US 5,334,220 A · Dual-chamber implantable pacemaker having an adaptive AV interval that prevents ventricular fusion beats and method of operating same

Abstract

A dual-chamber implantable pacemaker automatically adjusts its AV interval so that any ventricular stimulation pulses generated by the pacemaker at the conclusion of the pacemaker-defined AV interval occur at a time in the cardiac cycle that avoids fusion with the natural ventricular depolarization of a patient's heart. The AV interval is set using a search sequence that sets the AV interval value to be on one side or the other of the natural conduction time of the heart, and incrementally changes the AV interval value until it crosses over the natural conduction time interval. The cross-over point is manifest by the occurrence of an R-wave, where an R-wave had previously been absent, or the absence of an R-wave, where an R-wave had previously been present. A final AV interval value is then set as the AV interval value at the cross-over point, adjusted by appending an AV margin thereto. The search sequence is automatically invoked whenever a prescribed search time has elapsed, or whenever the sudden presence or absence of a sensed R-wave indicates a sufficient change in the natural conduction time so as to have crossed over with the existing AV interval. If the search sequence is invoked too frequently, it is automatically suspended for a prescribed suspension period.

Claims23

Dependent claims

An implantable pacemaker comprising:

atrial sensing means for sensing an atrial depolarization (P-wave);
atrial pacing means for generating an atrial stimulation pulse (A-pulse);
ventricular sensing means for sensing a ventricular depolarization (R-wave), and;
ventricular pacing means for generating a ventricular stimulation pulse (V-pulse);
means for storing operating instructions and control parameters;
and
controlling means coupled to said storing means, said atrial and ventricular sensing means and said atrial and ventricular pacing means for coordinating the operation of said atrial and ventricular sensing means, and said atrial and ventricular pacing means, in accordance with said operating instructions and said control parameters, said controlling means comprising:
first timing means for defining an AV interval;
second timing means for defining an atrial escape interval;
third timing means for measuring a conduction time interval, said conduction time interval comprising the time between atrial activity and sensing an R-wave, atrial activity comprising either of sensing a P-wave and generating an A-pulse;
first logic means for triggering said ventricular pacing means at the conclusion of said AV interval only in the event an R-wave is not sensed during said AV interval, said AV interval commencing with said atrial activity;
second logic means for triggering said atrial pacing means at the conclusion of said atrial escape interval only in the event a P-wave is not sensed during said atrial escape interval;
and
adjustment means for automatically adjusting said AV interval to a value that is different than said conduction time interval;
whereby V-pulses that are generated by said pacemaker are generated at a time that is different than said conduction time, thereby avoiding fusion between said V-pulses and said R-waves.

12 more elements

An implantable dual-chamber pacemaker that automatically adjusts its AV interval and avoids fusion between the generation of a ventricular stimulation pulse (V-pulse), at the conclusion of said AV interval, and the occurrence of natural ventricular depolarization, as evidenced by the occurrence of an R-wave, said pacemaker comprising:

means for sensing atrial activity in an atrial channel;
means for sensing an R-wave and generating said V-pulse;
and
first control means for defining said AV interval as the longest time interval the pacemaker will allow from the occurrence of atrial activity until the generation of a V-pulse, the occurrence of an R-wave during said AV interval causing the generation of a V-pulse to be inhibited;
second control means for recognizing a need to adjust said AV interval from its present value to a new value;
third control means for adjusting said AV interval from its present value to an intermediate value, when an adjustment in the AV interval is needed, following a prescribed adjustment sequence;
forth control means for determining when in the adjustment sequence the AV interval crosses over an AR interval, said AR interval comprising the time interval between atrial activity and sensing an R-wave, and thereby representing a measure of the natural conduction time of a heart to which said pacemaker is coupled;
and
fifth control means for setting the new AV value of said pacemaker to a value that is a prescribed difference from said AR interval;
whereby a V-pulse and an R-wave will not occur at the same time, thereby avoiding fusion, even though the AV interval is automatically adjusted when needed.

