An Experimental Study of Transvenous Defibrillation Using a Coronary Sinus Catheter

The efficacy of a transvenous defibrillating system, utilizing bipolar right ventricular and coronary sinus catheters was evaluated in 14 normal mongrel dogs. Two groups of seven animals each were studied. During all shocks, the right ventricular apex electrode served as the anode. In both groups, defibrillation was performed using the proximal pole of the right ventricular catheter (superior vena cava), as the cathode served as a control (configuration A). In group 1, a coronary sinus cathode (configuration B) was compared to control. The mean energy at which 50% or more of the shocks were successful was similar for configuration B (20.7 ± 7.9 joules) and for configuration A (18.8 ± 9.4 joules). In group 2, the superior vena cava and coronary sinus electrodes served as a common cathode (configuration C). Mean defibrillation energy at which 50% or more of the shocks was successful was 21.4 ± 9.0 joules for configuration C and 27.1 ± 9.5 joules for configuration A (P < 0.01). Leading edge voltage was similar for all three configurations, hut shock duration was longer for configuration A (11.3 ± 2.8 msec) than configuration B (6.6 ± 1.8 msec) or C (6.1 ± 1.5; P < 0.05). Nonsustained ventricular tachycardia and transient heart block were common, but no damage to the coronary sinus was noted despite the delivery of up to 38 shocks. Conclusions: (1) With the catheter system used, coronary sinus to right ventricular apex defibrillation system offered no advantages over a superior vena cava to right ventricular apex system; (2) A three‐electrode system with the high right atrium and coronary sinus serving as the common cathode reduced defibrillation thresholds significantly without any severe short‐term adverse consequences; and (3) Improvements in catheter design may make a coronary sinus catheter part of a feasible transvenous defibrillating system.