Capture Verification Using An Evoked Response Reference

• US 20100168813A1
• Filed: 03/08/2010
• Published: 07/01/2010
• Est. Priority Date: 12/31/2002
• Status: Active Grant

• Current Assignee: Jaeho Kim, Joseph Bocek
• Original Assignee: Jaeho Kim, Joseph Bocek
• Inventors: Bocek, Joseph, Kim, Jaeho
• Granted Patent: US 8,027,725 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold

Abstract

A method and system for verifying capture in the heart involves the use of pacing artifact templates. One or more pacing artifact templates characterizing a post pace artifact signal associated with a particular pace voltage or range of voltages are provided. A pacing artifact template is canceled from a cardiac signal sensed following a pacing pulse. Capture is detected by comparing the pacing artifact canceled cardiac signal to an evoked response reference. Fusion/pseudofusion detection involves determining a correlation between a captured response template and a sensed cardiac signal.

Claims

1. A method of operating a cardiac device to detect capture of a patient'"'"'s heart, comprising:

delivering one or more non-capturing electrical stimulation pulses to a heart;

sensing one or more pacing artifact waveforms respectively associated with the one or more non-capturing electrical stimulation pulses;

forming a pacing artifact template using the pacing artifact waveforms;

after forming the pacing artifact template, delivering a subsequent electrical stimulation pulse to the heart;

sensing a cardiac signal following the stimulation pulse;

canceling the pacing artifact template from the sensed cardiac signal to form a pacing artifact template canceled signal;

comparing the pacing artifact cancelled cardiac signal and to an amplitude reference characterizing an amplitude of an evoked response; and

detecting capture of the heart based on comparison of the pacing artifact cancelled cardiac signal and the amplitude reference.

2. The method of claim 1, wherein the amplitude reference is a peak-to-peak amplitude reference.

3. The method of claim 1, wherein forming the pacing artifact template comprises estimating the pacing artifact template as an exponential function.

4. The method of claim 1, further comprising:

comparing the cardiac signal to a captured response template; and

detecting fusion/pseudofusion based on comparison of the pacing artifact template canceled signal to the captured response template.

5. The method of claim 1, wherein forming the pacing artifact template comprises forming a plurality of pacing artifact templates, each pacing artifact template of the plurality of pacing artifact template associated with a particular pacing pulse amplitude.

6. The method of claim 1, wherein forming the pacing artifact template comprises forming a plurality of pacing artifact templates, each pacing artifact template of the plurality of pacing artifact templates associated with a range of pacing pulse amplitudes.

7. The method of claim 1, wherein forming the pacing artifact template using the pacing artifact waveforms comprises:

averaging the pacing artifact waveforms to form an average pacing artifact waveform; and

estimating a time constant from the average pacing artifact waveform.

8. The method of claim 1, further comprising periodically updating the pacing artifact template.

9. The method of claim 1, further comprising updating the amplitude reference after detecting a captured beat.

10. A cardiac therapy device, comprising:

cardiac electrodes configured to electrically couple to a heart;

a pulse generator configured to deliver pacing pulses to the heart via the cardiac electrodes;

sense circuitry configured to sense cardiac electrical signals following the pacing pulses;

template circuitry configured to form at least one pacing artifact template using one or more noncaptured cardiac electrical signals sensed following one or more pacing pulses that did not capture the heart;

a capture detector configured to cancel the pacing artifact template from a cardiac signal sensed following a pacing pulse, to compare the pacing artifact cancelled cardiac signal to an amplitude reference characterizing an amplitude of an evoked response, and to detect capture of the heart based on comparison of the pacing artifact cancelled cardiac signal and the amplitude reference.

11. The cardiac therapy device of claim 10, wherein the template circuitry is configured to form multiple pacing artifact templates, each pacing artifact template corresponding to a range of pace pulse amplitudes.

12. The cardiac therapy device of claim 10, wherein the template circuitry is configured to form a captured response template.

13. The cardiac therapy device of claim 12, wherein the capture detector is configured to compare the cardiac signal to the captured response template and to detect fusion/pseudofusion based on comparison of the cardiac signal to the captured response template.

14. The cardiac therapy device of claim 10, wherein the pacing artifact template is characterized by an exponential function.

15. The cardiac therapy device of claim 10, wherein the template circuitry is configured to determine an time constant from an average of the noncaptured cardiac signals and to use the time constant to form the pacing artifact template.

16. The cardiac therapy device of claim 10, wherein the amplitude reference comprises a peak to peak amplitude reference.

17. The cardiac therapy device of claim 10, wherein the one or more noncaptured cardiac electrical signals are sensed, respectively, following one or more pacing pulses delivered while cardiac tissue is refractory.

18. A cardiac therapy device, comprising:

cardiac electrodes configured to electrically couple to a heart;

a pulse generator configured to deliver pacing pulses to the heart via the cardiac electrodes;

sense circuitry configured to sense cardiac electrical signals following the pacing pulses;

means for canceling a pacing artifact template from a cardiac signal sensed following a pacing pulse to form a pacing artifact cancelled cardiac signal, comparing the pacing artifact cancelled cardiac signal to an amplitude reference characterizing an amplitude of an evoked response, and detecting capture of the heart based on comparison of the pacing artifact cancelled cardiac signal and the amplitude reference.

19. The cardiac therapy device of claim 18, further comprising means for forming a pacing artifact template.

20. The cardiac therapy device of claim 18, wherein the amplitude reference comprises a peak to peak amplitude reference which has been updated using the peak to peak amplitude of a pacing artifact cancelled cardiac signal of a captured beat.