Cardioversion uses an external defibrillator to return your heart to a normal rhythm.

First you are given a sedative. Then a doctor places paddles or patches either on your chest or on your chest and back. They send an electric current to your heart. This resets your heart rhythm. The rhythm is more likely to return to normal and stay there if you also take antiarrhythmic medicines before and after this treatment.

Taking antiarrhythmic medicines alone—without electrical cardioversion—is another way to get back your normal heart rhythm. But they don't work as well as cardioversion. And they can have serious side effects.

The success of electrical cardioversion depends on how long you have had atrial fibrillation and what is causing it. Cardioversion is less successful if you have had atrial fibrillation for longer than 1 year.

After this treatment, about 9 out of 10 people get back into a normal heart rhythm right away. But for many people, atrial fibrillation returns. About 3 to 5 out of 10 people still have a normal heart rhythm a year after cardioversion.¹ Normal rhythm may last less than a day or for weeks or months. It depends on your other health problems.

Staying in a normal rhythm is more likely when the cause of your rhythm problem is not heart disease. But for most people, atrial fibrillation is caused by heart disease and is very likely to return.

If your atrial fibrillation returns, you may be able to have cardioversion again. But if the problem comes back quickly (within a week or so), having the treatment yet again is less likely to help you.

If you take antiarrhythmic medicines too, they can help you stay in a normal rhythm longer.

Having a stroke is the most serious risk. Cardioversion may dislodge a blood clot in your heart. This can cause a stroke. But you can lower this risk quite a bit by taking certain steps:

• If your atrial fibrillation has lasted for more than 48 hours, your doctor may have you take anticoagulants, or blood thinners, several weeks before cardioversion.
• Your doctor may use a test called transesophageal echocardiogram to see if you have a clot in your heart. If you don't, you won't have to take a blood thinner first.
• Your doctor may have you take a blood thinner for a few weeks after the treatment.

Cardioversion also has other risks:

• You can get a small area of burn on your skin where the paddles are placed.
• Antiarrhythmic medicines used before and after this treatment may cause a deadly irregular heartbeat. The cardioversion itself may also cause this.
• You could have a reaction to the sedative given to you before the procedure. But harmful reactions are rare.
• The procedure may not work. You may need more cardioversion or other treatment.

If you choose not to try cardioversion, you still will be at risk for problems from atrial fibrillation, such as:

• A fast or irregular heartbeat, chest pain, or shortness of breath, especially during physical activity or when you feel stressed.
• Tiring easily, feeling weak or confused, feeling dizzy, or fainting.

If your symptoms don't bother you, your doctor may have you take medicines to slow your heart rate.

You will still probably need to take an anticoagulant (also called a blood thinner) to lower your risk of stroke. But these medicines raise your risk of a serious bleeding problem. If you take warfarin (Coumadin), you'll need to have your blood tested often to make sure the medicine is working safely.

Your doctor may recommend this treatment if:

• Your atrial fibrillation is not related to another heart problem.
• You have had only one episode of atrial fibrillation.
• You have symptoms that bother you a lot, such as shortness of breath.