System and method for automatic atrial capture detection and atrial pacing threshold determination

• US 6,389,316 B1
• Filed: 01/11/2000
• Issued: 05/14/2002
• Est. Priority Date: 01/11/2000
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Bornzin, Gene A., Levine, Paul A., Valikai, Kenneth, Sholder, Jason A.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US09/481,085
• Time in Patent Office: 854 Days
• Field of Search: 607/4, 607/8, 607/7, 607/5, 607/9, 607/11, 607/14, 607/17, 607/19, 607/27, 607/28, 607/13
• US Class Current: 607/28
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold
• CPC Class Codes: A61N 1/3714 Atrial capture

Abstract

An implantable dual chamber stimulation device provides a novel detection scheme for automatically detecting atrial capture and performing an atrial pacing threshold assessment. The stimulation device preferably waits until the patient is at or near rest and monitors the patient'"'"'s P-wave activity to determine an detection window where a next P-wave is expected to occur. The stimulation device then delivers an atrial pulse prior to the next detection window, and monitors the window to determine whether a P-wave occurs therein. If a P-wave does not occur, then atrial capture is present, while occurrence of a P-wave indicates absence of atrial capture. If atrial capture is absent, the stimulation device automatically determines an appropriate atrial pacing threshold by monitoring the detection window while adjusting the stimulation pulse energy level. Advantageously, the present invention further employs a “bottom-up” adjusting scheme which starts at a low energy level, below the expected atrial pacing threshold, and increases the energy level until atrial capture is detected, thus saving energy and further avoiding corruption by large polarization signals. The latter feature is compatible with the present detection scheme and conventional evoked response detection schemes. The new atrial pacing threshold is then set at the atrial pulse level at which atrial capture was effectuated plus a predetermined safety margin.

Claims

1. In an implantable stimulation device, wherein the implantable stimulation device is a dual-chamber device operable in an atrial tracking mode and an atrial non-tracking mode, a system for detecting atrial capture and automatically setting an atrial stimulation pulse energy, the system comprising:

sensing means for sensing intrinsic P-waves;

pulse generating means for generating atrial stimulation pulses;

control means, coupled to the sensing means and the pulse generating means, for defining a P-wave detection window based on the sensed P-waves, for triggering the pulse generator to generate atrial stimulation pulses at a predetermined interval prior to the detection window, for detecting non-capture when a P-wave is sensed during the detection window, and for detecting capture when a P-wave is not sensed during the detection window;

wherein the control means further comprises;

means for determining that an atrial capture assessment is needed;

means for switching from the atrial tracking mode to the atrial non-tracking mode when atrial capture assessment is needed; and

means for switching from the atrial non-tracking mode back to the atrial tracking mode when atrial capture is present; and

adjusting means for adjusting atrial stimulation pulse energy until capture is detected as indicated by the detected absence of P-waves in the detection window.

2. The system of claim 1, further comprising:

activity sensing means for generating an activity signal having a magnitude indicative of a patient'"'"'s physical activity level;

means for detecting when the magnitude of the activity signal is less than a predetermined level indicating that the patient is resting; and

wherein the control means includes means for defining the detection window only when the activity signal indicates that the patient is resting.

3. The system of claim 1, wherein the control means further comprises:

means for adjusting stimulation rate so that intrinsic P-waves occur when an atrial capture assessment is needed;

means for determining an intrinsic P—

P interval; and

means for defining the detection window based on a range about the intrinsic P—

P interval.

4. The system of claim 1, wherein the adjusting means further comprises:

means for decreasing the atrial stimulation pulse energy to a predetermined low energy level when atrial capture assessment is needed; and

means for incrementing the atrial stimulation pulse energy by a predetermined amount until P-waves do not occur during the detection window corresponding to the presence of atrial capture.

5. The system of claim 1, wherein the control means further comprises:

means for setting the detection window, wherein the P-waves that are expected to occur during the detection window comprise retrograde P-waves; and

means for detecting non-capture when a retrograde P-wave is sensed during the detection window, and for detecting capture when a retrograde P-wave is not sensed during the detection window.

6. In an implantable stimulation device, a system for detecting atrial capture and automatically setting an atrial stimulation pulse energy, the system comprising:

sensing means for sensing intrinsic P-waves;

pulse generating means for generating atrial stimulation pulses;

control means, coupled to the sensing means and the pulse generating means, for defining a P-wave detection window based on the sensed P-waves, for triggering the pulse generator to generate atrial stimulation pulses at a predetermined interval prior to the detection window, for detecting non-capture when a P-wave is sensed during the detection window, and for detecting capture when a P-wave is not sensed during the detection window;

wherein the control means further comprises;

means for determining that an atrial capture assessment is needed;

means for adjusting stimulation rate so that intrinsic P-waves occur when an atrial capture assessment is needed;

mean for determining an intrinsic P—

P interval; and

means for defining the detection window based on a range about the intrinsic P—

P interval; and

adjusting means for adjusting atrial stimulation pulse energy until capture is detected as indicated by the detected absence of P-waves in the detection window.

7. The system of claim 6, wherein the adjusting means further comprises:

means for decreasing the atrial stimulation pulse energy to a predetermined low energy level when atrial capture assessment is needed; and

means for incrementing the atrial stimulation pulse energy by a predetermined amount until P-waves do not occur during the detection window corresponding to the presence of atrial capture.

