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Basic Facts

  • Electrical cardioversion is a brief, outpatient procedure in which synchronized, low-voltage electrical shocks are administered to the heart.
  • The shocks treat heart rhythm disturbances, such as atrial fibrillation and atrial flutter, by restoring regular rhythm.
  • Cardioversion is typically quite effective, but rarely cures the abnormal heart rhythm.
Cardioversion is a procedure in which synchronized, low-voltage electrical shocks are administered to the heart to correct an abnormal rhythm, also called an arrhythmia. These shocks may be delivered by placing a device inside (internal) or outside (external) the body. The external type of cardioversion is called electric cardioversion, and involves placing a defibrillator, a small machine with paddles and electrodes, on the patient's chest. Electrical cardioversion is performed to correct abnormal heartbeats in non-emergency ("elective") situations, while internal cardioversion using an implantable cardioverter defibrillator (ICD) is part of cardiopulmonary resuscitation (CPR) during an emergency.


Cardioversion may be used before or after other treatment methods, and is indicated in patients who have heart conditions involving an abnormal rhythm. These conditions include:
  • Atrial fibrillation;
  • Atrial flutter;
  • Ventricular tachycardia, an abnormally fast heartbeat of more than 100 beats per minute that originates in one of the ventricles; and
  • Ventricular fibrillation, an abnormal, non-coordinated heart rhythm originating in one of the ventricles.

In most cases, patients must undergo anticoagulation -- administration of anti-clotting drugs such as heparin and warfarin (Coumadin) -- before cardioversion. Although the physician will provide specific pre-procedure instructions to the patients, typically patients are asked to refrain from eating or drinking within 8 hours of the cardioversion procedure. Medications should still be taken on the day before and the day of the procedure, but with only a small sip of water.


Patients with a rapid, abnormal heart rhythm are eligible for cardioversion. Certain conditions may preclude patients from being eligible. These include:
  • Sinus tachycardia, a rapid heartbeat caused by the sinus node; and
  • Multifocal tachycardia, a rapid heartbeat caused by too many electrical signals from the atria.

Patients who have had an arrhythmia for longer than one year and those who are not taking an anticoagulant medication before cardioversion are at greater risk for complications. Compromised kidney or liver function as well as the presence of other heart conditions such as heart failure or abnormal valves may increase risk as well.


A nurse will give the patient anesthesia through an intravenous (IV) line to eliminate pain and induce sleep. Men may have their chest hair shaved, and electrocardiogram (ECG) patches will be placed on the chest and sometimes the back as well so that the health professionals can monitor the patient's heartbeat during the procedure. Adhesive cardioversion pads will then be placed firmly on the chest. They will automatically discharge a specific amount of electric current (lasting a few seconds) to the heart. In most cases, this will be repeated a few times to restore a regular rhythm.


Afterward, the patient's physician may perform another ECG to ensure the procedure was successful. Results and next steps will be discussed and the patient will be moved to a recovery area.


Complications are rare but may include:
  • Blood clots;
  • Allergic reaction to sedative or medications;
  • Fluid in the lungs;
  • Heart attack; and
  • Stroke.
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