Ideal atrial lead positioning to detect retrograde atrial depolarization by digitization and slope analysis of the atrial electrogram.

In 10 patients with intact retrograde (V-A) conduction (mean retrograde conduction time 296 +/- 45 msec), bipolar atrial electrograms were recorded simultaneously from three atrial sites (high right atrium [HRA], low right atrium [LRA], and right atrial appendage [RAA]) during sinus rhythm (anterograde electrogram) and paced ventricular rhythm (retrograde electrogram). Atrial electrograms were digitized and analyzed by a special feature detection program which uses sequential slew-rate changes to discriminate different analogue signals. In all patients, it was possible to distinguish anterograde and retrograde atrial depolarizations using the analogue or digital signal recorded from one and usually two [HRA and RAA] lead sites. Digital signal recognition was machine-based and fully automatic, and could be applied to the prevention of pacemaker-mediated tachycardia if incorporated into future microprocessor-based pulse generators.