Method and system for characterizing a representative cardiac beat using multiple templates

• US 7,529,581 B2
• Filed: 02/27/2007
• Issued: 05/05/2009
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Bocek, Joseph, Kim, Jaeho
• Primary Examiner(s): Layno; Carl H.
• Assistant Examiner(s): MORALES, JON ERIC C
• Application Number:
  US11/711,329
• Publication Number:
  US 20070149889A1
• Time in Patent Office: 798 Days
• Field of Search: 600/515
• US Class Current: 600/515
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

Providing a method and system for characterizing one beat of a patient'"'"'s supraventricular rhythm. A plurality of templates is provided and updated using a plurality of qualified beats. Updating occurs by temporally aligning the shock channel waveforms of the template beats using rate channel fiducial points. The template beats are combined by point-by-point addition of the shock channel waveforms. The resultant updated template characterizes one of the patient'"'"'s supraventricular conducted cardiac beats.

Claims

1. A method of characterizing a patient'"'"'s cardiac rhythm in an implantable device, comprising:

detecting a cardiac beat;

extracting feature timing information from the cardiac beat and each template of a plurality of templates;

temporally aligning the cardiac beat with at least one template of the plurality of templates based on the feature timing information;

selectively updating the plurality of templates using the aligned cardiac beat;

associating a plurality of counters with the plurality of templates, and each time a template is updated incrementing a counter associated with the updated template; and

identifying a particular template of the plurality of templates as representative of the cardiac rhythm.

2. The method of claim 1, wherein detecting the cardiac beat comprises detecting a two channel cardiac beat signal.

3. The method of claim 1, wherein aligning the cardiac beat signal and the at least one template comprises:

extracting a fiducial point of the cardiac beat;

extracting a fidicial point of the at least one template; and

temporally aligning the cardiac beat and the template based on the extracted fiducial points.

4. The method of claim 3, wherein selectively updating the plurality of templates comprises:

extracting features from the aligned cardiac beat having predetermined temporal relationships to the fiducial point of the at least one template; and

updating the at least one template using the cardiac beat if the extracted features are similar to corresponding template features.

5. The method of claim 1, wherein selectively updating the plurality of templates using the aligned cardiac beat comprises:

calculating a feature correlation coefficient for the cardiac beat and a template of the plurality of templates; and

updating the template if the feature correlation coefficient is greater than a predetermined value.

6. The method of claim 1, wherein identifying the particular template comprises identifying the particular template as representative of the cardiac rhythm based on a number of times the particular template is updated.

7. The method of claim 1, wherein identifying the particular template comprises:

identifying the particular template as representative of the cardiac rhythm if the particular template has a highest counter value of the plurality of counters.

8. The method of claim 1, wherein identifying the particular template comprises:

identifying the particular template a representative of the cardiac rhythm if the counter for the particular template reaches a predetermined value before the counters for other templates reach the predetermined value.

9. The method of claim 1, further comprising:

retrieving at least one template of the plurality of templates from memory; and

generating at least one template of the plurality of templates using a previous cardiac beat.

15. The system of claim 1, wherein the control system is configured to identify the particular template as representative of the cardiac rhythm based on a value of a counter associated with the particular template.

16. The system of claim 1, wherein the control system is configured to identify the particular template as representative of the cardiac rhythm if the particular template has a counter value higher than that of the counters associated with other templates.

17. The system of claim 1, wherein the control system is configured to identify the particular template as representative of the cardiac rhythm if a counter associated with the particular template reaches a predetermined value before counters associated with other templates.

10. A body implantable system for characterizing cardiac rhythms, comprising:

a sensing system comprising electrodes electrically coupled to a heart, the sensing system configured to detect a cardiac beat;

a control system coupled to the sensing system, the control system configured to temporally align the cardiac beat with at least one template of a plurality of templates based on feature timing information extracted from the cardiac beat and the templates, selectively update the plurality of templates using the aligned cardiac beat, and identify a particular template of the plurality of templates as representative of the cardiac rhythm; and

counters associated with the plurality of templates, wherein the counters are selectively incremented each time a template is updated.

11. The system of claim 10, further comprising a memory, wherein the control system retrieves at least one template of the plurality of templates from the memory.

12. The system of claim 10, wherein the control system is configured to generate a new template using the cardiac beat if no templates are similar to the cardiac beat.

13. The system of claim 10, wherein:

the feature timing information extracted from the cardiac beat comprises a fiducial point of the cardiac beat; and

the feature timing information extracted from the templates comprises fidicial points of the templates.

14. The system of claim 10, wherein:

the feature timing information extracted from the cardiac beat comprises a peak value of the cardiac beat; and

the feature timing information extracted from the templates comprises peak values of the templates.

18. An implantable cardiac system, comprising:

means for aligning a cardiac beat with each template of a plurality of templates based on feature timing information extracted from the cardiac beat and the templates;

means for selectively updating one or more templates of the plurality of templates using the aligned cardiac beat;

means for associating a plurality of counters with the plurality of templates, and for selectively incrementing the counters each time a template is updated; and

means for identifying a particular template of the selectively updated templates as representative of the cardiac rhythm.

19. The system of claim 18, further comprising:

means for retrieving at least one template of the plurality of templates from memory; and

means for generating at least one template of the plurality of templates using a previous cardiac beat.

20. The system of claim 18, wherein the identifying means identifies the particular template as representative of the cardiac rhythm based on a value of the counter associated with the particular template.