Atrial and ventricular capture detection and threshold-seeking pacemaker

• US 5,861,012 A
• Filed: 10/18/1996
• Issued: 01/19/1999
• Est. Priority Date: 08/16/1994
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Stroebel, John C.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US08/732,755
• Time in Patent Office: 823 Days
• Field of Search: 607/28, 607/11, 607/25, 607/27
• US Class Current: 607/28
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• 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

Capture detection and stimulation threshold-measurement methods and apparatus for deriving atrial and ventricular pace pulse (A-pace and V-pace) stimulation energy strength-duration data. In a first atrial and ventricular threshold test regimen for use with patients having intact A-V conduction or first degree AV block, A-pace pulses are delivered at a test escape interval and A-V delay. Atrial loss of capture (ALOC) in response to an A-pace test stimulus is declared by the absence of a detected ventricular depolarization (V-event) in the latter portion of the paced A-V delay interval following the delivery of the A-pace test stimulus. In the ventricular threshold test regimen, a V-pace test stimulus is delivered after a shortened A-V delay. Ventricular loss of capture (VLOC) is declared by the detection of a V-event in the ventricular refractory period of the V-pace test stimulus. In a second algorithm for use in the atrium or ventricle in patients having regular measured sinus rhythm, premature A-pace or V-pace test stimuli are delivered, and the presence of an A-event or V-event at the end of the measured sinus escape interval is declared to be ALOC or VLOC, respectively. A-pace and V-pace test stimuli are repeated to confirm capture declarations at an energy exceeding the LOC test energy. The atrial and ventricular stimulation threshold data derived by varying both pulse amplitude (strength) and width (duration) is stored in memory for telemetry out and analysis and for use in setting the V-pace and A-pace normal pulse width and amplitude used between successive auto-capture tests in order to conserve battery energy.

Claims

1. In a pacemaker pulse generator having a pulse generator for generating and applying pacing pulses to a chamber of the heart to evoke a stimulated depolarization and capture the heart and a sense amplifier for sensing natural depolarizations of the heart, a method of testing for the stimulation threshold energy of the pacing pulses sufficient to capture the heart comprising the steps of:

determining a time interval in which a natural depolarization of the heart would be expected to follow a preceding natural or stimulated depolarization and defining a test window encompassing at least a portion of the time interval;

applying a test pacing pulse at a test energy level to the heart at a point during the determined time interval and prior to an expected natural depolarization following a preceding natural or stimulated depolarization;

operating the sense amplifier during the test window to detect a depolarization of the heart;

declaring capture of the heart by the test pacing pulse if a depolarization of the heart is not sensed in the test window; and

declaring loss of capture of the heart by the test pacing pulse if a depolarization of the heart is sensed in the test window.

7. A pacemaker adapted to execute a method as set forth in claim 1 wherein said method further comprises:

said step of applying a test pacing pulse includes;

activating a routine to deliver said pulse prematurely.

8. A pacemaker as set forth in claim 7 wherein activation of said routine occurs during a test for SNR capture detection routine.

9. A pacemaker as set forth in claim 7 wherein activation of said routine occurs during a test to see if SNR will work routine.

10. A pacemaker as set forth in claim 7 wherein the delivery of said applied test pulse is timed to be from about 30 to 70% of the time from a pair of sequential A1 senses.

2. In a pacemaker pulse generator having an atrial pulse generator for generating and applying atrial pacing pulses to the atrium of the heart to evoke a stimulated depolarization and capture the atrium and a ventricular sense amplifier for sensing natural depolarizations of the ventricle, a method of testing for the stimulation threshold energy of the atrium comprising the steps of:

determining the patient'"'"'s atrial escape interval;

operating said atrial pulse generator to deliver an atrial test stimulus at a test energy to the atrium in said atrial escape interval timed to capture the atrium if the test energy is sufficient to capture the atrium;

setting a paced A-V delay interval;

operating the ventricular sense amplifier during at least a portion of the paced A-V delay interval to sense a depolarization of the ventricle;

declaring capture of the atrium by the atrial test pacing pulse if a depolarization of the ventricle is sensed in the paced A-V delay interval; and

declaring loss of capture of the atrium by the atrial test pacing pulse if a depolarization of the ventricle is not sensed in the paced A-V delay interval.

