Cardiovascular dynamics during coronary sinus, right atrial, and right ventricular pacing

Abstract

Permanent pervenous right atrial pacing has not been widely used to date. The coronary sinus may provide a site from where reliable permanent pacing can be performed so as to preserve atrial contribution in patients with intact A-V conduction who require pacing, as in sinus bradycardia, sinus arrest, and recurrent tachyarrhythmias. To test this hypothesis, 15 individuals, 37 to 70 years old (average 56.6 years), with a variety of heart diseases, but with normal A-V conduction, were studied. After control cardiac index had been obtained, coronary sinus, right atrial pacing, and right ventricular pacing were performed at two levels above the control sinus rate. Mean cardiac index was virtually identical for coronary sinus and right atrial pacing at the first level, 2.38 and 2.37 L./min./M. 2, respectively, and at the second level, 2.45 and 2.42 L./min./M. 2, respectively. During the first level of right ventricular pacing mean cardiac index was 1.87 L./min./M. 2, 21.8 per cent lower than during coronary sinus pacing (p < 0.005) and 21.4 per cent lower than right atrial pacing (p < 0.005). For the second level of right ventricular pacing, the mean cardiac index was 1.88 L./min./M. 2, 23.3 per cent lower than during coronary sinus pacing (p < 0.005) and 22.3 per cent lower than right atrial pacing (p < 0.005). Systemic pressures were similar during right atrial and coronary sinus pacing and lower during right ventricular pacing at both pacing levels. Pulmonary artery pressure was higher during right ventricular pacing at both levels. The coronary sinus provides an area from which the heart can be paced with the hemodynamic advantages of atrial pacing if intact A-V conduction exists.