New Method for Terminating Cardiac Arrhythmias Use of Synchronized Capacitor Discharge Bernard Lown, M.D., Raghavan Amarasingham, M.B., B.S., and Jose Neuman, M.D., Boston THE ECTOPIC TACHYCARDIAS are currently treated by either vagal stimulation or drugs. The 3 most effective drugs are quinidine, procainamide hydrochloride, and the digitalis glycosides. When the ectopic mechanism drives the ventricles at rates above 160 per minute, cardiac output falls and coronary blood flow is compromised. This is most likely to occur with ventricular tachycardia which constitutes a serious cardiac emergency requiring immediate treatment. Frequently, however, the arrhythmia cannot be terminated promptly. Reversion with drugs generally involves a time-consuming biologic titration. Since it is impossible in any one patient to predict either the effective or the toxic dose, small increments of antiarrhythmic drugs are given at frequent intervals until a therapeutic end point is reached. The interval between doses is determined by the gravity of the