8. The system of claim 7, wherein the incrementing means further comprises:

means for incrementing the atrial stimulation pulse energy by a predetermined safety margin.

9. The system of claim 6, wherein the predetermined interval prior to the detection window is between approximately 50 and 100 milliseconds.

10. The system of claim 6, wherein the control means further comprises:

means for setting the detection window approximately equal to a predefined portion of each cardiac cycle, wherein the P-waves that are expected to occur during the detection window comprise retrograde P-waves; and

means for detecting non-capture when a retrograde P-wave is sensed during the detection window, and for detecting capture when a retrograde P-wave is not sensed during the detection window.

11. The system of claim 6, further comprising:

activity sensing means for generating an activity signal having a magnitude indicative of a patient'"'"'s physical activity level;

means for detecting when the magnitude of the activity signal is less than a predetermined level indicating that the patient is resting; and

wherein the control means includes means for defining the detection window only when the activity signal indicates that the patient is resting.

12. The system of claim 6, wherein the implantable stimulation device is a dual-chamber device operable in an atrial tracking mode and an atrial non-tracking mode, wherein the control means further comprises:

means for switching from the atrial tracking mode to the atrial non-tracking mode when atrial capture assessment is needed; and

means for switching from the atrial non-tracking mode back to the atrial tracking mode when atrial capture is present.

13. In an implantable dual-chamber stimulation device, a method for detecting atrial capture and for automatically setting an atrial stimulation level, the method comprising the steps of:

operating in an atrial tracking mode;

determining that an atrial capture assessment is needed;

switching from the atrial tracking mode to an atrial non-tracking mode when atrial capture assessment is needed;

switching from the atrial non-tracking mode back to the atrial tracking mode when atrial capture is present;

sensing intrinsic P-waves;

defining a P-wave detection window based on the sensed P-waves;

generating atrial stimulation pulses at a predetermined interval prior to the detection window;

detecting one of non-capture or capture based on one of the sensing or non-sensing, respectively, of a P-wave during the detection window; and

adjusting atrial stimulation pulse energy when non-capture is detected with each atrial stimulation pulse until atrial capture is detected.

14. The method of claim 13, further comprising the steps of:

generating an activity signal having a magnitude indicative of a physical activity level of the patient;

detecting when the magnitude of the activity signal is less than a predetermined threshold indicating that the patient is approximately at rest; and

defining the detection window only when the activity signal indicates that the patent is approximately at rest.

15. The method of claim 13, the method further comprising the steps of:

adjusting stimulation rate so that intrinsic P-waves occur;

determining an intrinsic P—

P interval based on at least one cardiac cycle; and

defining the detection window which will predict a subsequent intrinsic P-wave.

16. The method of claim 13, wherein the step of adjusting atrial stimulation pulse energy further comprises the steps of:

initially decreasing the atrial stimulation pulse energy to a predetermined low energy level; and

subsequently incrementing the atrial stimulation pulse energy by a predetermined amount until atrial capture is detected.

17. The method of claim 13, further comprising the steps of:

defining the detection window which will predict a retrograde P-wave;

detecting non-capture when a retrograde P-wave is sensed during the detection window; and

detecting capture when a retrograde P-wave is not sensed during the detection window.

18. In an implantable stimulation device, a method for detecting atrial capture and for automatically setting an atrial stimulation level, the method comprising the steps of:

adjusting stimulation rate so that intrinsic P-waves occur;

sensing intrinsic P-waves;

determining an intrinsic P—

P interval based on at least one cardiac cycle;

defining the detection window which will predict a subsequent intrinsic P-wave;

generating atrial stimulation pulses at a predetermined interval prior to the detection window;

detecting one of non-capture or capture based on one of the sensing or non-sensing, respectively, of a P-wave during the detection window; and

adjusting atrial stimulation pulse energy when non-capture is detected with each atrial stimulation pulse until atrial capture is detected.

19. The method of claim 18, wherein the step of adjusting atrial stimulation pulse energy further comprises the steps of:

initially decreasing the atrial stimulation pulse energy to a predetermined low energy level; and

subsequently incrementing the atrial stimulation pulse energy by a predetermined amount until atrial capture is detected.

20. The method of claim 18, further comprising the steps of:

defining the detection window which will predict a retrograde P-wave;

detecting non-capture when a retrograde P-wave is sensed during the detection window; and

detecting capture when a retrograde P-wave is not sensed during the detection window.

21. The method of claim 18, further comprising the steps of:

generating an activity signal having a magnitude indicative of a physical activity level of the patient;

detecting when the magnitude of the activity signal is less than a predetermined threshold indicating that the patient is approximately at rest; and

defining the detection window only when the activity signal indicates that the patient is approximately at rest.

22. The method of claim 18, wherein the implantable stimulation device is a dual-chamber device, the method further comprising the steps of:

operating in an atrial tracking mode;

determining that an atrial capture assessment is needed;

switching from the atrial tracking mode to an atrial non-tracking mode when atrial capture assessment is needed; and

switching from the atrial non-tracking mode back to the atrial tracking mode when atrial capture is present.