Cardioversion is a procedure that uses external electric shocks to restore a normal heart rhythm.

Cardioversion is called defibrillation when it is done in an emergency to prevent death due to potentially fatal ventricular arrhythmias that can result in sudden cardiac arrest. Alternatively, your doctor can schedule cardioversion as a way to treat arrhythmias in the upper chambers of your heart called atrial fibrillation. If untreated, atrial fibrillation can increase your risk for stroke and heart failure.

Scheduled cardioversion procedures may be done in a hospital or other health care facility by cardiologists, or doctors who specialize in the heart. While the procedure takes only a few minutes, it requires that you arrive a few hours before the procedure. To prepare, you will be given anesthesia through an intravenous (IV) line in your arm to make you fall asleep, and you will have electrodes placed on your chest and possibly your back. These electrodes will be attached to the cardioversion machine. The machine will record your heart’s electrical activity and send the shocks to your heart. When ready, the doctor will send one or more brief, low-energy shocks to your heart to restore a normal rhythm. You will not feel any pain from the shocks.

You will need to stay for a few hours after your procedure. During this time, your health care team will monitor your heart rhythm and blood pressure closely and watch for complications. You will need a ride home because of the medicines or anesthesia you received. You may have some redness or soreness where the electrodes were placed. You also may have slight bruising where the IV line was inserted in your arm.

Although uncommon, cardioversion has some risks. It can cause or worsen life-threatening arrhythmias that will need to be treated. This procedure can cause blood clots to break away and travel from the heart to other tissues or organs and cause a stroke or other problems. Taking anticlotting medicines before and after cardioversion can reduce this risk.

Your doctor may recommend 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 fih-brih-LA-shun), or AF, is a common type of arrhythmia treated with cardioversion. In AF, the heart's electrical signals travel through the heart's upper chambers (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 might be treated with cardioversion. In atrial flutter, the heart's electrical signals travel through the atria in a fast, but regular rhythm.

Cardioversion sometimes is used to treat rapid heart rhythms in the lower heart chambers (the ventricles).

Cardioversion usually is a scheduled procedure. However, you may need an emergency cardioversion if your symptoms are severe.

For some people who have other heart conditions in addition to arrhythmias, cardioversion might not be the best treatment option. Talk with your doctor about whether cardioversion is an option for you.

Although uncommon, cardioversion does have risks. The procedure can sometimes worsen arrhythmias. Rarely, it can cause life-threatening arrhythmias. These irregular heartbeats are treated with electrical shocks or medicines.

Cardioversion can dislodge blood clots in the heart. These clots can travel to organs and tissues in the body and cause a stroke or other problems. Taking anticlotting medicines before and after cardioversion can reduce this risk.

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

You're at higher risk for dangerous blood clots during and after a cardioversion. The procedure can dislodge blood clots that have formed as the result of an arrhythmia.

Your doctor may prescribe anticlotting medicine to prevent dangerous clots. He or she may recommend that you take this medicine for several weeks before and after the cardioversion procedure.

To find out whether you need anticlotting medicine, you might have transesophageal echocardiography (TEE) before the cardioversion. 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.

TEE involves a flexible tube with a device at its tip that sends sound waves. Your doctor will guide the tube down your throat and into your esophagus (the passage leading from your mouth to your stomach). You’ll be given medicine to make you sleep during the procedure.

Your doctor will place the tube close to your heart, and the sound waves will create pictures of your heart. Your doctor will look at these pictures to see whether you have any blood clots.

The TEE will be done at the same time as the cardioversion or just before the procedure. If your doctor finds blood clots, he or she may delay your cardioversion for a few weeks. During this time, you'll take anticlotting medicine.

Even if no blood clots are found, your doctor may prescribe anticlotting medicine during and after the cardioversion to prevent dangerous blood clots from forming.

Before the cardioversion procedure, you’ll be given medicine to make you sleep. This medicine can affect your awareness when you wake up. So, you'll need to arrange for someone to drive you home after the procedure.

A nurse or technician will stick soft pads called electrodes on your chest and possibly on your back. He or she may need to shave some areas on your skin to get the pads to stick.

The electrodes will be attached to a cardioversion machine. The machine will record your heart's electrical activity and send low-energy shocks through the pads 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, you’ll get medicine that will make you fall asleep.

While you're asleep, a cardiologist (heart specialist) will send one or more low-energy electrical shocks to your heart. You won't feel any pain from the shocks.

Your health care team will closely watch your heart rhythm and blood pressure during the procedure for any signs of complications.

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

Your health care team will closely watch you after the procedure for any signs of complications. Your doctor or nurse will let you know when you can go home. You’ll likely be able to go home the same day as the procedure.

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'll 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.

Your doctor will likely prescribe anticlotting medicine for several weeks after the procedure to prevent blood clots. During this time, you also may take medicine to prevent repeat arrhythmias.