Voltage dip in pacemaker battery supply: a new cause of pacemaker mediated tachycardia

A new cause of pacemaker mediated tachycardia was observed in a patient equipped with a Vitatron Quintech 931 DDD pacemaker. In this type of pacemaker the microprocessor is switched off during the atrial refractory period. Beyond the recommended replacement time, the internal resistance of the battery may increase to such an extent that switching on and off the microprocessor may cause voltage dips. Those voltage dips are erroneously interpreted as P waves by the atrial sensing amplifier, which may cause self-triggering of the pacemaker and initiate a pacemaker mediated tachycardia.