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

• US 10,065,045 B2
• Filed: 04/03/2017
• Issued: 09/04/2018
• Est. Priority Date: 07/01/2014
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng
• Primary Examiner(s): Layno, Carl H
• Assistant Examiner(s): Morales, Jon Eric C
• Application Number:
  US15/477,475
• Publication Number:
  US 20170203114A1
• Time in Patent Office: 519 Days
• Field of Search: 600515, 607 14
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/346 Analysis of electrocardiograms
• CPC Class Codes: A61B 5/35 by template matching
• 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 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock
• CPC Class Codes: G16H 50/20 : for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A method and medical device for detecting a cardiac event that includes sensing cardiac signals from a plurality of electrodes, sensing a plurality of beats in response to the sensed cardiac signals, identifying each beat of the plurality of beats as one of a normal beat and a not normal beat, determining at least one of whether a number of beats identified as a normal beat is greater than a normal beat threshold, whether an RR interval associated with the beats identified as being a normal beat is less than a threshold interval, and whether RR intervals associated with the beats identified as being normal beats are within an RR interval range, and identifying the cardiac event as being one of shockable and not shockable in response to the determining.

Claims

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

sensing a cardiac signal on a first sensing vector formed from a plurality of electrodes;

determining a sensing window that includes a plurality of beats within a portion of the sensed cardiac signal;

identifying each beat of the plurality of beats within the sensing window as one of a normal beat and a not normal beat;

determining whether periodic normal beats occur in the sensing window; and

identifying the cardiac event as being not shockable based at least on the determination that periodic normal beats occur in the sensing window;

identifying the cardiac event as being shockable based at least on the determination that periodic normal beats do not occur in the sensing window; and

delivering a shock to treat the cardiac event identified as being shockable.

2. The method of claim 1, further comprising:

performing a gross morphology analysis of the whole cardiac signal sensed on the first sensing vector during the sensing window; and

identifying the cardiac event as being shockable based on both the performed gross morphology analysis identifying the cardiac event as shockable and the determination that periodic normal beats do not occur in the sensing window.

3. The method of claim 1, wherein the sensing window comprises a first sensing window, the method further comprising:

determining a second, consecutive sensing window that includes a second plurality of beats within a second portion of the sensed cardiac signal, the second, consecutive sensing window occurring subsequent to the first sensing window;

determining a distribution of the normal beats occurring within the first sensing window and the second sensing window;

comparing the distribution of the normal beats to a normal beats distribution threshold;

identifying the cardiac event as being not shockable based at least on the determined distribution being greater than or equal to the normal beats distribution threshold; and

identifying the cardiac event as being shockable based at least on the determined distribution is less than the normal beats distribution threshold.

4. The method of claim 3 , further comprising:

comparing a number of beats identified as being normal beats within the first and second sensing windows to a predetermined threshold;

identifying the cardiac event as being not shockable based at least on the determination that number of beats identified as being normal beats within the first and second sensing windows is less than or equal to the predetermined threshold; and

identifying the cardiac event as being shockable based at least on the determination that number of beats identified as being normal beats within the first and second sensing windows is greater than to the predetermined threshold.

5. The method of claim 4, wherein the predetermined threshold comprises a proportion of the plurality of beats.

6. The method of claim 1, wherein the sensing window comprises a first sensing window, the method further comprising:

determining a second, consecutive sensing window that includes a second plurality of beats within a second portion of the sensed cardiac signal, the second, consecutive sensing window occurring subsequent to the first sensing window;

determining whether one or more normal beats occur within the second sensing window;

identifying the cardiac event as being not shockable based at least on the determination that one or more normal beats occur within the second sensing window; and

identifying the cardiac event as being shockable based at least on the determination that one or more normal beats do not occur within the second sensing window.

7. The method of claim 1, wherein determining whether periodic normal beats occur in the sensing window comprises:

determining that a number of beats identified as normal beats is greater than or equal to a normal beat threshold;

identifying RR intervals between consecutive ones of the normal beats;

determining that at least one of the RR intervals is greater than or equal to an interval threshold;

determining that the RR intervals are within an RR interval range; and

determining that periodic normal beats occur in the sensing window when it is determined that the RR intervals are within the RR interval range.

8. The method of claim 7, wherein determining that the RR intervals are within the RR interval range comprises:

comparing a length of a first RR interval of the RR intervals to lengths of RR intervals of the RR intervals other than the first RR interval;

determining that the length of the first RR interval is within a predetermined fraction of the lengths of the RR intervals other than the first RR interval; and

determining the RR intervals are within the RR interval range when the length of the first RR interval is determined to be within the predetermined fraction of the lengths of the RR intervals other than the first RR interval.

