Serial electrophysiologic studies after single chamber atrial pacemaker implantation in patients with symptomatic sinus node dysfunction.

Abstract

After single chamber atrial pacemaker implantation, serial electrophysiologic studies were performed noninvasively at intervals of 3 months over a total period of 3 years in 24 patients with symptomatic sinus node dysfunction. All patients underwent invasive electrophysiologic studies before pacemaker implantation and demonstrated intact anterograde AV conduction. Patients were divided into 2 groups: group I did not require antiarrhythmic drugs during follow-up whereas group 2 received antiarrhythmic drugs. In group I (11 patients) the atrial paced heart rate producing AV Wenckebach phenomenon (AVWHR) remained stable during a mean follow-up of 22 +/- 10 months; with a variability not exceeding 10 beats min-1 with respect to the initial AVWHR obtained during preoperative electrophysiologic study. In group 2 (13 patients) with a mean follow-up of 15 +/- 8 months a mean decrease of AVWHR of 19.2 +/- 17.5 beats min-1 was present between AVWHR before and 3 months after initiation of oral antiarrhythmic drugs (P less than 0.01). During chronic (greater than 3 months) antiarrhythmic drug therapy the variability of the AVWHR never exceeded 10 beats min-1 with respect to the AVWHR obtained 3 months after the initiation of oral drug therapy. Deterioration of anterograde AV conduction during long-term follow-up of patients with symptomatic sinus node dysfunction and intact anterograde AV conduction at the time of pacemaker implantation is a consequence of orally taken antiarrhythmic drugs, rather than a consequence of degeneration of the AV conducting system.