Permanent transvenous atrial pacing.

Atrial pacing has electrophysiologic and hemodynamic advantages for patients with symptomatic bradyarrhythmias and intact atrioventricular conduction or with certain refractory tachyarrhythmias. Permanent atrial pacing has been achieved in 29 patients followed up for periods of up to 7 years at two institutions. At Sunnybrook Medical Centre, Toronto, 16 patients have had coronary sinus electrodes introduced pervenously using standard bipolar or special unipolar catheters. Initial pacing thresholds were acceptably low (mean, 2.0 mA); chronic thresholds in three patients were similar. At the Toronto General Hospital, 13 patients had endocardial J-electrodes, bipolar or tined unipolar, inserted in the right atrial appendage. Initial thresholds were low (mean, 1.3 mA) and P-wave voltage was adequate (3.4 mV) for pacemakers with standard sensitivity. In both series, conventional R-inhibited, asynchronous or rate-programmable units have been employed. Radiofrequency self-conversion pacemakers were used in three patients. Preliminary His bundle studies were done in 10 patients; the others were tested by rapid atrial pacing during insertion of electrodes. Early and late electrode stability in both series was excellent; one electrode became dislodged from the coronary sinus position and one from the right atrial appendage.