Pacing system with physiologically timed ventricular pacing

摘要

There is provided an improved pacing system and method which monitors when the ventricle has become appropriately filled with blood and controls the delivery of each ventricular pace pulse to substantially coincide with desired ventricular filling, e.g., when the chamber has substantially filled. By this technique, the desired time for delivering the ventricular pace pulse is determined on a beat-by- beat basis, providing an improved physiologically optimum mode of pacing. The physiologically ventricular pacing technique of this invention is applicable either to a single chamber pacemaker, or to a dual chamber pacemaker, and in either case enables the important improvement of delivering the pace pulse at the most physiologically appropriate time. In a first embodiment, the moment when the ventricle has substantially filled with blood is determined by monitoring impedance variations which vary inversely with ventricular volume, such that filling of the ventricle corresponds to the time when the impedance waveform bottoms out, or reaches a minimum level. Other sensor arrangements which provide information as to the state of or rate of change of ventricular volume can likewise be used. The invention enables a single lead-single chamber pacemaker which achieves effective synchrony with atrial contractions, or a dual chamber pacemaker which does not require programming of an AV interval.