Skip to content

    Heart Disease Health Center

    Font Size

    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.

    Today on WebMD

    x-ray of human heart
    A visual guide.
    atrial fibrillation
    Symptoms and causes.
    heart rate graph
    10 things to never do.
    heart rate
    Get the facts.
    empty football helmet
    red wine
    eating blueberries
    Simple Steps to Lower Cholesterol
    Inside A Heart Attack
    Omega 3 Sources
    Salt Shockers
    lowering blood pressure