Inhibition of a physiologic pacing system due to its anti-pacemaker-mediated tachycardia mode

Newer programmable DDD pacemakers prevent pacemaker-mediated tachycardia by automatic extension of the atrial refractory period after a detected premature ventricular contraction. We present an example in which the automatic extension of the atrial refractory period resulted in pacemaker inhibition, which should not automatically be assumed to represent pacemaker malfunction. A careful understanding of pacemaker timing intervals may allow for identification and correction of this problem.