Health A-to-Z: Atrial Fibrillation


What Is It?


Atrial fibrillation is a heart rhythm disorder that causes a rapid and irregular heartbeat.

The atria are the upper two chambers of the heart that receive blood from the rest of the body. They pump blood into the lower two chambers (the ventricles). Then the ventricles pump blood to the rest of the body. During atrial fibrillation, the atria do not beat normally. Instead, they quiver or “fibrillate.”

Normally, electrical impulses from a small part of the atrium called the sinus node cause the atria to beat. The electrical signal then goes through another part of the heart called the atrioventricular node. Then it goes down to the ventricles, and causes them to beat. First the atria, then the ventricles: it is coordinated, and so the heart pumps blood efficiently. The atria pump, filling the ventricles with blood, and then the ventricles pump.

In contrast, during atrial fibrillation, the electrical impulses come from all over the atria. Instead of pumping efficiently, the atria just quiver. There is an irregular and rapid heartbeat. There is no coordination between the atria and the ventricles. As a result, the atria do not pump all of their blood into the ventricles. Also, the ventricles sometimes pump when they don’t have a lot of blood in them.

A normal heartbeat is 60 to 100 beats per minute, and very regular: beat…beat…beat…beat. During atrial fibrillation, the heart beats at 80 to 160 beats per minute, and is very irregular: beat..beat…..beat….beat.beat.beat….beat.

Atrial fibrillation can lead to the formation of blood clots inside the atria. This is a serious, longer-term problem. These blood clots can travel out of the heart and get stuck in an artery to the lungs (causing a pulmonary embolism), an artery to the brain (causing a stroke) or an artery elsewhere in the body.When the hearts beats rapidly and irregularly, it cannot pump blood out of the heart efficiently. As a result, some people get short of breath. Some people faint.




The major factors that increase the risk of atrial fibrillation are:

  • Age
  • Coronary artery disease
  • Rheumatic heart disease
  • High blood pressure
  • Diabetes
  • An excess of thyroid hormones

In many people, the cause of atrial fibrillation is more serious than the fibrillation itself.


Atrial fibrillation often doesn’t cause any symptoms. When symptoms occur, they can include:

  • Palpitations (awareness of a rapid heartbeat)
  • Fainting
  • Dizziness
  • Weakness
  • Shortness of breath
  • Chest pain

Some people with atrial fibrillation have periods of normal heartbeats: the atrial fibrillation comes and goes. In many others, the atrial fibrillation remains for the rest of their lives.

Risk Factors


Your doctor will ask about your family history of cardiovascular disorders. He or she will review your personal medical history. This includes any possible risk factors for atrial fibrillation.

Your doctor will ask about your specific heart symptoms, including possible triggers for your symptoms.

Your doctor will examine you. He or she will check your heart rate and rhythm and your pulse. In atrial fibrillation, your pulse often doesn’t match your heart sounds.

The diagnosis of atrial fibrillation is usually confirmed with an electrocardiogram (EKG). An EKG is a test that records the heart’s electrical activity. However, because atrial fibrillation can come and go, a standard EKG may be normal.

If this is the case, an ambulatory EKG may be done. During this test, the patient wears a portable EKG machine (Holter monitor). The Holter monitor is usually worn for 24 hours.

If your symptoms appear less frequently than once a day, your doctor may use an event recorder. You keep an event recorder with you for several days or even weeks. It attempts to capture your heart rhythm at the time you feel an irregular beat.


Expected Duration

How long the condition lasts depends on the cause. Atrial fibrillation caused by a treatable condition may go away when the condition is treated.

However, atrial fibrillation is often a lifelong condition. This is more likely when it has no known cause or results from a long-standing cardiac disorder.


Atrial fibrillation resulting from coronary artery disease can be prevented. Take these actions to reduce your risk:

  • Eat a low-fat diet.
  • Control cholesterol and high blood pressure.
  • Do not drink more than two alcoholic drinks per day.
  • Quit smoking.
  • Control your weight.
  • Get regular exercise.

Some causes of atrial fibrillation cannot be prevented.


Treatment depends on the cause.

If the cause is coronary artery disease, treatment may consist of:

  • Lifestyle changes
  • Cholesterol-lowering medications
  • Blood pressure medications
  • Angioplasty
  • Coronary artery bypass surgery

Atrial fibrillation caused by an excess of thyroid hormones can be treated with medication or surgery. When rheumatic heart disease is the cause, the condition may be treated with surgery to replace heart valves damaged by the disease.

The irregular heartbeat can be treated with medications. These include beta blockers, calcium-channel blockers, and digoxin.

In addition, people with atrial fibrillation often are given blood thinning medications. These drugs prevent blood clots.

Antiarrhythmic drugs may be given to try to prevent atrial fibrillation from returning.

Another treatment option is electrical cardioversion. This procedure works in most cases. But more than half of patients eventually develop atrial fibrillation again.

Evidence suggests that conversion of patients from atrial fibrillation back into a normal rhythm does not prolong life.

If patients have symptoms even with medications to control heart rate, then cardioversion is still worth trying. But for patients who are not having symptoms from it, a reasonable approach is to simply live with the condition. In that case, doctors almost always prescribe treatment with blood thinners. This will help to prevent blood clots.

Sometimes medications cannot control a patient’s symptoms or heart rate. In this case, a procedure called catheter radiofrequency ablation might be an option. In this procedure, the areas of the atrium and nearby structures that are causing the irregular electrical activity are destroyed.

Another surgical procedure involves creating scars in the atria. This hinders abnormal electrical activity from spreading and causing atrial fibrillation.

When To Call A Professional

Call your doctor if you have any of the symptoms of atrial fibrillation. This includes:

  • Palpitations
  • Faintness
  • Dizziness
  • Weakness
  • Shortness of breath
  • Chest pain


When a cause of atrial fibrillation is identified and treated, the arrhythmia often goes away. It is less likely to go away in people who have long-standing rheumatic heart disease or any condition in which the atria are enlarged.

Blood thinning medications can reduce the risk of a stroke or other complications.

Additional Info

American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231
Toll-Free: 1-800-242-8721

National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105
Phone: 301-592-8573
TTY: 240-629-3255
Fax: 301-592-8563

American College of Cardiology
Heart House
9111 Old Georgetown Road
Bethesda, MD 20814-1699
Phone: 301-897-5400
Toll-Free: 1-800-253-4636, ext. 694
Fax: -301-897-9745



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