Dual-chamber implantable pacemaker and method of operating same for automatically setting the pacemaker's AV interval as a function of a natural measured conduction time

• US 5,741,308 A
• Filed: 05/15/1995
• Issued: 04/21/1998
• Est. Priority Date: 11/13/1992
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Sholder, Jason A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/440,599
• Time in Patent Office: 1,072 Days
• Field of Search: 607/9, 607/14
• US Class Current: 607/9
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/3682 with a variable atrioventricular delay

Abstract

A dual-chamber implantable pacemaker automatically sets its AV or PV interval to a value that is a function of the measured natural conduction time, or AR interval, of a user of the pacemaker. The AR interval is determined on a regular basis, thereby permitting the AV or PV interval set by the pacemaker to adaptively change with any changes in the AR interval. The AV or PV interval is set to a value that is a prescribed amount Δ less than or greater than the measured AR interval. The measured AR interval is typically averaged, or otherwise determined or estimated, based on measurements of several cardiac cycles.

Claims

1. A method of operating a dual-chamber implantable pacemaker, the pacemaker having sensing means for sensing atrial and ventricular activity, generating means for generating atrial and ventricular stimulation pulses, and timing means for setting an AV interval that defines the maximum time permitted by the pacemaker after atrial activity before a ventricular stimulation pulse (V-pulse) is generated, and wherein sensed atrial activity comprises a natural atrial depolarization (P-wave) and sensed ventricular activity comprises a natural ventricular depolarization (R-wave),the method comprising:

(a) sensing P-waves and R-waves with the sensing means;

(b) generating atrial and ventricular stimulation pulses with the generating means for maintaining a specified cardiac rhythm;

(c) determining an AR interval as the time interval between atrial activity and a sensed R-wave, where atrial activity comprises either a sensed P-wave or the generation of an atrial stimulation pulse (A-pulse) by the generating means, whichever occurs first in a given cardiac cycle; and

(d) setting the AV interval of the pacemaker to be equal to the determined AR interval ±

pb, where pb is a time increment ranging from 1 to 100 msec.

2. The method of claim 1 wherein step (a) comprises determining an average AR interval over k cardiac cycles, where k is an integer between 2 and 1024, and wherein step (b) comprises setting the AV interval to be equal to the average AR interval ±

Δ

.

3. The method of claim 1 wherein step (c) comprises (1) defining a cardiac cycle;

(2) sensing whether an R-wave occurs in the defined cardiac cycle;

(3) using as the determined AR interval the AR interval of the defined cardiac cycle when an R-wave occurs therein, (4) in the event an R-wave does not occur in the defined cardiac cycle, defining a subsequent cardiac cycle as one wherein an R-wave does occur, and (5) measuring an AR interval of the subsequent cardiac cycle as the determined AR interval.

4. The method of claim 3 wherein the step of defining the subsequent cardiac cycle comprises sensing whether an R-wave occurs during each defined cardiac cycle, waiting for at least x consecutive cardiac cycles without an R-wave having been sensed, and then monitoring each cardiac cycle thereafter until an R-wave is sensed, where x is an integer from 4 to 512, the first cardiac cycle during which an R-wave is sensed after waiting at least x cardiac cycles comprising the subsequent cardiac cycle.

5. The method of claim 1 wherein the pacemaker further has a VA interval that, in sequential combination with the AV interval defines the duration of an A-to-A interval, or pacing cycle, and wherein variations in the determined AR interval cause corresponding variations in the AV interval, and wherein the method further comprises:

(e) setting a VA interval of the pacemaker to a value that compensates for the variations in the AV interval in order to assure that the A-to-A interval does not change.

