Atrial arrhythmia episode detection in a cardiac medical device

• US 9,675,261 B2
• Filed: 01/22/2016
• Issued: 06/13/2017
• Est. Priority Date: 01/23/2015
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Cao, Jian, Degroot, Paul J.
• Primary Examiner(s): Wieland, Robert N
• Application Number:
  US15/004,202
• Publication Number:
  US 20160213270A1
• Time in Patent Office: 508 Days
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/353 Detecting P-waves
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• 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: 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 1/3624 occurring in the atrium, i.e. atrial tachycardia
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• 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 a cardiac signal, identifying R-waves in the cardiac signal attendant ventricular depolarizations, determining RR-intervals between successive R-waves in response to the sensed cardiac signal, detecting an atrial tachyarrhythmia based on an analysis of the RR-intervals, iteratively sensing groups of a predetermined number of P-waves attendant atrial depolarizations in response to detecting the atrial tachyarrhythmia, and confirming the atrial tachyarrhythmia based on an analysis of the iteratively sensed groups of P-waves.

Claims

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

sensing a cardiac signal;

identifying R-waves in the cardiac signal attendant ventricular depolarizations;

determining RR-intervals between successive R-waves in the sensed cardiac signal;

detecting an atrial tachyarrhythmia based on an analysis of the RR-intervals;

iteratively sensing groups of a predetermined number of P-waves attendant atrial depolarizations in response to detecting the atrial tachyarrhythmia; and

confirming the atrial tachyarrhythmia based on an analysis of the iteratively sensed groups of P-waves.

2. The method of claim 1, wherein confirming the atrial tachyarrhythmia based on the analysis of the iteratively sensed groups of P-waves comprises:

determining P-wave parameters associated with each P-wave of the predetermined number of P-waves;

determining relative differences between the P-wave parameters;

determining whether each of the P-waves of the predetermined number of P-waves of an iteratively sensed group match each other based on the determined relative differences;

determining whether the predetermined number of P-waves of the iteratively sensed group match a P-wave template; and

updating a counter in response to the iteratively sensed group of P-waves matching each other and matching the P-wave template, wherein the atrial tachyarrhythmia is confirmed in response to the counter remaining less than a counter threshold at expiration of a predetermined time period.

3. The method of claim 2, wherein determining relative differences between the P-wave parameters, comprises:

determining a relative width difference for each of the P-waves; and

determining a relative amplitude difference for each of the P-waves.

4. The method of claim 2, further comprising:

determining the P-wave template prior to detecting the atrial tachyarrhythmia by sensing a second predetermined number of P-waves when a predetermined number of RR-intervals are greater than an interval threshold;

determining a baseline slope of each of the second predetermined number of P-waves;

adjusting each one of the second predetermined number of P-waves using the respective determined baseline slope, the adjusted P-wave having a zero baseline slope;

modifying each one of the adjusted P-waves by setting all points of the adjusted P-waves having an opposite polarity of a peak amplitude of the adjusted P-wave to zero;

determining a center of area of each of the modified P-waves;

aligning the centers of area of each of the modified P-waves; and

generating a P-wave template from the aligned, modified P-waves.

5. The method of claim 1, wherein iteratively sensing the groups of the predetermined number of P-waves comprises:

determining P-wave windows based on the determined RR-intervals; and

adjusting P-waves within the P-wave windows by determining a modified P-wave baseline.

6. The method of claim 2, further comprising:

determining a maximum amplitude of each of the P-waves;

determining, for each of the P-waves, a first minimum point and a second minimum point as a portion of the maximum amplitude;

determining an area of each of the P-waves based on a baseline extending between the first minimum baseline point and the second minimum baseline point;

determining a center of area window of each of the P-waves based on the area and a time interval extending between the first minimum point and the second minimum point; and

determining the P-wave parameters from the center of area windows determined for each of the respective P-waves.

7. The method of claim 6, wherein determining the center of area window of each of the P-waves comprises:

determining an amplitude of the center of area window from the area and the time interval between the first minimum point and the second minimum point of the respective P-wave; and

determining a width of the center of area window based on the time interval from the first minimum point and the second minimum point.

8. The method of claim 7, wherein determining the P-wave parameters, comprises:

determining a relative width difference based on the widths of the center of area windows determined for the P-waves; and

determining a relative amplitude difference based on the amplitudes of the center of area windows determined for the P-waves.

9. The method of claim 1, wherein the atrial tachyarrhythmia is atrial fibrillation.

10. The method of claim 9, further comprising at least one of withholding a ventricular therapy and storing an episode of the cardiac signal in response to confirming the atrial tachyarrhythmia.

