Use and Abuse of Direct Current Shock

Abstract

Direct current (DC) shock is probably the most effective method to terminate various supraventricular as well as ventricular tachyarrhythmias except those induced by digitalis. DC shock is often a life-saving measure in terminating ventricular tachycardia, flutter, and fibrillation. On the other hand, DC shock is not only ineffective in terminating digitalis-induced tachyarrhythmias, but it can also induce new cardiac arrhythmias, particularly ventricular tachycardia or fibrillation, and have a fatal outcome. The indications for DC shock can be divided into 2 major categories; namely, the treatment of acute tachyarrhythmias and elective cardioversion for chronic atrial fibrillation and flutter. About 90% of cases of atrial fibrillation are successfully converted to sinus rhythm, whereas 95–97% of cases of ventricular tachycardia can be terminated by DC shock. DC shock is most effective in terminating atrial flutter with relatively small energy discharges.