3. In a pacemaker pulse generator having a pulse generator for generating and applying pacing pulses to the one chamber of the heart to evoke a stimulated depolarization and capture the heart chamber and a sense amplifier for sensing natural depolarizations of the heart chamber, a method of testing for the stimulation threshold energy of the heart chamber comprising the steps of:

determining the heart chamber'"'"'s sinus escape interval;

operating the pulse generator to deliver a test stimulus at a test energy to the heart chamber during said escape interval timed to capture the chamber if the test energy is sufficient to capture;

setting a sense time window;

operating the sense amplifier during the sense window to detect a depolarization of the chamber;

declaring loss of capture of the chamber by the test stimulus if a depolarization of the chamber is sensed in the sense time window; and

declaring capture of the chamber by the test stimulus if a depolarization of the chamber is not sensed in the sense time window.

4. In a pacemaker pulse generator having a pulse generator for generating and applying pacing pulses to a chamber of the heart to evoke a stimulated depolarization and capture the heart and a sense amplifier for sensing natural depolarizations of the heart, apparatus for testing for the stimulation threshold energy of the pacing pulses sufficient to capture the heart comprising:

means for determining a time interval in which a natural depolarization of the heart would be expected to follow a preceding natural or stimulated depolarization and defining a test window encompassing the end of the time interval;

means for operating said pulse generator to apply a test pacing pulse at a test energy level to the heart at a point during the determined time interval and prior to an expected natural depolarization following a preceding natural or stimulated depolarization;

means for operating said sense amplifier during the test window to detect a depolarization of the heart;

means for declaring capture of the heart by the test pacing pulse if a depolarization of the heart is not sensed in the test window; and

means for declaring loss of capture of the heart by the test pacing pulse if a depolarization of the heart is sensed in the test window.

5. In a pacemaker pulse generator having a pulse generator for generating and applying pacing pulses to the one chamber of the heart to evoke a stimulated depolarization and capture the heart chamber and a sense amplifier for sensing natural depolarizations of the heart chamber, apparatus for testing for the stimulation threshold energy of the heart chamber comprising:

means for determining the heart chamber'"'"'s sinus escape interval;

means for operating the pulse generator to deliver a test stimulus at a test energy to the heart chamber during said escape interval timed to capture the chamber if the test energy is sufficient to capture;

means for setting a test time window;

means for operating the sense amplifier during the test window to detect a depolarization of the chamber;

means for declaring loss of capture of the chamber by the test stimulus if a depolarization of the chamber is sensed in the test time window; and

means for declaring capture of the chamber by the test stimulus if a depolarization of the chamber is not sensed in the test time window.

6. In a pacemaker pulse generator having a pulse generator for generating and applying pacing pulses to a chamber of the heart to evoke a stimulated depolarization and capture the heart and a sense amplifier for sensing natural depolarizations of the heart, apparatus for testing for the stimulation threshold energy of the pacing pulses sufficient to capture the heart comprising:

means for determining a time interval in which a natural depolarization of the heart would be expected to follow a preceding natural or stimulated depolarization and defining a test window encompassing the end of the time interval;

means for operating said pulse generator to apply a test pacing pulse at a test energy level to the heart at a point during the determined time interval and prior to an expected natural depolarization following a preceding natural or stimulated depolarization;

means for operating said sense amplifier during the test window to detect a depolarization of the heart;

means for declaring capture of the heart by the test pacing pulse if a depolarization of the heart is not sensed in the test window; and

means for declaring loss of capture of the heart by the test pacing pulse if a depolarization of the heart is sensed in the test window.