The prevention of pacemaker mediated tachycardias in double-chamber pacing.

In 32 consecutive patients selected for physiological pacing assessment of ventriculo-atrial conduction (VAC) was performed, with incremental pacing and ventricular extrastimulation. This is easily done intraoperatively; VA conduction was present in 13 patients. When sinus node disease accompanied antegrade block retrograde conduction never occurred. The mean VA time was 241 +/- 42 ms (Mean +/- standard deviation). One patient developed pacemaker mediated tachycardia while negative findings were present; it was induced by coupled ventricular premature beats. Two patients of the group with VAC had to be reprogrammed in DVI because of disabling symptoms. Pacemaker tachycardia usually develops within the first hours after implantation. The mechanisms and the ways to prevent the tachycardia are discussed.