Since the introduction of closed chest synchronized DC shock treatment for atrial fibrillation by Lown in 1962 (Lown, Amarasingham, and Newman, 1962a; Lown et al., 1962b) many thousands of patients have undergone this treatment. Complications have occurred on occasion. Arrhythmias, some fatal, have been reported by Ross (1964), Morris et al. (1964), Killip (1963), and Turner and Towers (1965). ...