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

sensing circuitry configured to receive a cardiac signal from a plurality of electrodes coupled to the medical device; and

a processor configured to;

identify R-waves in the cardiac signal attendant ventricular depolarizations;

determine RR-intervals between successive R-waves in the sensed cardiac signal,

detect an atrial tachyarrhythmia based on an analysis of the RR-intervals;

iteratively sense groups of a predetermined number of P-waves attendant atrial depolarizations in response to detecting the atrial tachyarrhythmia; and

confirm the atrial tachyarrhythmia based on an analysis of the iteratively sensed groups of P-waves.

12. The medical device of claim 11, wherein the processor is configured to confirm the atrial tachyarrhythmia based on the analysis of the iteratively sensed groups of P-waves by:

determining P-wave parameters associated with each P-wave of the predetermined number of P-waves;

determining relative differences between the P-wave parameters;

determining whether each of the P-waves of the predetermined number of P-waves of an iteratively sensed group match each other based on the determined relative differences;

determining whether the predetermined number of P-waves of the iteratively sensed group match a P-wave template; and

updating a counter in response to the iteratively sensed group of P-waves matching each other and matching the P-wave template, wherein the atrial tachyarrhythmia is confirmed in response to the counter remaining less than a counter threshold at expiration of a predetermined time period.

13. The medical device of claim 12, wherein the processor is configured to determine relative differences between the P-wave parameters by:

determining a relative width difference for each of the P-waves; and

determining a relative amplitude difference for each of the P-waves.

14. The medical device of claim 12, wherein the processor is further configured to:

determine the P-wave template prior to detecting the atrial tachyarrhythmia by sensing a second predetermined number of P-waves when a predetermined number of RR-intervals are greater than an interval threshold;

determine a baseline slope of each of the second predetermined number of P-waves;

adjust each one of the second predetermined number of P-waves using the respective determined baseline slope, the adjusted P-wave having a zero baseline slope;

modify each one of the adjusted P-waves by setting all points of the adjusted P-waves having an opposite polarity of a peak amplitude of the adjusted P-wave to zero;

determine a center of area of each of the modified P-waves;

align the centers of area of each of the modified P-waves; and

generate a P-wave template from the aligned, modified P-waves.

15. The medical device of claim 11, wherein the processor is configured to iteratively sense the groups of the predetermined number of P-waves by:

determining P-wave windows based on the determined RR-intervals; and

adjusting P-waves within the P-wave windows by determining a modified P-wave baseline.

16. The medical device of claim 12, wherein the processor is further configured to:

determine a maximum amplitude of each of the P-waves;

determine, for each of the P-waves, a first minimum point and a second minimum point as a portion of the maximum amplitude;

determine an area of each of the P-waves based on a baseline extending between the first minimum baseline point and the second minimum baseline point;

determine a center of area window of each of the P-waves based on the area and a time interval extending between the first minimum point and the second minimum point; and

determine the P-wave parameters from the center of area windows determined for each of the respective P-waves.

17. The medical device of claim 16, wherein the processor is configured to determine the center of area window of each of the P-waves by:

determining an amplitude of the center of area window from the area and the time interval between the first minimum point and the second minimum point of the respective P-wave; and

determining a width of the center of area window based on the time interval from the first minimum point and the second minimum point.

18. The medical device of claim 17, wherein the processor is further configured to determine the P-wave parameters, by:

determining a relative width difference based on the widths of the center of area windows determined for the P-waves; and

determining a relative amplitude difference based on the amplitudes of the center of area windows determined for the P-waves.

19. The medical device of claim 11, wherein the processor is configured to detect the atrial tachyarrhythmia as atrial fibrillation.

20. The medical device of claim 19, further comprising therapy output circuitry and a memory, wherein the processor is further configured to provide a response to confirming the atrial tachyarrhythmia, the response comprising at least one of controlling the therapy output circuitry to withhold a ventricular therapy and storing an episode of the cardiac signal in the memory.

21. The medical device of claim 11, wherein the plurality of electrodes are carried by an extra-cardiovascular lead.

23. The medical device of claim 11, wherein the processor is configured to iteratively sense the groups of the predetermined number of P-waves by:

setting a timer; and

iteratively sensing the groups of the predetermined number of P-waves until the timer expires.

22. A non-transitory, computer-readable storage medium storing instructions for causing a processor included in a medical device to perform a method for detecting a cardiac event, the method comprising:

sensing a cardiac signal;

identifying R-waves in the cardiac signal attendant ventricular depolarizations;

determining RR-intervals between successive R-waves in response to the sensed cardiac signal;

detecting an atrial tachyarrhythmia based on an analysis of the RR-intervals;

iteratively sensing groups of a predetermined number of P-waves attendant atrial depolarizations in response to detecting the atrial tachyarrhythmia; and

confirming the atrial tachyarrhythmia based on an analysis of the iteratively sensed groups of P-waves.