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

• US 6,721,601 B1
• Filed: 03/19/2002
• Issued: 04/13/2004
• Est. Priority Date: 01/11/2000
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Levine, Paul A., Sholder, Jason A., Valikai, Kenneth, Bornzin, Gene A.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US10/102,271
• Time in Patent Office: 756 Days
• Field of Search: 607/28, 607/27, 607/14, 607/11, 607/9
• 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 that 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 a 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, a method for detecting atrial capture and for automatically setting an atrial stimulation level, the method comprising:

detecting retrograde P-waves;

defining a detection window for a future retrograde P-wave based on the detected retrograde P-waves;

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

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

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

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

2. The method of claim 1, further comprising:

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 at rest; and

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

3. The method of claim 1, wherein the implantable stimulation device is a dual-chamber device, the method further comprising:

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.

4. The method of claim 1, the method further comprising:

adjusting a stimulation rate so that intrinsic retrograde P-waves occur;

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

5. The method of claim 1, wherein the step of adjusting atrial stimulation pulse energy further comprises:

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.

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;

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

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

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

7. 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 comprises means for defining the retrograde detection window only when the activity signal indicates that the patient is resting.

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

means for determining that an atrial capture assessment is needed;

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

P interval.

9. 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 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.

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

means for determining that an atrial capture assessment is needed;

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.

11. An implantable stimulation device, comprising:

a sensing circuit that senses P-waves;

a timing circuit that sets a detection window corresponding to an expected retrograde P-wave;

a pulse generator that generates atrial stimulation pulses; and

a control circuit, coupled to the sensing circuit, the timing circuit and the pulse generator, that triggers the pulse generator to generate an atrial stimulation pulse at a predetermined interval prior to the detection window, that detects non-capture when a retrograde P-wave is sensed during the detection window, and that detects capture when a retrograde P-wave is not sensed during the detection window, the control circuit being operative to adjust the atrial stimulation pulse energy until capture is detected.

12. The system of claim 11, further comprising:

activity sensor that generates an activity signal having a magnitude indicative of a patient'"'"'s physical activity level;

a detector that detects when the magnitude of the activity signal is less than a predetermined level indicating that the patient is resting; and

wherein the control circuit analyzes the detection window for capture threshold management only when the activity signal indicates that the patient is resting.

13. The system of claim 11, wherein the control circuit is configured to adjust a stimulation rate so that intrinsic P-waves occur when an atrial capture assessment is needed, to determine an intrinsic retrograde P—

P interval, and to define the detection window based on a range about the intrinsic retrograde P—

P interval.

14. The system of claim 11, wherein:

the implantable stimulation device is a dual-chamber device operable in an atrial tracking mode and an atrial non-tracking mode; and

the control means is configured to switch from the atrial tracking mode to the atrial non-tracking mode when atrial capture assessment is needed, and to switch from the atrial non-tracking mode back to the atrial tracking mode when atrial capture is present.

15. The system of claim 11, wherein the control circuit is further configured to determine that an atrial capture assessment is needed, to decrease the atrial stimulation pulse energy to a predetermined low energy level when atrial capture assessment is needed, and to increment 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.