Tracking preference as unusual trigger of pacemaker-mediated tachycardia in a resynchronization device.

A 59-year-old woman with a history of congestive heart failure, who previously received a biventricular cardioverter-defibrillator was admitted with dyspnea and peripheral edema. She was noted on telemetry to have multiple self-terminated episodes of rapid ventricular pacing, consistent with pacemaker-mediated tachycardia. All episodes started after three consecutive ventricular extrasystoles. "Tracking preference" algorithm, designed to maintain atrial-tracked biventricular pacing in CRT devices, resulted turned on. It affected minimum PVARP and resulted the trigger for pacemaker mediated tachycardia.