Pacemaker-mediated tachycardia is caused by:

B. Sensing of retrograde atrial activation.

DISCUSSION: Pacemaker-mediated tachycardia occurs in the setting of intact ventriculoatrial conduction. Typically, premature ventricular contractions may be conducted retrogradely through the AV conduction system and cause retrograde activation of the atrium. If this retrograde atrial activation occurs after completion of the programmed pacemaker ventriculoatrial refractory period, the atrial event is sensed by the DDD pacemaker and evokes a paced ventricular event that may cause further VA conduction. If each ventricularly paced event results in atrial activation sensed by the pacemaker, pacemaker-mediated tachycardia will be generated.