Ventriculo-atrial Conduction in Man

Transvenous electrodes were placed in the right atrium and ventricle of 50 patients with heart disease and arrhythmias. The ventricles were paced at several rates, each in excess of the sino-atrial rate. An atrial electrogram and surface electrocardiogram were recorded simultaneously in each patient; utilizing strict criteria, the incidence with which 1:1 ventriculo-atrial conduction (VAC) could be elicited in these patients was assessed. These patients were divided into two groups-26 patients with normal A-V conduction comprised group 1, and 24 patients with prolonged A-V conduction, group 2. VAC was demonstrated in 89% of group 1 patients but in only 8% of the group 2 patients. The difference in the incidence of 1:1 VAC between the two groups was statistically significant ( P < 0.01). The presence or absence of 1:1 VAC could not be related to type of heart disease, medication, presence of acute myocardial infarction, or presence of intraventricular conduction defect. Altering the paced ventricular rate or introducing stimulated ventricular premature depolarization in group 1 patients could produce any degree of VAC impairment. During such maneuvers, ventricular reciprocal beats (ventricular echoes) and ventricular reciprocal rhythms were observed.