Electrical Cardioversion and Defibrillation

Electrical cardioversion is the delivery of an electric shock to the heart to terminate an abnormal rhythm and allow the heart to resume its normal rhythm. During the procedure, paddles or patches are placed on the chest wall over the heart and the shock is delivered through the chest wall. The shock causes all the heart cells to fire at the same time so that the abnormal circuit is deactivated for a short period of time. Usually, the sinus node will resume its activity first so that normal sinus rhythm continues. Cardioversion is used in urgent situations to stop all life-threatening tachycardias; cardioversion of ventricular fibrillation to sinus rhythm is called defibrillation. Cardioversion or defibrillation may also be used to terminate supraventricular tachycardias such as atrial flutter or atrial fibrillation. The principle of cardioversion and defibrillation forms the basis for the implantable cardioverter-defibrillator.