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Heart Disease Health Center

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Electrical Cardioversion (Defibrillation) for a Fast Heart Rate

Electrical cardioversion is a procedure in which a brief electric shock is given to the heart to reset the heart rhythm back to its normal, regular pattern (normal sinus rhythm). The shock is given through paddles or patches camera.gif applied to the outside of the chest wall.

Usually, the person is sedated. If the person is conscious, medicine is given to control pain and to cause the person to relax to the point of being nearly unconscious during the procedure.

What To Expect After Treatment

After cardioversion, the person's heart rate and blood pressure are monitored.

Additional drugs to help prevent heart rhythm problems from recurring (antiarrhythmic drugs) may also be given before and after the procedure. If antiarrhythmic drugs are not used after cardioversion, the heart may be at greater risk of going back into a fast heart rate.

After cardioversion, you may take a blood thinner, such as warfarin, for a few weeks to prevent dangerous blood clots.

Why It Is Done

Cardioversion is often used as an emergency procedure to stop a fast heart rate that is causing low blood pressure or severe symptoms. These heart rate problems include supraventricular tachycardia and ventricular tachycardia.

Also, it is used in nonurgent situations to convert atrial fibrillation or atrial flutter to normal heart rhythm.

How Well It Works

Electrical cardioversion of the heart is very effective. Most people who receive cardioversion return to normal sinus rhythm immediately after the procedure.1


Risks of the procedure include the following:

  • A blood clot may become dislodged from the heart and cause a stroke. Your doctor will try to decrease this risk by using anticoagulants or other measures.
  • The procedure may not work. Additional cardioversion or other treatment may be needed.
  • Antiarrhythmic medicines used before and after cardioversion or even the cardioversion itself may cause a life-threatening irregular heartbeat.
  • You can have a reaction to the sedative given before the procedure. Harmful reactions are rare.
  • You can get a small area of burn on your skin where the paddles are placed.

What To Think About

Cardioversion is only a temporary fix for a fast heart rate. Medicines (such as beta-blockers and calcium channel blockers or other antiarrhythmic medicines) may be used to keep the heart rate slow when a person has an episode of supraventricular tachycardia (SVT). For long-term treatment and to reduce the chance of having another episode of either SVT or ventricular tachycardia (VT), catheter ablation or medicine can be used.

Complete the special treatment information form (PDF)(What is a PDF document?) to help you understand this treatment.

Related Information


  1. Blomström-Lunqvist C, et al. (2003). ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias-Executive summary: A report of the ACC/AHA/ESC Committee for Practice Guidelines. Circulation, 108(15): 1871-1909.

ByHealthwise Staff
Primary Medical ReviewerRakesh K. Pai, MD, FACC - Cardiology, Electrophysiology
Specialist Medical ReviewerJohn M. Miller, MD, FACC - Cardiology, Electrophysiology

Current as ofMarch 12, 2014

WebMD Medical Reference from Healthwise

Last Updated: March 12, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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