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

• US 6,295,471 B1
• Filed: 01/11/2000
• Issued: 09/25/2001
• 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., Sholder, Jason A., Valikai, Kenneth
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/481,748
• Time in Patent Office: 623 Days
• Field of Search: 607/9, 607/11, 607/27, 607/28
• 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 dual-chamber implantable stimulation 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 energy, the system comprising:

sensing means for sensing P-waves;

pulse generating means for generating atrial and ventricular stimulation pulses;

means for determining that an atrial capture assessment is needed;

control means, coupled to the sensing means, the pulse generating means and the determining means, for switching from the atrial tracking mode to atrial non-tracking mode when atrial capture assessment is needed, for causing the pulse generating means to generate a sequence of atrial stimulation pulses with variable energy levels, for defining a detection window following each of the atrial stimulation pulses, and for detecting atrial capture based on the absence or presence of a sensed P-wave in the detection window.

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

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

3. 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 resting 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.

4. The system of claim 1, wherein:

the sensing means includes means for sensing evoked P-waves; and

the control means includes means for defining the detection window immediately following the atrial stimulation pulse such that atrial capture is defined as the absence of an evoked response in the detection window.

5. The system of claim 1, wherein:

the sensing means includes means for sensing intrinsic P-waves; and

the control means includes means for determining a P-P interval, means for defining the detection window based on the P-P interval, and means for triggering the atrial stimulation pulse prior to the detection window such that non-capture is defined when a P-wave is sensed during the detection window and capture is defined when a P-wave is not sensed during the detection window.

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

means for adjusting stimulation rate so that intrinsic P-waves occur;

means for determining an average intrinsic P-P interval; and

means for defining the detection window based on a range about the average intrinsic P-P interval.

7. 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 magnitude of 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. In an dual-chamber implantable stimulation device operable in an atrial tracking mode and an atrial non-tracking mode, a method for detecting atrial capture and automatically setting an atrial stimulation energy, the method comprising the steps of:

determining that an atrial capture assessment is needed;

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

sensing P-waves;

generating atrial and ventricular stimulation pulses with a pulse generator;

defining a P-wave detection window following each of the atrial stimulation pulses;

detecting atrial capture based on the absence or presence of a sensed P-wave in the detection window; and

causing the pulse generator to generate a sequence of atrial stimulation pulses with variable energy levels until capture is re-established.

9. The method of claim 8, wherein the switching step further comprises the step of:

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

10. The method of claim 8, wherein the defining step further comprises the steps of:

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

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

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

11. The method of claim 8, wherein:

the sensing step includes the step of sensing evoked P-waves; and

the defining step includes the steps of defining the detection window immediately following the atrial stimulation pulse such that atrial capture is defined as the absence of an evoked response in the detection window.

12. The method of claim 8, wherein:

the sensing step includes the steps of sensing intrinsic P-waves and measuring an intrinsic P-P interval; and

the defining step includes the steps of defining the detection window based on the measured P-P interval, and triggering the atrial stimulation pulses prior to the detection window such that non-capture is defined when a P-wave is sensed during the detection window and capture is defined when a P-wave is not sensed during the detection window.

13. The method of claim 12, wherein the defining step further comprises the steps of:

adjusting stimulation rate so that intrinsic P-waves occur;

determining an average intrinsic P-P interval; and

defining the detection window based on a range about the average intrinsic P-P interval.

14. The method of claim 8, wherein the causing step further comprises the steps of:

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

incrementing the magnitude of 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.