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 dis- charge 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 alter- nating 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. SUBJECTS AND METHODThere were 75 patients with rheumatic heart disease, 6 with a history of thyrotoxicosis, and 2 with myo- cardial ischmmia.Their ages varied from 25 to 65 with an average of 46-2 years.There were 54 women and 29 men.Four patients had normal exercise tolerance, 67 were in grade 2, and 12 were in grade 3 disability as defined by the New York Heart Association (1953).There were 51 patients who had undergone previous mitral valvotomy, and of these 17 had more than one operation.The average time interval between attempted conversion and the last valvotomy was 2-5 years.The duration of atrial fibrillation varied from 1 month to 16 years with an average of 46 1 months.Quinidine conversion was not attempted in any of these patients immediately before D.C. conversion.Quinidine conversion had, however, been attempted without success in four patients, 4 to 6 years before D.C. shock conversion.D.C. shock was effective in three of the four.A direct current condenser discharge of 2 5 millisecond duration with energy levels between 100-400 watt 128on July 29,