What is atrial fibrillation?

Atrial fibrillation (say "A-tree-uhl fih-bruh-LAY-shun") is an irregular heart rhythm (arrhythmia) that starts in the upper parts (atria) of the heart.

Normally, the heart beats in a strong, steady rhythm. In atrial fibrillation, a problem with the heart’s electrical system causes the atria to quiver, or fibrillate. The quivering upsets the normal rhythm between the atria and the lower parts (ventricles) of the heart. The lower parts may beat fast and without a regular rhythm.

Atrial fibrillation is dangerous because it greatly increases the risk of stroke. If the heart doesn't beat strongly, blood can collect, or pool, in the atria. Pooled blood is more likely to form clots. If the heart pumps a clot into the bloodstream, the clot can travel to the brain and block blood flow, causing a stroke. Atrial fibrillation can also lead to heart failure or heart attack.

What causes atrial fibrillation?

Conditions that damage or strain the heart commonly cause atrial fibrillation. These include:

• High blood pressure.
• Coronary artery disease (CAD).
• Heart attack.
• Heart valve disease, especially diseases of the mitral valve.

Atrial fibrillation may also be caused by:

• Other medical problems, such as lung disease, pneumonia, or a high thyroid level (hyperthyroidism).
• Heart surgery.
• Heavy alcohol use. Having more than 3 drinks a day over many years can cause long-lasting atrial fibrillation. Drinking a large amount of alcohol at one time (binge drinking) may also cause a spell (episode) of atrial fibrillation.
• Use of stimulants. These include caffeine, nicotine, medicines such as decongestants, and illegal drugs such as cocaine.

Sometimes doctors can't find the cause. Doctors call this lone atrial fibrillation.

What are the symptoms?

Symptoms may include:

• Feeling dizzy or lightheaded.
• Feeling out of breath.
• Feeling weak and tired.
• A feeling that the heart is fluttering, racing, or pounding (palpitations).
• A feeling that the heart is beating unevenly.
• Chest pain (angina).
• Fainting.

Atrial fibrillation is common, especially in older adults, and it may not cause obvious symptoms. If you have any of the symptoms listed, see your doctor. Finding and treating atrial fibrillation right away can help you avoid serious problems.

How is atrial fibrillation diagnosed?

The doctor will ask questions about your past health, do a physical exam, and order tests. The best way to find out if you have atrial fibrillation is to have an electrocardiogram (EKG or ECG). An EKG is a test that checks for problems with the heart’s electrical activity.

You might also have lab tests, a chest X-ray, and an echocardiogram. An echocardiogram can show how well your heart is pumping and whether your heart valves are damaged.

How is it treated?

A number of treatments may be used for atrial fibrillation. Which treatments are best for you depend on the cause, your symptoms, and your risk of stroke.