Automatic sensing vector selection for morphology-based capture verification

• US 20050137638A1
• Filed: 12/22/2003
• Published: 06/23/2005
• Est. Priority Date: 12/22/2003
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Yonce, David J., Ternes, David
• Granted Patent: US 7,412,287 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36842 Multi-site stimulation in the same chamber
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold

Abstract

A system and method for verifying capture of the heart by one or more pacing pulses using an electrogram morphology-based technique. Capture is determined by comparing an evoked response electrogram recorded during a paced cycle with a template waveform representing a paced cycle in which capture is achieved. The comparison is facilitated and made more accurate by selecting a sensing vector in which an evoked response electrogram in which no capture occurs is most dissimilar to the template.

Claims

1. A method for verifying capture by a cardiac pacemaker, comprising:

recording an evoked response electrogram during a paced cardiac cycle;

comparing the waveform of the evoked response electrogram with a template waveform representing capture;

determining that capture has occurred during the paced cardiac cycle if the degree of similarity between the evoked response and template waveforms is above a specified threshold; and

,

selecting a sensing vector for generating the evoked response and template waveforms by;

     1) comparing electrograms generated by capturing and non-capturing pacing pulses for a plurality of different sensing vectors,

     2) selecting the sensing vector which results in the greatest degree of dissimilarity between the electrograms generated by the capturing and non-capturing pacing pulses.

2. The method of claim 1 wherein the pacemaker delivers biventricular pacing pulses during the paced cycle and further comprising:

cross-correlating the waveform of the evoked response electrogram with a template waveform representing biventricular capture;

determining that capture has occurred during the paced cardiac cycle if the correlation between the evoked response and template waveforms is a above a specified threshold;

cross-correlating an electrogram generated during biventricular capture with an electrogram generated when biventricular capture is not achieved for the plurality of sensing vectors; and

,

selecting the sensing vector for generating the evoked response and template waveforms as that sensing vector for which the electrograms generated during biventricular capture and no biventricular capture are the least correlated.

3. The method of claim 2 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during right ventricle-only capture, referred to as an RV-only capture template.

4. The method of claim 2 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during left ventricle-only capture.

5. The method of claim 2 further comprising:

for each of the plurality of sensing vectors, generating an electrogram during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram during right ventricle-only capture, referred to as the RV-only capture template; and

,

selecting the optimum sensing vector as the one in which the BiV capture template is least correlated to whichever of the LV-only and RV-only capture templates is most similar to the BiV capture template.

6. The method of claim 2 wherein the plurality of sensing vectors are formed by selecting particular switchable electrodes of the pacemaker for recording electrograms.

7. The method of claim 2 wherein the plurality of sensing vectors are formed by selecting particular leads of a surface ECG apparatus for recording electrograms.

8. The method of claim 2 wherein the sensing vector is selected prior to performing a threshold test for determining an appropriate pacing pulse energy for the pacemaker.

9. The method of claim 2 wherein the sensing vector is selected during a template acquisition routine in which a template representing biventricular capture is generated.

27. The method of claim 2 further comprising:

for each of the plurality of sensing vectors, generating an electrogram during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram during right ventricle-only capture, referred to as the RV-only capture template;

selecting an optimum sensing vector for verifying LV capture as the one in which the BiV capture template is least correlated to the RV-only capture template; and

,

selecting an optimum sensing vector for verifying RV capture as the one in which the BiV capture template is least correlated to the LV-only capture template.

10. A system for verifying capture by an implantable cardiac pacemaker, comprising:

an implantable cardiac pacemaker;

an external programmer in communication with the pacemaker via a wireless telemetry link; and

,

wherein the external programmer is configured to;

store an evoked response electrogram recorded during a paced cardiac cycle;

compare the waveform of the evoked response electrogram with a template waveform representing capture;

determine that capture has occurred during the paced cardiac cycle if the degree of similarity between the evoked response and template waveforms is a above a specified threshold; and

,

select a sensing vector for generating the evoked response and template waveforms by;

     1) comparing electrograms generated by capturing and non-capturing pacing pulses for a plurality of different sensing vectors,

     2) selecting the sensing vector which results in the greatest degree of dissimilarity between the electrograms generated by the capturing and non-capturing pacing pulses.

11. The system of claim 10 wherein the pacemaker delivers biventricular pacing pulses during the paced cycle and wherein the external programmer is configured to:

cross-correlate the waveform of the evoked response electrogram with a template waveform representing biventricular capture;

determine that capture has occurred during the paced cardiac cycle if the correlation between the evoked response and template waveforms is a above a specified threshold;

cross-correlate an electrogram generated during biventricular capture with an electrogram generated when biventricular capture is not achieved for the plurality of sensing vectors; and

,

select the sensing vector for generating the evoked response and template waveforms as that sensing vector for which the electrograms generated during biventricular capture and no biventricular capture are the least correlated.