6. A method of stimulating cardiac tissue using an implanted dual-chamber pacemaker, the pacemaker having means for sensing atrial and ventricular events, and means for generating a ventricular stimulation pulse (V-pulse) and delivering the V-pulse to a prescribed ventricular location, said method comprising:

(a) sensing atrial and ventricular events in each cardiac cycle;

(b) determining a natural conduction time of the cardiac tissue by sensing both an atrial event and a natural ventricular event (R-wave) within the same cardiac cycle, and defining the natural conduction time as the time interval between the sensed atrial event and the sensed R-wave; and

(c) generating and delivering the V-pulse to the prescribed ventricular location at a time following a sensed atrial event in each cardiac cycle in which an R-wave is not sensed that is a prescribed amount pb different from the natural conduction time last determined in step (b), whereby the natural conduction time determines when the V-pulse is generated in each cardiac cycle not having a sensed R-wave.

7. The method of claim 6 further including determining the natural conduction time as set forth in step (b) pursuant to a prescribed schedule that comprises determining the natural conduction time after x cardiac cycles have elapsed, wherein x is an integer of from 4 to 512.

8. The method of claim 7 wherein step (b) comprises determining whether an R-wave is sensed or not;

and, if an R-wave is sensed, measuring the duration of an AR interval that begins with an atrial event and ends with the sensed R-wave, and using the AR interval thus measured as the determined natural conduction time; and

;

if an R-wave is not sensed, using the duration of a previously measured AR interval of an immediately-preceding cardiac cycle during which an R-wave was sensed as the determined natural conduction time.

9. The method of claim 8, further including measuring the duration of the AR interval of an immediately preceding cardiac cycle during which an R-wave was sensed as the determined natural conduction time only when x consecutive cardiac cycles have elapsed without sensing an R-wave, where x is an integer between 4 and 512.

10. The method of claim 6, comprising generating and delivering the V-pulse at a delivery time within the cardiac cycle that is a prescribed amount Δ

less than the natural conduction time determined in step (b).

11. The method of claim 6, wherein the pacemaker further includes means for defining a VA interval and means for generating an atrial stimulation pulse (A-pulse) at the conclusion of the VA interval, wherein the VA interval begins upon the occurrence of a ventricular event and terminates upon the occurrence of an atrial event, and wherein the method also includes:

changing the VA interval by an appropriate amount so that the duration between successive A-pulses, comprising an A-to-A interval made up of the interval between an atrial event and the generation of the V-pulse as determined in step (c) plus the VA interval, remains unchanged.

12. The method of claim 11, wherein the appropriate amount by which the VA interval is changed comprises 1 to 100 msec.

13. The method of claim 6 wherein the step of determining the natural conduction time comprises measuring the natural conduction time for at least y cardiac cycles, where y is an integer, and computing an average of the natural conduction time measurements thus made, and using such average natural conduction time as the determined natural conduction time.

14. A dual-chamber pacemaker for controlling ventricular pacing as a function of a natural conduction time of a patient'"'"'s heart, comprising:

an atrial channel comprising means for sensing a natural atrial depolarization (P-wave) and means for generating an atrial stimulation pulse (A-pulse) and delivering the A-pulse to an atrium of the patient'"'"'s heart;

a ventricular channel comprising means for sensing a natural ventricular depolarization (R-wave) and means for generating a ventricular stimulation pulse (V-pulse) and delivering the V-pulse to a ventricle of the patient'"'"'s heart at the conclusion of an AV interval unless an R-wave is sensed during the AV interval;

means for sensing a natural conduction time interval of the patient'"'"'s heart through the atrial and ventricular channels, the natural conduction time interval comprising the time interval within a given cardiac cycle that commences with atrial activity, where atrial activity comprises either a sensed P-wave or a paced A-pulse, whichever occurs first within the given cardiac cycle, and that terminates upon a sensed R-wave; and

timing means for defining the AV interval so that the AV interval commences with atrial activity and terminates at a time within the cardiac cycle that is a function of the natural conduction time.

15. The dual-chamber pacemaker of claim 14, wherein the timing means includes means for defining said AV interval to be equal to the natural conduction time interval ±

Δ

, where Δ

is a specified amount.

16. The dual-chamber pacemaker of claim 15, wherein said timing means further includes:

means for defining a VA time interval that commences with a V-pulse and terminates with atrial activity, and wherein the AV interval plus the VA interval defines a pacing interval for the pacemaker; and

means for altering the VA time interval by an appropriate amount so that the pacing interval remains unchanged.