Early Experience with an Implantable Cardioverter

Abstract
We tested the efficacy and safety of a fully programmable cardioverter weighing 95 g, in terminating sustained ventricular tachycardia. The device was implanted transvenously under local anesthesia in seven patients. On command from a programmer or automatically, the cardioverter delivered shocks through a lead inserted to the apex of the right ventricle. It also served as a demand ventricular pacemaker and could perform programmed ventricular stimulation or overdrive pacing. Cardioversion of ventricular tachycardia required less than 0.5 J (mean) and was well tolerated by the patients, who were awake and not sedated. In one patient, a shock terminated ventricular tachycardia with the device in the automatic mode but produced atrial fibrillation with a rapid ventricular response that was intermittently recognized as ventricular tachycardia, triggering additional shocks. One such shock in the ST segment produced ventricular fibrillation that was terminated transthoracically in the emergency room, without residual impairment.