Atrial Fibrillation


What Is It?

Atrial fibrillation is a type of cardiac arrhythmia (abnormality of heart rate or rhythm). Atrial fibrillation produces a rapid and irregular heartbeat, during which the atria (the upper two chambers of the heart that receive blood) quiver or “fibrillate” instead of beating normally.

During a normal heartbeat, the electrical impulses that cause the atria to contract come from the sinus node, a small area of the right atrium. During atrial fibrillation, however, these impulses come from all over the atria, triggering 300 to 500 contractions per minute within the heart’s upper chambers. Under normal circumstances, the atrioventricular node would receive these impulses and conduct them to the ventricles (the lower two chambers of the heart that do the pumping). During atrial fibrillation, however, the atrioventricular node becomes overwhelmed by all of the impulses it receives from the atria, and the result is an irregular and rapid heartbeat — 80 to 160 beats per minute versus a normal range of 60 to 100 beats per minute.

The rapid and irregular heartbeat produced by atrial fibrillation cannot pump blood out of the heart efficiently. As a result, blood tends to pool in the heart chambers, increasing the risk of a blood clot formaing inside the heart. Blood clots can travel from the heart into the bloodstream and circulate through the body. Ultimately, they may become lodged in an artery, causing Pulmonary embolism, stroke and other disorders.

In general, anything that disturbs the normal electrical impulses in the heart can trigger a cardiac arrhythmia, causing the heart to beat too quickly, too slowly or erratically. The major factors that increase the risk of atrial fibrillation are:

  • Age
  • coronary artery disease
  • Rheumatic heart disease (caused by rheumatic fever)
  • High blood pressure (hypertension)
  • diabetes
  • Thyrotoxicosis (an excess of thyroid hormones)

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


Atrial fibrillation often causes no symptoms at all. When symptoms do occur, there may be palpitations (awareness of a rapid heartbeat), fainting, dizziness, weakness, shortness of breath and angina pectoris (chest pain caused by a reduced blood supply to the heart muscle). Some people with atrial fibrillation have periods of completely normal heartbeats.


Your doctor will ask about your family history of cardiovascular disorders and will review your personal medical history, including any possible risk factors for atrial fibrillation. Your doctor also will ask you to describe your specific cardiac symptoms, including any possible triggers for your palpitations, dizziness or shortness of breath.

During your physical examination, the doctor will check your heart rate and rhythm, together with your pulses. In atrial fibrillation, the pulse, which reflects the activity of the ventricles, often is mismatched with the heart sounds, because all of the atrial beats are not reaching the ventricles.

The diagnosis of atrial fibrillation usually can be confirmed with an electrocardiogram (EKG). However, because atrial fibrillation tends to come and go, a regular EKG may be normal. If this is the case, ambulatory electrocardiography may be required. During ambulatory electrocardiography, the patient wears a portable EKG machine called a Holter monitor, usually for 24 hours.

Expected Duration

The duration of atrial fibrillation depends on the underlying cause. For example, if atrial fibrillation is caused by coronary heart disease, rheumatic heart disease, hypertension or thyrotoxicosis, the abnormal rhythm may resolve when the underling disorder is treated. However, atrial fibrillation that has no known cause, or that results from a long standing cardiac disorder, is often a lifelong condition.


Atrial fibrillation resulting from coronary artery disease can be prevented by taking these actions to modify your risk factors:

  • Eating a low fat diet
  • Controlling cholesterol and high blood pressure
  • Quitting smoking
  • Controlling your weight
  • Getting regular exercise

Some causes of atrial fibrillation cannot be prevented.


Treatment depends on the underlying cause. If the cause is coronary artery disease, treatment may consist of lifestyle changes, medications that treat high blood cholesterol and high blood pressure and/or procedures such as angioplasty and coronary artery bypass surgery. Atrial fibrillation resulting from thyrotoxicosis can be treated with medication or surgery, while fibrillation resulting from rheumatic heart disease may be treated by replacing damaged heart valves.

The arrhythmia of atrial fibrillation can be treated with medications, such as diltiazem hydrochloride (Cardizem), digoxin (Lanoxin) or verapamil (Tarka), which work to slow the heart rate. Another treatment option is electrical cardioversion, a procedure that delivers an Electrical shock to the heart to restore normal heart rhythm. Although this procedure is effective in most cases, between 50 percent and 75 percent of patients eventually develop atrial fibrillation again. Drugs such as amiodarone (Cordarone), procainamide (Procan SR, Promine, Pronestyl) or quinidine (Cardioquin, Quinaglute Dura-tabs, Quinidex Extentabs, Quin-Release) may be given to try to prevent relapses of atrial fibrillation.

When medications are ineffective, catheter radiofrequency ablation sometimes can be performed. In this procedure, an area of tissue in the atrioventricular node is destroyed to prevent the passage of excess electrical impulses from the atria to the ventricles. The result is often complete blockage of all electrical impulses. A pacemaker is then implanted to control the heart rate and rhythm.

In addition to the treatments described above, people with atrial fibrillation often are given medications to prevent blood clots that can lead to stroke, Pulmonary embolism and other complications. Treatment usually consists of anticoagulant medications (blood thinners), such as aspirin and warfarin (Coumadin).

When To Call A Professional

Call your doctor if you have any of the symptoms of atrial fibrillation, including palpitations, faintness, dizziness, weakness, shortness of breath or chest pain.


When an underlying cause of atrial fibrillation is identified and treated, the arrhythmia frequently goes away. Achieving a normal heartbeat is less likely for people who have long standing rheumatic heart disease or any condition in which the atria are enlarged.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.