Electrical cardioversion (defibrillation) for a fast heart rate

Treatment Overview

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, or NSR). The shock is given through metal paddles or patches applied to the outside of the chest wall. Cardioversion is often used as an emergency procedure to correct a fast heart rhythm that is causing low blood pressure, chest pain, or heart failure. Also, it is used in nonurgent situations to convert atrial fibrillation to normal heart rhythm.

The electric shock given during cardioversion is thousands of times stronger than the electric current generated by a pacemaker and can cause the muscles in the body to contract violently. 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 for about 30 minutes. If atrial fibrillation is also present, medicines to prevent blood clots may be given before the procedure and for several months after. 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.

Why It Is Done

Cardioversion is often used as an emergency procedure to correct a fast heart rhythm that is causing low blood pressure, chest pain, or heart failure. Also, it is used in nonurgent situations to convert atrial fibrillation 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.

Risks

In the case of atrial fibrillation of recent onset, there is a small risk that cardioversion will cause a blood clot to dislodge from the left atrium and cause a stroke. Drugs to help prevent clots from forming (anticoagulants) are given before and after the procedure to help reduce this risk. If no blood clot is found inside the left atrium, cardioversion can be done without giving anticoagulants.

In some cases of atrial fibrillation, a type of echocardiogram called a transesophageal echocardiogram may be done to look for blood clots in the left atrium. A transesophageal echocardiogram provides clearer pictures of your heart than a regular echocardiogram.

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.

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Author:	Robin Parks, MS	Last Updated: September 17, 2008
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
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