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Atrial Fibrillation Health Center

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    What is atrial fibrillation?

    Atrial fibrillation (say "AY-tree-uhl fih-bruh-LAY-shun") is the most common type of irregular heartbeat (arrhythmia).

    Normally, the heart beats in a strong, steady rhythm. In atrial fibrillation, a problem with the heart's electrical system causes the two upper parts of the heart, the atria, to quiver, or fibrillate.

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    The quivering upsets the normal rhythm between the atria and the lower parts of the heart, the ventricles. And the ventricles may beat fast and without a regular rhythm.

    This is dangerous because if the heartbeat isn't strong and steady, blood can collect, or pool, in the atria. And pooled blood is more likely to form clots. Clots can travel to the brain, block blood flow, and cause a stroke.

    Interactive Tool: What Is Your Risk for a Stroke if You Have Atrial Fibrillation?

    Atrial fibrillation can also lead to heart failure.

    What causes atrial fibrillation?

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

    Other possible causes include:

    • Other medical problems, such as heart failure, lung disease, pneumonia, or a high thyroid level.
    • Heart surgery.
    • Heavy alcohol use. This includes having more than 3 drinks a day over many years as well as drinking a large amount of alcohol at one time (binge drinking).
    • Use of stimulants. These include nicotine, medicines such as decongestants, and illegal drugs such as cocaine.
    • Use of some prescription medicines, such as albuterol or theophylline.

    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.
    • Feeling like the heart is fluttering, racing, or pounding (palpitations).
    • Feeling like the heart is beating unevenly.
    • Having chest pain (angina).
    • Fainting.

    Sometimes atrial fibrillation doesn't cause obvious symptoms.

    If you have symptoms, see your doctor. Finding and treating atrial fibrillation right away can help you avoid serious problems.

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