Assessment of electrical conversion of supraventricular arrhythmiasPresented at Symposium of the Royal College of Physicians of Ireland and the American College of Physicians in Dublin, Eire, on 18 September, 1971.

Abstract

Summary Direct current shock therapy in 244 cases of atrial fibrillation, fifty cases of paroxysmal supraventricular tachycardia, and eighteen cases of atrial flutter has been assessed. The administration of intravenous diazepam (Valium) allowed direct current shock therapy without general anaesthesia and tracheal intubation. Seventy percent of cases of atrial fibrillation, 96% of cases of paroxysmal supraventricular tachycardia, and 94% of cases of atrial flutter reverted to sinus rhythm. The 190 patients first treated were followed up after the attempt at conversion until relapse of the arrhythmia or for a minimum of 2 years. The best results were obtained in arrhythmia of thyrotoxic aetiology. In patients with ischaemic/hypertensive heart disease and rheumatic heart disease the results were disappointing. The success rate with direct current shock therapy is inversely related to the cardiothoracic index, and with increase in heart size there is also deterioration in the long-term results. Only one of the patients who had a cardiothoracic index of more than 55% remained in sinus rhythm at the end of 2 years. The success rate decreases with increasing duration of the preceding arrhythmia, particularly when it had been present for more than 1 year, and the stability of the attained sinus rhythm also decreases with increasing duration of the preceding arrhythmia. Direct current shock therapy is the method of choice in most cases of atrial flutter. Direct current shock therapy is seldom indicated in paroxysmal supraventricular tachycardia except in cases with underlying serious heart disease. Direct current shock therapy is contra-indicated in digitalis-induced arrhythmias.