Conversion of Atrial Fibrillation by Direct Current Counter Shock.

The adverse effects of atrial fibrillation on the circulation are well known. It reduces cardiac output and stroke volume (Kory and Meneely, 1951; Broch and Muller, 1957), may lead to cardiac dilatation and failure (Phillips and Levine, 1949), and is associated with a high risk of systemic embolization (Sokolow, 1951; Fraser and Turner, 1955). Unfortunately, attempts to restore sinus rhythm with drug therapy are often unsuccessful and carry a definite hazard. Thus the mortality from quinidine conversion of atrial fibrillation still varies from 1 per cent (Yount, Rosenblum, and McMillan, 1952) to 3 per cent (Hay, 1924; Askey, 1946), and morbidity from quinidine toxicity is much higher (Kohn and Levine, 1935; Thompson, 1956; Rokseth and Storstein, 1963). The use of alternating current applied to the chest wall for the abolition of supraventricular arrhythmias was limited by the risk of ventricular fibrillation (Zoll et al., 1956; Paul and Miller, 1962). Gurvich and Yuniev (1947) were the first to draw attention to the effectiveness of capacitor discharge in defibrillating the heart, though the technique was first used by Prevost and Battelli (1899). Their results, however, were not confirmed by Guyton and Satterfield (1951) or Kouwenhoven and Milnor (1954). Lown et al. (1962b) showed that in dogs direct current capacitor discharge was superior to alternating current in abolishing ventricular fibrillation. He also showed that the capacitor discharge of 2-5 millisecond duration, synchronized to avoid the vulnerable period at the apex of the T wave, was effective in the abolition of atrial fibrillation without the risk of ventricular fibrillation (Lown, Amarasingham, and Neuman, 1962a). Further clinical studies by Lown et al. (1963), Killip (1963), and Oram et al. (1963) have confirmed the effectiveness and safety of this procedure. The results of direct current capacitor discharge in attempted conversion of atrial fibrillation in 83 patients are presented here.