Atrial arrhythmia episode detection in a cardiac medical device

Patent metadata

Field	Value
Publication number	US-9675261-B2
Application number	US-201615004202-A
Country	US
Kind code	B2
Filing date	Jan 22, 2016
Priority date	Jan 23, 2015
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

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.

First claim

The invention claimed is:

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 bas

Assignees

• Medtronic Inc

Inventors

• Cao Jian
• Degroot Paul J

Classifications

• G16H50/20

  for computer-aided diagnosis, e.g. based on medical expert systems · CPC title

• A61N1/3987

  characterised by the timing or triggering of the shock · CPC title

• A61N1/3956

  Implantable devices for applying electric shocks to the heart, e.g. for cardioversion · CPC title

• A61N1/3702

  Physiological parameters (A61N1/365 takes precedence; evoked response A61N1/371) · CPC title

• A61N1/3624

  occurring in the atrium, i.e. atrial tachycardia · CPC title