Dynamic overdrive pacing for the suppression of ventricular ectopic activity: long-term application using implantable pacemakers

Overdrive pacing is a commonly used method for terminating tachycardias [2]. Furthermore, overdrive suppression of repetitive Purkinje fibre activity is a well known electrophysiological phenomenon. The so far discussed working mechanisms are shown in Table 1. Dynamic overdrive pacing (DO), which means an overdrive stimulation with varying rate, was incorporated in the DPG 1 (Vitatron) for tachycardia prevention. In order to investigate the reliability of this new pacing mode, we first induced complex ventricular extrasystoles (VES) and ventricular tachycardia by bipolar, epicardial direct current (DC) application in 5 pig hearts (20 to 30 kg) in situ during neuroleptanalgesia (method: 24). During ventricular DO pacing, DC-induced complex VES disappeared and tachycardoas needed significantly higher current strengths to be induced. I some cases, tachycardias could not intiated any more.