Method and apparatus for atrial arrhythmia episode detection

Patent metadata

Field	Value
Publication number	US-9603543-B2
Application number	US-201514695111-A
Country	US
Kind code	B2
Filing date	Apr 24, 2015
Priority date	Feb 18, 2015
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

A method and implantable medical device for determining an atrial arrhythmia event that includes sensing a cardiac signal, determining an atrial arrhythmia score for identifying the arrhythmia event in response to the sensed cardiac signal, determining a sensing window in response to the sensed cardiac signal, the 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, determining whether the sensed cardiac signal within the first portion and within the second portion corresponds to a P-wave in response to the determined signal characteristics, determining whether a signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied, determining whether to update the arrhythmia score in response to the determined P-wave and the determined signal to noise ratio, and determining whether to delivery an arrhythmia therapy in response to the updated arrhythmia score.

First claim

The invention claimed is:

1. A method of determining an atrial arrhythmia event in an implantable medical device, comprising:
sensing a cardiac signal;
determining an atrial arrhythmia score for identifying the arrhythmia event in response to the sensed cardiac signal;
determining a sensing window in response to the sensed cardiac signal, the sensing window having a first portion and a second portion;
determining a second derivative signal of the sensed cardiac signal within the first portion and the second portion of the sensing window;
determining signal characteristics of the sensed cardiac signal within the first portion and within the second portion;
determining whether the sensed cardiac signal within the first portion and within the second portion corresponds to a P-wave in response to the determined signal characteristics;
determining whether a signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied based on amplitudes of the second derivative signal;
determining whether to update the arrhythmia score in response to the determined P-wave and the determined signal to noise ratio; and
determining whether to deliver an arrhythmia therapy in response to the updated arrhythmia score.

2. The method of claim 1 , wherein determining whether the signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied based on amplitudes of the second derivative signal comprises:
determining a first maximum amplitude of the second derivative signal within the first portion and a second maximum amplitude of the second derivative signal within the second portion of the sensing window;
comparing the first maximum amplitude with the second maximum amplitude; and
determining whether the signal to noise ratio is satisfied in response to the comparing.

3. The method of claim 2 , wherein determining whether the signal to noise ratio is satisfied in response to the comparing comprises determining that the signal to noise ratio is satisfied when the second maximum amplitude is greater than the first maximum amplitude by a predetermined amplitude variation threshold.

4. The method of claim 3 , wherein determining whether the signal to noise ratio is satisfied in response to the comparing comprises determining that the signal to noise ratio is satisfied when the second minimum amplitude is less than the first minimum amplitude by a predetermined amplitude variation threshold.

5. The method of claim 3 , wherein the amplitude variation threshold is greater than four times the maximum amplitude of the second derivative signal within the first portion of the sensing window.

6. The method of claim 1 , wherein determining whether the signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied based on amplitudes of the second derivative signal comprises:
determining a first minimum amplitude of the second derivative signal within the first portion and a second minimum amplitude of the second derivative signal within the second portion of the sensing window;
comparing the first minimum amplitude with the second minimum amplitude; and
determining whether the signal to noise ratio is satisfied in response to the comparing.

7. The method of claim 1 , wherein determining whether the signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied based on amplitudes of the second derivative signal comprises:
determining a first maximum amplitude of the second derivative signal within the first portion and a second maximum amplitude of the second derivative signal within the second portion of the sensing window;
determining a first minimum amplitude of the second derivative signal within the first portion and a second minimum amplitude of the second derivative signal within the second portion of the sensing window;
comparing the first maximum amplitude with the second maximum amplitude and the first minimum amplitude with the second minimum amplitude; and
determining that the signal to noise ratio is satisfied in response to one of the second maximum amplitude being greater than the first maximum amplitude by a predetermined amplitude variation threshold or the second minimum amplitude being less than the first minimum amplitude by the amplitude variation threshold.

8. The method of claim 1 , further comprising determining, in response to the signal to noise ratio not being satisfied, whether the sensed cardiac signal within the first portion and within the second portion of the sensing window corresponds to one of a flutter event and a noise event.

9. The method of claim 8 , further comprising updating the arrhythmia score in response to the sensed cardiac signal within the first portion and within the second portion of the sensing window not corresponding to one of a flutter event and a noise event and the signal to noise ratio not being satisfied.

10. The method of claim 1 , wherein the atrial arrhythmia event comprises one of an atrial tachycardia event and an atrial fibrillation event, the method further comprising increasing, in response to the sensed cardiac signal within the first portion and within the second portion corresponding to a P-wave, a P-wave evidence counter for atrial fibrillation by a first predetermined amount and increasing a P-wave evidence counter for atrial tachycardia by a second predetermined amount not equal to the first predetermined amount.

11. The method of claim 10 , wherein the medical device comprises a subcutaneous device.

12. An implantable medical device for determining an atrial arrhythmia event, comprising:
a plurality of electrodes sensing the cardiac signal; and
a processor configured to determine an atrial arrhythmia score for identifying the arrhythmia event in response to the sensed cardiac signal, determine a sensing window in response to the sensed cardiac signal, the sensing window having a first portion and a second portion, determine a second derivative signal of the sensed cardiac signal within the first portion and the second portion of the sensing window, determine signal characteristics of the sensed cardiac signal within the first portion and within the second portion, determine whether the sensed cardiac signal within the first portion and within the second portion corresponds to a P-wave in response to the determined signal characteristics, determine whether a signal to noise ratio of the sensed cardiac signal within the first portion and the second portion of the sensing window is satisfied based on amplitudes of the second derivative signal, determine whether to update the arrhythmia score in response to the determined P-wave and the determined signal to noise ratio, and determine whether to deliver an arrhythmia therapy in response to the updated arrhythmia score.

13. The medical device of claim 12 , wherein the processor is further configured to determine a first maximum amplitude of the second derivative signal within the first portion and a second maximum amplitude of the second derivative signal within the second portion of the sensing window, compare the first maximum amplitude with the second maximum amplitude, and determine whether the signal to noise ratio is satisfied in response to the comparing.

14. The medical device of claim 13 , wherein the processor is configured to determine that the signal to noise ratio is satisfied when the second maximum amplitude is greater than the first maximum amplitude

Assignees

• Medtronic Inc

Inventors

• Sarkar Shantanu
• Hansen Daniel L
• Neitzell Grant A
• Reiland Jerry D
• Wyszynski Ryan

Classifications

• A61N1/36592

  controlled by the heart rate variability · CPC title

• A61B5/686

  Permanently implanted devices, e.g. pacemakers, other stimulators, biochips (A61B5/6861 takes precedence) · CPC title

• A61N1/395

  for treating atrial fibrillation · CPC title

• A61N1/36507

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

• A61N1/3624 Primary

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