Method and apparatus for atrial arrhythmia episode detection

Patent metadata

Field	Value
Publication number	US-9486155-B2
Application number	US-201514695135-A
Country	US
Kind code	B2
Filing date	Apr 24, 2015
Priority date	Feb 18, 2015
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

A method and medical device for determining a P-wave of a cardiac signal that includes sensing the cardiac signal, determining a P-wave sensing window in response to the sensed cardiac signal, the P-wave sensing window having a first portion and a second portion, determining signal characteristics of the sensed cardiac signal within the first portion and within the second portion, comparing the determined signal characteristics, and determining the P-wave in response to the comparing.

First claim

The invention claimed is:

1. A method of determining a P-wave of a cardiac signal in an implantable medical device, comprising:
sensing the cardiac signal;
identifying one or more R-waves within the cardiac signal;
determining one or more P-wave sensing windows, wherein each of the P-wave sensing window is associated with one of the one or more identified R-waves;
determining a characteristic P-wave sensing window based on the one or more determined P-wave sensing windows, the characteristic P-wave sensing window having a first portion and a second portion;
determining a first derivative signal of the cardiac signal within the characteristic P-wave sensing window;
determining a second derivative signal of the cardiac signal within the characteristic P-wave sensing window;
analyzing the first derivative and the second derivative of the cardiac signal within the characteristic P-wave window to determine a first set of signal characteristics of the cardiac signal within the first portion of the characteristic P-wave sensing window and a second set of signal characteristics of the cardiac signal within the second portion of the characteristic P-wave sensing window, the signal characteristics including zero crossings of the first derivative signal and amplitudes of the second derivative signal corresponding to the determined zero crossings; and
detecting the P-wave based on the first and the second set of signal characteristics.

2. The method of claim 1 , further comprising:
determining a maximum amplitude of the determined amplitudes of the second derivative signal within the first portion; and
comparing the amplitudes of the second derivative signal within the second portion to an amplitude threshold, wherein the amplitude threshold is determined based on the determined maximum amplitude of the second derivative signal within the first portion.

3. The method of claim 2 , wherein the amplitude threshold comprises a multiple of the determined maximum amplitude of the second derivative signal within the first portion.

4. The method of claim 2 , further comprising:
determining a number of times the determined amplitudes of the second derivative signal within the second portion are greater than the amplitude threshold; and
determining the P-wave based on the determined number of times.

5. The method of claim 4 , further comprising:
determining an RR-interval associated with one of the one or more determined R-wave;
determining a relative change associated with the RR-interval;
comparing the determined RR-interval to an interval threshold and the determined relative change to a change threshold; and
confirming the determined R-wave, wherein the P-wave sensing window is determined in response to the confirmed R-wave.

6. The method of claim 1 , further comprising:
determining a maximum amplitude of the determined amplitudes of the second derivative signal within the first portion;
determining a maximum amplitude threshold based on the determined maximum amplitude of the second derivative signal within the first portion;
determining a minimum amplitude of the determined amplitudes of the second derivative signal within the first portion;
determining a minimum amplitude threshold based on the determined minimum amplitude of the second derivative signal within the first portion; and
comparing the amplitudes of the second derivative signal within the second portion to the maximum amplitude threshold and the minimum amplitude threshold.

7. The method of claim 6 , further comprising:
determining a first number of times the determined amplitudes of the second derivative signal within the second portion are greater than the maximum amplitude threshold;
determining a second number of times the determined amplitudes of the second derivative signal within the second portion are less than the minimum amplitude threshold; and
determining the P-wave based on both the determined first number of times and the determined second number of times.

8. The method of claim 7 , further comprising determining the sensed cardiac signal within the first portion and within the second portion as a P-wave in response to either the first number of times being equal to one or the second number of times being equal to one.

9. The method of claim 1 , wherein the medical device comprises a subcutaneous device.

10. An implantable medical device for determining a P-wave in a cardiac signal, comprising:
a plurality of electrodes configured to sense the cardiac signal; and
a processor configured to identify one or more R-waves within the cardiac signal, determine one or more P-wave sensing windows, wherein each of the P-wave sensing windows is associated with one of the one or more identified R-waves, determine a characteristic P-wave sensing window based on the one or more determined P-wave sensing windows, the characteristic P-wave sensing window having a first portion and a second portion, determine a first derivative signal of the cardiac signal within the characteristic P-wave sensing window, determine a second derivative signal of the cardiac signal within the characteristic P-wave sensing window, analyze the first derivative and the second derivative of the cardiac signal within the characteristic P-wave window to determine a first set of signal characteristics of the cardiac signal within the first portion of the characteristic P-wave sensing window and a second set of signal characteristics of the cardiac signal within the second portion of the characteristic P-wave sensing window, the signal characteristics including zero crossings of the first derivative signal and amplitudes of the second derivative signal corresponding to the determined zero crossings, and detect the P-wave based on the first and the second set of signal characteristics.

11. The medical device of claim 10 , wherein the processor is further configured to determine a maximum amplitude of the determined amplitudes of the second derivative signal within the first portion, and compare the amplitudes of the second derivative signal within the first portion, and compare the amplitudes of the second derivative signal within the second portion to an amplitude threshold, wherein the amplitude threshold is determined based on the determined maximum amplitude of the second derivative signal within the first portion.

12. The medical device of claim 11 , wherein the amplitude threshold comprises a multiple of the maximum amplitude of the second derivative signal within the first portion.

13. The medical device of claim 11 , wherein the processor is configured to determine a number of times the determined amplitudes of the second derivative signal within the second portion are greater than the amplitude threshold, and determine the P-wave based on the determined number of times.

14. The medical device of claim 13 , wherein the processor is configured to determine an RR-interval associated with one of the one or more determined R-waves, determine a relative change associated with the RR-interval, compare the determined RR-interval to an interval threshold and the determined relative change to a change threshold, and confirming the determined R-wave, wherein the P-wave sensing window is determined in response to the confirmed R-wave.

15. The medical device of claim 10 , wherein the processor is configured to determine a maximum amplitude of the determined amplitudes of the second derivative signal within the first portion, determine a maximum amplitude threshold based on the determined maximum amplitude of the second derivative signal within the first portion, determine a min

Assignees

• Medtronic Inc

Inventors

• Sarkar Shantanu
• Hansen Daniel L
• Neitzell Grant A

Classifications

• A61N1/3987

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

• A61N1/36507

  controlled by gradient or slope of the heart potential · CPC title

• A61N1/395

  for treating atrial fibrillation · CPC title

• A61N1/36592

  controlled by the heart rate variability · CPC title

• A61N1/3624 Primary

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