What Is Cardioversion?

Cardioversion (KAR-de-o-VER-shun) is a procedure used to restore a fast or irregular heartbeat to a normal rhythm. A fast or irregular heartbeat is called an arrhythmia (ah-RITH-me-ah).

Arrhythmias can prevent your heart from pumping enough blood to your body. They also can raise your risk for stroke, heart attack, or sudden cardiac arrest.

Overview

To understand arrhythmias, it helps to understand how the heart works. Your heart has an internal electrical system that controls the rate and rhythm of your heartbeat. With each heartbeat, an electrical signal spreads from the top of your heart to the bottom.

As it travels, the signal causes your heart to contract and pump blood. The process repeats with each new heartbeat. (For more information on the heart's electrical system and a detailed animation, go to the Diseases and Conditions Index article on How the Heart Works.)

A problem with any part of this process can cause an arrhythmia. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm. Cardioversion is used to correct fast or irregular heartbeats.

Cardioversion is done two ways: using an electrical procedure or using medicines.

For the electrical procedure, low-energy shocks are given to your heart to trigger a normal rhythm. You're temporarily put to sleep before the shocks are given. This type of cardioversion is done in a hospital as an outpatient procedure. This means you can go home after the procedure is done.

Cardioversion also can be done by taking medicines that correct arrhythmias. This type of cardioversion usually is done in the hospital. It also can be done at home or in a doctor's office.

This article only discusses the electrical procedure.

Many doctors prefer to do electrical cardioversions because they work better and are more predictable. It's also easier to find out right away if the procedure worked.

Cardioversion isn't the same as defibrillation (de-fib-ri-LA-shun), although they both involve shocking the heart. Defibrillation gives high-energy shocks to the heart to treat very irregular and severe arrhythmias. Defibrillation is used to restore normal heartbeats during life-threatening situations, such as cardiac arrest.

For more information on defibrillation, see the Diseases and Conditions Index articles on Sudden Cardiac Arrest and Implantable Cardioverter Defibrillator.

Outlook

Cardioversion successfully restores normal heart rhythms in more than 75 percent of people who have the procedure. However, fast or irregular heartbeats can occur again. For this reason, you may need to have more than one cardioversion over time.

The procedure has some risks. For example, it may worsen arrhythmias. However, serious complications are rare.

July 2008