Various techniques are described for preventing pacemaker mediated
tachycardia (PMT) within biventricular pacing systems and for detecting and terminating PMT should it nevertheless arise. In a first prevention technique,
refractory periods applied to the atrial channel are synchronized to begin with a second of a pair of
ventricular pacing pulses to more effectively prevent T-wave oversensing on the atrial channel. In a second prevention technique, the sensitivity of the atrial channel is reduced during T-
waves also to prevent T-wave oversensing. In a third prevention technique,
template matching is performed on the ventricular channels to prevent T-wave oversensing. In a fourth prevention technique, T-
wave detection windows are applied to both the ventricular and atrial channels subsequent to any paced or sensed events. In a first detection technique, PMT is detected based upon a degree of variation within V-pulse to P-wave pacing intervals. In a second detection technique, PMT is detected based upon a degree variation within
ventricular pacing intervals. In either case, if the degree of variation is too low, indicative of PMT, ventricular
refractory periods are expanded to terminate the PMT.