PROGRAMMING A LONG PACED ATRIOVENTRICULAR INTERVAL MAY BE RISKY IN DDDR PACING

In patients with intermittent AV block and dual chamber pacemakers, a long paced AV interval of 200 msec or more can be selected to prolong pulse generator life (by avoiding the ventricular pace output) and to enable a more physiological and hemodynamically superior activation se quence. This case report describes the potential risks of programming a long paced AV interval in a patient with a DDDR pacemaker. T wave pa cing, as described here, can occur if the conducted QRS complex is not sensed because it occurs during the ventricular blanking period (deli very of the atrial stimulus). This can be initiated by the mechanisms that induce apparent and actual P wave undersensing of the conducted Q RS complex. in this case report apparent P wave undersensing and subse quent T wave pacing with ventricular capture (in a patient with interm ittent A V block) occurred frequently during an exercise test done in the DDDR mode with a paced A V interval of zoo msec, according to the clinical evaluation protocol.