Prevalence of retrograde conduction in heart block after DDD pacemaker implantation

Abstract

Electrophysiologic studies were performed before DDD pacemaker implantation in 50 patients with symptomatic heart block. The patients were separated into 2 groups. Group I consisted of patients with intact retrograde conduction and group II consisted of patients with blocked retrograde conduction. After pacemaker implantation, postventricular atrial refractory periods in patients in group I were programmed at 50 to 100 ms, in excess of the retrograde conduction times measured during electrophysiologic studies. In group II patients, postventricular atrial refractory periods were routinely programmed at 300 ms. During follow-up, patients visited the outpatient clinic at 3-month intervals for noninvasive assessment of the prevalence of retrograde conduction, and to test the inducibility of pacemaker-mediated tachycardias. The mean follow-up of group I (15 patients) was 27 ± 10 months, whereas the mean follow-up of group II (35 patients) was 19 ± 9 months. The mean number of noninvasive tests performed during follow-up was 8 ± 3 per patient for group I and 5 ±3 per patient for group II. in group I, retrograde conduction remained intact in 12 patients (p < 0.01). In 29 of 31 patients in group II, retrograde conduction remained absent (p < 0.01). In 4 patients in group II, chronic atrial fibrillation occurred during followup. Chronic atrial fibrillation did not occur in any patient in group I. During serial electrophysiologic testing, no pacemaker-mediated tachycardias could be induced in any patient in group I or II. These results suggest that electrophysiologic studies performed before pacemaker implantation reliably predict the prevalence of retrograde conduction during follow-up of patients with symptomatic heart block and that adjusted atrial refractory periods of the pulse generator at implantation prevent the induction of pacemaker-mediated tachycardias during serial electrophysiologic testing.