Direct-current Shock in Treatment of Drug-resistant Cardiac Arrhythmias.

ment of ventricular fibrillation at the time of cardiac operations, and has proved successful at other times (McDonald et al., 1963). Lown et al. (1962b) have described the use of directcurrent shock both experimentally and in the treatment of patients with atrial and ventricular arrhythmias (Lown et al., 1962a). The use of direct current enables the shock to be applied at a precise moment in the cardiac cycle, since the charge is activated by the R wave of the electrocardiogram and timed to occur synchronously with it. Thus undesirable-effects such as ventricular fibrillation are avoided ; ventricular fibrillation may theoretically occur if the shock enters the cardiac cycle during the phase of ventricular repolarization. Lown's " cardioverter,"l the unit that was used in this work, consists of a capacitor of 16 microfarads which is charged by a variable D.C. transformer and discharges over 2.5 milliseconds across an inductance coil, and the resistance of the body, to give an underdamped impulse.