MODEL RELEASED. Emergency defibrillation. Doctor administering emergency defibrillation to a patient. Defibrillation is used to treat a life-threatening irregular heartbeat (arrhythmia) or in the case of cardiac arrest (stopped heart). The electrode paddles held against the man's chest deliver an electric current to the heart. This restarts the heart in the case of cardiac arrest. In an arrhythmia, it stops the erratic rhythm and allows the heart to restart with a normal one.