Cardioversion converts certain types of abnormal heart rhythms to normal rhythms. Abnormal heart rhythms are called arrhythmias. Cardioversion can be accomplished as either an internal or external procedure. In an emergency situation, external cardioversion is performed with a defibrillator.

Non-emergency external cardioversion is usually scheduled on an outpatient basis. The most common type uses carefully timed mild electrical shocks to restore normal heart beat by stopping an arrhythmia. During the procedure, the patient receives general anesthesia or a strong sedative, and does not feel any pain.

Cardioversion is successful in correcting specific arrhythmias, such as atrial fibrillation, that have not improved by medication alone. Some patients may be required to continue antiarrhythmic drugs after the cardioversion procedure.