Unusual Wenckebach Upper Rate Response of an Atrial‐Based DDD Pacemaker

We describe in this report an unusual form of Wenckebach upper rate response produced by a DDD pulse generator with atrial‐based lower rate timing. The pacemaker maintained the programmed upper and lower rate intervals at the expense of a prolonged atrial paced‐venfricular paced AV interval. This form of upper rate behavior eliminated the longer cycle (containing the unsensed P wave) that occurs at the end of the pacemaker Wenckebach sequence during traditional DDD pacing with ventricular‐based lower rate timing.