[Endocardial cardioversion--a new method for treating recurrent ventricular tachycardia]

The effect of endocardial cardioversion was investigated in 17 patients (aged 26-76 years), ten of them with ventricular tachycardia, either spontaneous or initiated by programmable stimulation. During a total of 14 days of observation there were 33 episodes of spontaneous or induced ventricular tachycardia. A special cardioverter catheter had been placed into the right ventricle and endocardial microshocks were given ranging from 0.05-2.0 J. All patients could feel the shock, but in most instances it was mild to moderate, in only one painful. The tachycardia was slowed in 20% of all microshocks, moderate acceleration occurred in 6%, while in 71% the tachycardia rate remained unchanged. In 7 out of 65 microshocks sinus rhythm occurred spontaneously, after an interval in which the tachycardia slowed. Atrial fibrillation was induced in 6% of cases, but there was no instance of ventricular fibrillation. Reversion directly to sinus rhythm after endocardial cardioversion occurred in 26 of 33 episodes of ventricular tachycardia, while in 7 episodes the tachycardia rate slowed. In no case was it necessary to use external DC cardioversion to terminate a ventricular tachycardia. Threshold values for successful cardioversion of ventricular tachycardia averaged 0.77 (+/- 0.63) J. In one patient, atrial flutter with a relatively high A-V conduction rate was converted into atrial fibrillation by an intra-atrial microshock of 5.0 J. Thus endocardial cardioversion proved effective and safe in terminating ventricular tachycardia, even in patients in whom anti-tachycardic ventricular pacemaker stimulation had failed. The method is apparently not suitable for the conversion of supraventricular tachy-arrhythmias to sinus rhythm.