected R-wave of the R-waves associated with the next interval subsequently sensed along the first sensing vector with R-waves associated with the next interval subsequently sensed along the first sensing vector other than the first selected R-wave;

comparing a second selected R-wave of the R-waves associated with the next interval subsequently sensed along the second sensing vector with R-waves associated with the next interval subsequently sensed along the second sensing vector other than the second selected R-wave; and

determining whether the third interval and the fourth interval correspond to monomorphic ventricular tachycardia in response to the comparing.

9. The method of claim 8, further comprising confirming the cardiac event being identified as a shockable event in response to both the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector being determined to correspond to monomorphic ventricular tachycardia.

10. The method of claim 9, further comprising:

determining, in response to one or both of the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not being determined to correspond to monomorphic ventricular tachycardia, whether the cardiac event has terminated; and

determining whether to deliver therapy in response to the determining whether the cardiac event has terminated.

11. A medical device for delivering therapy in response to a cardiac event, comprising:

a plurality of electrodes to sense cardiac signal, the plurality of electrodes forming a first sensing vector and a second sensing vector;

a housing having circuitry positioned therein electrically couple to the plurality of electrodes; and

a processor positioned within the housing and configured to identify the cardiac event as one of a shockable event and a non-shockable event in response to a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector, determine, in response to the cardiac event being identified as a shockable event, a first R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the first sensing vector during the predetermined sensing window and a second R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the second sensing vector, determine whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector are within a ventricular tachycardia shock zone, and identify the cardiac event as one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia in response to the determined first R-wave morphology, second R-wave morphology, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector being within the ventricular tachycardia shock zone.

12. The medical device of claim 11, wherein the processor is further configured to compare the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template, determine whether a ventricular tachycardia morphology match is satisfied in response to the comparing, and identify the cardiac event as polymorphic ventricular tachycardia in response to the ventricular tachycardia morphology match not being satisfied.

13. The medical device of claim 12, wherein the processor is further configured to determine R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template, determine whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths, and identify the cardiac event as a non-shockable event in response to both the ventricular tachycardia morphology match being satisfied and the R-wave width threshold being satisfied for both the first sensing vector and the second sensing vector.

14. The medical device of claim 12, wherein the processor is further configured to determine R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template, determine whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths, and identify the cardiac event as a non-shockable event in response to the ventricular tachycardia morphology match being satisfied, the R-wave width threshold not being satisfied for both the first sensing vector and the second sensing vector, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not being within the ventricular tachycardia shock zone.

15. The medical device of claim 12, wherein the processor is further configured to determine R-wave widths of the R-waves of the next interval subsequently sensed along the first sensing vector and the R-waves of the next interval subsequently sensed along the second sensing vector to an R-wave template, determine whether an R-wave width threshold is satisfied for both the first sensing vector and the second sensing vector in response to the determined R-wave widths, and identify the cardiac event as monomorphic ventricular tachycardia in response to the ventricular tachycardia morphology match being satisfied, the R-wave width threshold not being satisfied for both the first sensing vector and the second sensing vector, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector being within the ventricular tachycardia shock zone.

16. The medical device of claim 11, wherein determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector are within a ventricular tachycardia shock zone comprises:

determining a first low slope content of the next interval subsequently sensed along the first sensing vector and a second low slope content of the next interval subsequently sensed along the second sensing vector;

determining a first normalized mean rectified amplitude of the next interval subsequently sensed along the first sensing vector and a second normalized mean rectified amplitude of the next interval subsequently sensed along the second sensing vector; and

determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector are within a ventricular tachycardia shock zone in response to the determined first low slope content, second low slope content, first normalized mean rectified amplitude, and second normalized mean rectified amplitude.

17. The medical device of claim 11, wherein the processor is further configured to delay the determination of the identifying the cardiac as a shockable event in response the cardiac event being identified as monomorphic ventricular tachycardia.

18. The medical device of claim 15, wherein the processor is further configured to delay the determination of the identifying the cardiac as a shockable event in response the cardiac event being identified as monomorphic ventricular tachycardia, compare, during delay of identifying the cardiac event being shockable, a first selected R-wave of the R-waves associated with the next interval subsequently sensed along the first sensing vector with R-waves associated with the next interval subsequently sensed along the first sensing vector other than the first selected R-wave, compare a second selected R-wave of the R-waves associated with the next interval subsequently sensed along the second sensing vector with R-waves associated with the next interval subsequently sensed along the second sensing vector other than the second selected R-wave, and determine whether the third interval and the fourth interval correspond to monomorphic ventricular tachycardia in response to the comparing.

19. The medical device of claim 18, wherein the processor is further configured to confirm the cardiac event being identified as a shockable event in response to both the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector being determined to correspond to monomorphic ventricular tachycardia.

20. The medical device of claim 19, wherein the processor is further configured to determine, in response to one or both of the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector not being determined to correspond to monomorphic ventricular tachycardia, whether the cardiac event has terminated, and determine whether to deliver therapy in response to the determining whether the cardiac event has terminated.

21. A non-transitory, computer-readable storage medium storing instructions for causing a processor included in a medical device to perform a method for discriminating a cardiac event as being one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia, the method comprising:

sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;

identifying the cardiac event as one of a shockable event and a non-shockable event in response to a first interval sensed along the first sensing vector during a predetermined sensing window and a second interval simultaneously sensed along the second sensing vector;

determining, in response to the cardiac event being identified as a shockable event, a first R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the first sensing vector during the predetermined sensing window and a second R-wave morphology corresponding to R-waves of a next interval subsequently sensed along the second sensing vector;

determining whether the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector are within a ventricular tachycardia shock zone; and

identifying the cardiac event as one of a monomorphic ventricular tachycardia and a polymorphic ventricular tachycardia in response to the determined first R-wave morphology, second R-wave morphology, and the next interval subsequently sensed along the first sensing vector and the next interval subsequently sensed along the second sensing vector being within the ventricular tachycardia shock zone.