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.

Who Needs Cardioversion?

You may need cardioversion if you have an arrhythmia that's causing troublesome symptoms. These symptoms may include dizziness, shortness of breath, extreme fatigue (tiredness), and chest discomfort.

Atrial fibrillation (A-tre-al fi-bri-LA-shun), or AF, is the most common type of arrhythmia treated with cardioversion. In AF, the electrical signals travel through the upper chambers of your heart (the atria) in a fast and disorganized way. This causes the atria to quiver instead of contract.

Atrial flutter, which is similar to AF, also may be treated with cardioversion. In atrial flutter, the electrical signals travel through the atria in a fast, but regular, rhythm.

Less commonly, you may have cardioversion to treat a rapid heart rhythm in the lower chambers of your heart.

You may need cardioversion on an emergency basis if your symptoms are severe. However, you usually schedule this procedure in advance.

Cardioversion may not be right for you if you have other heart conditions as well as an arrhythmia. Talk to your doctor about whether cardioversion is an option for you.

What To Expect Before Cardioversion

You usually can't have any food or drinks for about 12 hours before the cardioversion (as your doctor advises).

You're at increased risk for dangerous blood clots during and after a cardioversion. This is because the procedure can dislodge blood clots that may have formed due to an arrhythmia. Your doctor may prescribe anticlotting medicine to prevent these clots. People often take this medicine for several weeks before the procedure and for several weeks to months after the procedure.

To find out whether you need anticlotting medicine, your doctor may have you undergo a transesophageal echocardiogram (TEE) before the cardioversion. A TEE is a special type of ultrasound. An ultrasound is a test that uses sound waves to look at the organs and structures in the body.

You will be given medicine to make you sleep during the TEE. A special wand that transmits sound waves is put on the end of a tube. The tube is put down your throat into your esophagus (the passage from your mouth to your stomach). The tube is placed close to your heart, and the sound waves create pictures of your heart. Your doctor will look at these pictures to see whether you have any blood clots.

The TEE will be scheduled for the same time as the cardioversion or just before the procedure. If blood clots are found, your cardioversion may be put off for a few weeks. During this time, you will take anticlotting medicine.

Even if no blood clots are found, you will be given anticlotting medicine through a vein during the cardioversion. You also will take medicine after the procedure to prevent blood clots.

Before a cardioversion, you're given medicine to make you sleep through the procedure. This medicine can affect your awareness when you wake up. You will need to arrange for someone to drive you home after the procedure.

What To Expect During Cardioversion

A nurse or technician will stick soft patches, called electrodes, on your chest and possibly on your back. Some shaving may be needed to get the patches to stick to your skin.

These patches are attached to a cardioversion machine. This machine records your heart's electrical activity. The machine also sends low-energy shocks through the patches to restore a normal heart rhythm.

Your nurse will use a needle to insert an intravenous (IV) line into a vein in your arm. Through this line, the doctor or nurse will give you medicine to make you fall asleep. While you're asleep, a cardiologist (heart specialist) will give one or more low-energy electrical shocks to your heart. You won't feel any pain from the shocks because of the medicine used to make you sleep.

Your heart rhythm and blood pressure will be closely watched during the procedure for any signs of complications.

Cardioversion

The illustration shows a typical setup for a nonemergency cardioversion. Figure A shows an irregular heart rhythm recording (before the cardioversion). Figure B shows a normal heart rhythm recording (after the cardioversion). Figure C shows the patient lying in bed with cardioversion pads attached to his body. The doctor closely watches the procedure.

Cardioversion takes just a few minutes. However, you will likely be in the hospital for a few hours due to the prep time and monitoring after the procedure.

What To Expect After Cardioversion

You will be closely watched for an hour or so after the procedure for any signs of complications. Your doctor or nurse will let you know when you can go home.

You may feel drowsy for several hours after the cardioversion because of the medicine used to make you sleep. You shouldn't drive or operate heavy machinery the day of the procedure. You will need to arrange for someone to drive you home from the hospital. Until the medicine wears off, it also may affect your awareness and ability to make decisions.

You may have some redness or soreness on your chest where the electrodes were placed. This may last for a few days after the procedure. You also may have slight bruising or soreness at the site where the intravenous (IV) line was inserted.

You will take medicine for several weeks to months after the procedure to prevent blood clots. During this time, you also may take medicine to prevent repeat arrhythmias.

What Are the Risks of Cardioversion?

Cardioversion can sometimes worsen arrhythmias. Rarely, it can cause life-threatening arrhythmias. These irregular heartbeats will occur within minutes of the procedure. They're treated right away with electrical shocks or medicines, so they usually don't cause serious problems.

Rarely, cardioversion can cause stroke or other complications due to blood clots in the heart traveling to other organs or tissues. The risk of this happening is less than 5 percent if you take anticlotting drugs before and after the procedure.

Key Points

• Cardioversion is a procedure used to restore a fast or irregular heartbeat (an arrhythmia) to a normal rhythm.
• Cardioversion is done two ways: using an electrical procedure or using medicines. This article discusses electrical cardioversion. For this procedure, low-energy shocks are given to your heart to trigger a normal rhythm.
• Cardioversion isn't the same as defibrillation. Defibrillation gives high-energy shocks to the heart. It's used to restore normal heartbeats during life-threatening situations, such as cardiac arrest.
• You may need cardioversion if you have an arrhythmia that's causing troublesome symptoms. These symptoms may include dizziness, shortness of breath, extreme fatigue (tiredness), and chest discomfort.
• Atrial fibrillation is the most common type of arrhythmia treated with cardioversion.
• You may need cardioversion on an emergency basis if your symptoms are severe. However, you usually schedule this procedure in advance.
• You're at greater risk for dangerous blood clots during and after a cardioversion. This is because the procedure can dislodge blood clots that may have formed due to an arrhythmia. Your doctor may prescribe medicine both before and after the procedure to prevent these blood clots from causing complications, such as stroke.
• Before a cardioversion, you're given medicine to make you sleep through the procedure. While you're asleep, a cardiologist will give one or more low-energy electrical shocks to your heart to trigger a normal heartbeat. You won't feel any pain from the shocks due to the medicine used to make you sleep.
• Cardioversion takes just a few minutes. However, you will likely be in the hospital for a few hours due to the prep time and monitoring after the procedure.
• You will be watched closely for an hour or so after the procedure for any signs of complications. You may feel drowsy for several hours after cardioversion because of the medicine used to make you sleep. You should arrange for someone to drive you home after the procedure.
• Cardioversion has some risks. It can worsen arrhythmias. Rarely the procedure can cause stroke or other complications due to blood clots in the heart traveling to other organs or tissues. However, serious complications are rare.
• Cardioversion successfully restores normal heart rhythms in more than 75 percent of people who have the procedure.

Links to Other Information About Cardioversion

NHLBI Resources

• Arrhythmias (Diseases and Conditions Index)
• Atrial Fibrillation (Diseases and Conditions Index)

Non-NHLBI Resources

• Cardioversion (MedlinePlus)

Clinical Trials

• Current Research (ClinicalTrials.gov)