Pacemaker and method of operating same that provides functional atrial cardiac pacing with ventricular support
First Claim
1. A method of operating a dual-chamber electronic pacemaker in a positive AV hysteresis mode, the pacemaker having sensing means for sensing selected events, including the presence of AV conduction and AV block;
- pulse generating means for selectively generating an atrial stimulation pulse (A-pulse) and a ventricular stimulation pulse (V-pulse);
timing means for generating specified time intervals, including an AV interval, which time intervals start upon the sensing of prescribed events by the sensing means or the generation of specified stimulation pulses by the pulse generating means;
control means for controlling the pulse generating means as a function of whether the sensing means senses certain prescribed events during a given time interval generated by the timing means;
the method comprising;
(a) setting the AV interval to a first value;
(b) sensing whether AV conduction is present during the AV interval, and if so, keeping the AV interval set to its first value;
(c) sensing whether AV block is present during the AV interval, and if so, issuing a V-pulse at the conclusion of the AV interval;
(d) shortening the AV interval to a second value, less than the first value, after issuing the V-pulse in step (c);
(e) sensing whether AV block continues after shortening the AV interval to its second value, and if so, keeping the AV interval at its second value;
(f) sensing whether AV conduction is present after shortening the AV interval to its second value, and if so, resetting the AV interval to its first value;
(g) sensing whether a prescribed length of time has elapsed since shortening the AV interval to its second value, and if so, resetting the AV interval to its first value in order to test for the return of AV conduction; and
(h) repeating steps (b) through (g) for as long as the pacemaker is to be operated in the positive AV hysteresis mode;
whereby the AV interval assumes either its first value or its second value as a function of whether AV conduction or AV block is sensed; and
further whereby not more than the prescribed length of time ever elapses without testing for the return of AV conduction.
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Accused Products
Abstract
A special type of AV/PV hysteresis is provided in a dual-chamber pacemaker. A long AV delay is initially provided, thereby affording as much opportunity as possible for natural AV conduction to occur. Such long AV delay is automatically shortened should AV block occur. Periodic scanning for the return of AV conduction (absence of AV block) is performed so that the AV delay can be returned to its long value as soon as possible. In one embodiment, the pacemaker "learns" the natural conduction time (AR interval) of the patient and thereafter uses such learned natural conduction time as a reference against which subsequently measured AR intervals are compared to better distinguish conducted ventricular contractions from ectopic, pathologic, or other nonconducted ventricular contractions (e.g., PVC'"'"'s). If the measured AR interval is approximately the same as the "learned" AR interval, then the R-wave at the conclusion of the measured AR interval is presumed to be a conducted R-wave that signals the return of AV conduction, and the AV delay is lengthened back to its original value. If, on the other hand, the measured AR interval is significantly different than the "learned" natural conduction time, then the R-wave at the conclusion of the measured AR interval is presumed to be a nonconducted R-wave, and the AV delay is kept short. In other embodiments, other techniques are used to distinguish a conducted R-wave from a nonconducted R-wave.
186 Citations
10 Claims
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1. A method of operating a dual-chamber electronic pacemaker in a positive AV hysteresis mode, the pacemaker having sensing means for sensing selected events, including the presence of AV conduction and AV block;
- pulse generating means for selectively generating an atrial stimulation pulse (A-pulse) and a ventricular stimulation pulse (V-pulse);
timing means for generating specified time intervals, including an AV interval, which time intervals start upon the sensing of prescribed events by the sensing means or the generation of specified stimulation pulses by the pulse generating means;
control means for controlling the pulse generating means as a function of whether the sensing means senses certain prescribed events during a given time interval generated by the timing means;
the method comprising;(a) setting the AV interval to a first value; (b) sensing whether AV conduction is present during the AV interval, and if so, keeping the AV interval set to its first value; (c) sensing whether AV block is present during the AV interval, and if so, issuing a V-pulse at the conclusion of the AV interval; (d) shortening the AV interval to a second value, less than the first value, after issuing the V-pulse in step (c); (e) sensing whether AV block continues after shortening the AV interval to its second value, and if so, keeping the AV interval at its second value; (f) sensing whether AV conduction is present after shortening the AV interval to its second value, and if so, resetting the AV interval to its first value; (g) sensing whether a prescribed length of time has elapsed since shortening the AV interval to its second value, and if so, resetting the AV interval to its first value in order to test for the return of AV conduction; and (h) repeating steps (b) through (g) for as long as the pacemaker is to be operated in the positive AV hysteresis mode; whereby the AV interval assumes either its first value or its second value as a function of whether AV conduction or AV block is sensed; and
further whereby not more than the prescribed length of time ever elapses without testing for the return of AV conduction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- pulse generating means for selectively generating an atrial stimulation pulse (A-pulse) and a ventricular stimulation pulse (V-pulse);
Specification