12. The system of claim 11 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during right ventricle-only capture.

13. The system of claim 11 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during left ventricle-only capture.

14. The system of claim 11 wherein the external programmer is further configured to:

for each of the plurality of sensing vectors, store an electrogram generated during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram generated during right ventricle-only capture, referred to as the RV-only capture template; and

,

select the optimum sensing vector as the one in which the BiV capture template is least correlated to whichever of the LV-only and RV-only capture templates is most similar to the BiV capture template.

15. The system of claim 11 wherein the evoked response electrogram is an electrogram transmitted to the external programmer by the pacemaker and further wherein the plurality of sensing vectors are formed by selecting particular switchable electrodes for incorporating into a sensing channel of the pacemaker for recording electrograms.

16. The system of claim 11 wherein the plurality of sensing vectors are formed by selecting particular leads of a surface ECG apparatus incorporated into the external programmer for recording electrograms.

17. The system of claim 11 wherein the external programmer is configured to automatically select the sensing vector prior to performing a threshold test for determining an appropriate pacing pulse energy for the pacemaker.

18. The system of claim 11 wherein the external programmer is configured to automatically select the sensing vector during a template acquisition routine in which a template representing biventricular capture is generated.

28. The system of claim 11 wherein the external programmer is further configured to:

for each of the plurality of sensing vectors, store an electrogram generated during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram generated during right ventricle-only capture, referred to as the RV-only capture template;

selecting an optimum sensing vector for verifying LV capture as the one in which the BiV capture template is least correlated to the RV-only capture template; and

,

selecting an optimum sensing vector for verifying RV capture as the one in which the BiV capture template is least correlated to the LV-only capture template.

19. An implantable cardiac pacemaker, comprising:

a pacing channel for delivering pacing pulses;

a sensing channel for generating electrogram signals;

a controller for controlling the operation of the pacemaker, wherein the controller is configured to;

store an evoked response electrogram recorded during a paced cardiac cycle;

compare the waveform of the evoked response electrogram with a template waveform representing capture;

determine that capture has occurred during the paced cardiac cycle if the degree of similarity between the evoked response and template waveforms is a above a specified threshold; and

,

select a sensing vector for generating the evoked response and template waveforms by;

     1) comparing electrograms generated by capturing and non-capturing pacing pulses for a plurality of different sensing vectors,

     2) selecting the sensing vector which results in the greatest degree of dissimilarity between the electrograms generated by the capturing and non-capturing pacing pulses.

20. The pacemaker of claim 19 wherein the pacemaker delivers biventricular pacing pulses during the paced cycle and wherein the controller is configured to:

cross-correlate the waveform of the evoked response electrogram with a template waveform representing biventricular capture;

determine that capture has occurred during the paced cardiac cycle if the correlation between the evoked response and template waveforms is a above a specified threshold;

cross-correlate an electrogram generated during biventricular capture with an electrogram generated when biventricular capture is not achieved for the plurality of sensing vectors; and

,

select the sensing vector for generating the evoked response and template waveforms as that sensing vector for which the electrograms generated during biventricular capture and no biventricular capture are the least correlated.

21. The pacemaker of claim 20 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during right ventricle-only capture.

22. The pacemaker of claim 20 wherein the electrogram generated when biventricular capture is not achieved for purposes of sensing vector selection is an electrogram generated during left ventricle-only capture.

23. The pacemaker of claim 20 wherein the controller is further configured to:

for each of the plurality of sensing vectors, store an electrogram generated during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram generated during right ventricle-only capture, referred to as the RV-only capture template; and

,

select the optimum sensing vector as the one in which the BiV capture template is least correlated to whichever of the LV-only and RV-only capture templates is most similar to the BiV capture template.

24. The pacemaker of claim 20 wherein the plurality of sensing vectors are formed by selecting particular switchable electrodes for incorporating into a sensing channel of the pacemaker for recording electrograms.

25. The pacemaker of claim 20 wherein the controller is configured to automatically select the sensing vector prior to performing a threshold test for determining an appropriate pacing pulse energy for the pacemaker.

26. The pacemaker of claim 20 wherein the controller is configured to automatically select the sensing vector during a template acquisition routine in which a template representing biventricular capture is generated.

29. The pacemaker of claim 20 wherein the controller is further configured to:

for each of the plurality of sensing vectors, store an electrogram generated during left ventricle-only capture, referred to as the LV-only capture template, and an electrogram generated during right ventricle-only capture, referred to as the RV-only capture template;

select an optimum sensing vector for verifying LV capture as the one in which the BiV capture template is least correlated to the RV-only capture template; and

,

select an optimum sensing vector for verifying RV capture as the one in which the BiV capture template is least correlated to the LV-only capture template.