Pacemaker system and method with improved detection of end of retrograde conduction

The dual chamber pacemaker system places the pacemaker in an asynchronous mode when retrograde conduction is present. The onset of retrograde conduction is detected, and also monitored on a cycle-by-cycle basis to determine, the end of retrograde conduction. The detection of end of retrograde conduction is accomplished by two operative algorithms, i.e., a first algorithm which is executed at the time of any atrial sense and a second algorithm which is executed at the time of each ventricular event. Following an atrial sense, the pacemaker checks to see whether the just concluded VA interval conforms to predetermined RC interval criteria, and if not, immediately switches the pacemaker out of the RC mode and into a synchronous tracking mode. Following each ventricular event while the pacemaker is in the RC mode, the pacemaker monitors a predetermined class of special events and determines end of RC upon detection of a pattern of such special events.