9. The method of claim 8, wherein the predetermined fraction is one sixteenth of the length of the first RR interval.

10. The method of claim 1, further comprising:

sensing a second cardiac signal on a second sensing vector formed from the plurality of electrodes;

determining a second sensing window that includes a plurality of beats within a portion of the second sensed cardiac signal;

identifying each beat of the plurality of beats within the second sensing window as one of a normal beat and a not normal beat;

determining whether periodic normal beats occur in the second sensing window; and

identifying the cardiac event as being not shockable based at least on the determination that periodic normal beats occur in at least one of the first sensing window or the second sensing window; and

identifying the cardiac event as being shockable based at least on the determination that periodic normal beats do not occur in either of the first and second sensing windows.

11. The method of claim 1, further comprising:

sensing a second cardiac signal on a second sensing vector formed from the plurality of electrodes;

determining a second sensing window that includes a plurality of beats within a portion of the second sensed cardiac signal;

identifying each beat of the plurality of beats within the second sensing window as one of a normal beat and a not normal beat;

determining whether periodic normal beats occur in the second sensing window; and

performing a gross morphology analysis of the whole cardiac signal sensed on the second sensing vector during the second sensing window; and

identifying the cardiac event as being shockable based on the performed gross morphology analysis identifying the cardiac event as shockable in both the first and second sensing window and the determination that periodic normal beats do not occur in either the first and second sensing windows.

12. A medical device for detecting a cardiac event, comprising:

a sense amplifier configured to obtain a cardiac signal sensed on a first sensing vector formed from a plurality of electrodes coupled to the sense amplifier; and

a processor configured to determine a sensing window that includes a portion of the sensed cardiac signal having a plurality of beats, identify each beat of the plurality of beats within the sensing window as one of a normal beat and a not normal beat, determine whether periodic normal beats occur in the sensing window, identifying the cardiac event as being not shockable based at least on the determination that periodic normal beats occur in the sensing window, identify the cardiac event as being shockable based at least on the determination that periodic normal beats do not occur in the sensing window, and deliver a shock to treat the cardiac event identified as being shockable.

13. The medical device of claim 12, the processor further configured to perform a gross morphology analysis of the whole cardiac sensed on the first sensing vector during the sensing window, and identify the cardiac event as being shockable based on both the performed gross morphology analysis identifying the cardiac event as shockable and the determination that periodic normal beats do not occur in the sensing window.

14. The medical device of claim 12, wherein the sensing window comprises a first sensing window and the processor is further configured to determine a second, consecutive sensing window that includes a second plurality of beats within a second portion of the sensed cardiac signal, the second, consecutive sensing window occurring subsequent to the first sensing window, determine a distribution of the normal beats occurring within the first sensing window and the second sensing window, compare the distribution of the normal beats to a normal beats distribution threshold;

identify the cardiac event as being not shockable based at least on the determined distribution being greater than or equal to the normal beats distribution threshold; and

identify the cardiac event as being shockable based at least on the determined distribution is less than the normal beats distribution threshold.

15. The medical device of claim 12, wherein the sensing window comprises a first sensing window, the processor further configured to determine a second, consecutive sensing window that includes a second plurality of beats within a second portion of the sensed cardiac signal, the second, consecutive sensing window occurring subsequent to the first sensing window, determine whether one or more normal beats occur within the second sensing window, identify the cardiac event as being not shockable based at least on the determination that one or more normal beats occur within the second sensing window, and identify the cardiac event as being shockable based at least on the determination that one or more normal beats do not occur within the second sensing.

16. The medical device of claim 14, wherein the processor is further configured to compare a number of beats identified as being normal beats within the first and second sensing windows to a predetermined threshold, identify the cardiac event as being not shockable based at least on the determination that number of beats identified as being normal beats within the first and second sensing windows is less than or equal to the predetermined threshold, and identify the cardiac event as being shockable based at least on the determination that number of beats identified as being normal beats within the first and second sensing windows is greater than to the predetermined threshold.

17. The medical device of claim 16, wherein the predetermined threshold comprises a proportion of the plurality of beats.

18. The medical device of claim 12, wherein the processor is configured to determine whether periodic normal beats occur in the sensing window by:

determining that a number of beats identified as normal beats is greater than or equal to a normal beat threshold;

identifying RR intervals between consecutive ones of the normal beats;

determining that at least one of the RR intervals is greater than or equal to an interval threshold;

determining that the RR intervals are within an RR interval range; and

determining that periodic normal beats occur in the sensing window when it is determined that the RR intervals are within the RR interval range.

19. The medical device of claim 18, wherein the processor is configured to determine that the RR intervals are within the RR interval range by:

comparing a length of a first RR interval of the RR intervals to lengths of RR intervals of the RR intervals other than the first RR interval;

determining that the length of the first RR interval is within a predetermined fraction of the lengths of the RR intervals other than the first RR interval; and

determining the RR intervals are within the RR interval range when the length of the first RR interval is determined to be within the predetermined fraction of the lengths of the RR intervals other than the first RR interval.

20. The medical device of claim 19, wherein the predetermined fraction is one sixteenth of the length of the first RR interval.