Cardiac Conditions & Diseases

Our Services Education

What Is Atrial Fibrillation?

Atrial fibrillation (A-tre-al fi-bri-LA-shun), or AF, is the most common type of arrhythmia (ah-RITH-me-ah). An arrhythmia is a problem with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.

AF occurs when rapid, disorganized electrical signals cause the atria (AY-tree-uh), the two upper chambers of the heart, to fibrillate. The term "fibrillate" means to contract very fast and irregularly.

In AF, blood pools in the atria and isn't pumped completely into the ventricles (VEN-trih-kuls), the heart's two lower chambers. As a result, the heart's upper and lower chambers don't work together as they should.

Often, people who have AF may not feel symptoms. However, even when not noticed, AF can increase the risk of stroke. In some people, AF can cause chest pain or heart failure, particularly when the heart rhythm is very rapid.

AF may occur rarely or every now and then, or it may become a persistent or permanent heart rhythm lasting for years

What Causes Atrial Fibrillation?

Atrial fibrillation (AF) occurs when the electrical signals traveling through the heart are conducted abnormally and become very rapid and disorganized.

This is the result of damage to the heart's electrical system. The damage most often is the result of other conditions, such as coronary heart disease (also called coronary artery disease) or high blood pressure, that affect the health of the heart.

Sometimes, the cause of AF is unknown.

Who Is At Risk for Atrial Fibrillation?

More than 2 million people in the United States have atrial fibrillation (AF). It affects both men and women.

The risk of AF increases as you age. This is mostly because as you get older, your risk for heart disease and other conditions that can cause AF also increases. However, about half of the people who have AF are younger than 75.

AF is uncommon in children.

Major Risk Factors

AF is more common in people who have heart diseases or conditions, such as:

  • Coronary heart disease
  • Heart failure
  • Rheumatic heart disease
  • Structural heart defects, such as mitral valve disorders
  • Pericarditis (a condition in which the membrane, or sac, around your heart is inflamed)
  • Congenital heart defects
  • Sick sinus syndrome (a condition in which the heart's electrical signals don't fire properly and the heart rate slows down; sometimes the heart will switch back and forth between a slow rate and a fast rate)

AF also is more common in people who are having heart attacks or who have just had surgery.

What Are the Signs and Symptoms of Atrial Fibrillation?

Atrial fibrillation (AF) usually causes the ventricles to contract faster than normal. When this happens, the ventricles don't have enough time to fill completely with blood to pump to the lungs and body.

This inefficient pumping can cause signs and symptoms, such as:

  • Palpitations (feelings that your heart is skipping a beat, fluttering, or beating too hard or fast)
  • Shortness of breath
  • Weakness or difficulty exercising
  • Chest pain
  • Dizziness or fainting
  • Fatigue (tiredness)
  • Confusion

Information provided by National Heart Lung and Blood Institute