7 more elements

A method of operating a dual-chamber pacemaker to avoid fusion between a ventricular stimulus (V-pulse) and an R-wave, said pacemaker having means for sensing atrial activity, means for sensing an R-wave and means for generating said V-pulse;

and control means for defining said AV interval as the longest time interval the pacemaker will allow from the occurrence of atrial activity until the generation of a V-pulse, the occurrence of an R-wave during said AV interval causing the generation of a V-pulse to be inhibited;
said method comprising the steps of:
(a) generating an A-pulse in the atrium in the absence of said sensed atrial activity;
(b) adjusting said AV interval from its present value to an adjustment start value;
(c) incrementally adjusting the value of said AV interval from its adjustment start value in a direction back towards said first value in prescribed increments, with each prescribed increment comprising a specified change in the duration of said AV interval in the adjustment direction, and with each adjusted value of said AV interval being used in a specified incremental time period that includes at least one cardiac cycle;
(d) monitoring for ventricular activity during each of said specified incremental time periods, said activity comprising either an R-wave and the presence of a V-pulse;
(e) detecting the approximate duration of an AR interval from the monitoring performed in step (d), said AR interval defining the time period between atrial activity and the occurrence of an R-wave;
(f) setting the final value of said AV interval to be different from the AR interval detected in step (e);
and
(g) generating a V-pulse in the absence of a sensed R-wave during said AV interval;
whereby said AV interval is automatically adjusted to a value that avoids fusion between said V-pulse and said R-wave.

8 more elements

A method of adjusting the AV interval of a dual-chamber pacemaker, said pacemaker including atrial pulse generation means for generating an atrial stimulation pulse (A-pulse), ventricular pulse generation means for generating a ventricular stimulation pulse (V-pulse), atrial sensing means for sensing a natural atrial depolarization (P-wave), ventricular sensing means for sensing a natural ventricular depolarization (R-wave), and control means for controlling said atrial and ventricular pulse generation means in response to timed intervals, including an AV interval, generated by said control means, and in response to said atrial and ventricular sensing means;

said AV interval comprising a pacemaker-defined time period that starts with atrial activity, comprising an A-pulse or a P-wave, whichever occurs first, and ends with the generation of a V-pulse providing an R-wave does not occur prior to the termination of said AV interval;
said method comprising the steps of:
(a) generating an A-pulse in the absence of said sensed atrial activity;
(b) changing said AV interval from its present first value, AV.sub.0, to a prescribed adjustment starting value, AV.sub.1 ;
(c) incrementally adjusting said AV interval from the prescribed adjustment starting value AV.sub.1 back towards the first value AV.sub.0 value in prescribed step sizes;
(d) making a determination after each incremental adjustment of the AV interval in step (c) as to whether an R-wave is thereafter sensed by the ventricular sensing means prior to the termination of the AV interval;
and
(e) stopping the adjustment of said AV interval as soon as the determination made in step (d) indicates a change in said determination, said change comprising one of either:
(1) determining that an R-wave is sensed after the most recent adjustment of the AV interval when an R-wave was not previously sensed prior to the most recent adjustment of the AV interval, and (2) determining that an R-wave is not sensed after the most recent adjustment of the AV interval when an R-wave was previously sensed prior to the most recent adjustment of the AV interval;
(f) generating a V-pulse in the absence of a sensed R-wave during said AV interval;
whereby said AV interval is adaptively changed to a value that is close to, but not the same as, the time period between atrial activity and an R-wave;
whereby fusion between an R-wave and a V-pulse is avoided.

9 more elements

Dependencies are inferred from the claim text.

Dual-chamber implantable pacemaker having an adaptive AV interval that prevents ventricular fusion beats and method of operating same

Life of this patent

Dual-chamber implantable pacemaker having an adaptive AV interval that prevents ventricular fusion beats and method of operating same

Life of this patent

Abstract

Claims23