Atrial fibrillation is the most common type of arrhythmia, which is an irregular heart rate or rhythm. If you have atrial fibrillation, your heart's electrical signals become rapid and disorganized, causing the two upper chambers of your heart (the atria) to contract quickly and irregularly. This abnormal rhythm is called fibrillation.

Your heart’s rate and rhythm are controlled by electrical signals that start in an area in the right atrium called the sinoatrial node (SA node). The SA node normally sends signals that cause the atria to contract and pump blood to the lower chambers of your heart (ventricles) at about 60 to 100 times per minute. With atrial fibrillation, the signals start outside the SA node and result in fibrillation.

Atrial fibrillation is caused by damage to your heart’s electrical system. Two common causes of this are high blood pressure and coronary artery disease, which is narrowing of the arteries that supply blood to your heart muscles. Sometimes, though, the cause isn't known. When the atria fibrillate, they don’t pump all of the blood out and into the ventricles. In addition, the atria and ventricles do not beat in a coordinated way. As a result, the amount of blood pumped out of the ventricles to the body is inconsistent. It may be rapid small amounts of blood or sporadic large amounts of blood.

There are different types of atrial fibrillation. It may be temporary, starting suddenly and then stopping on its own, usually within 24 hours. That's paroxysmal atrial fibrillation. Or, it may be ongoing. Persistent atrial fibrillation starts suddenly and continues for more than a week, sometimes stopping on its own and other times requiring medication or other treatment to restore a normal heart rhythm. Permanent atrial fibrillation is always present. It does not stop on its own or with treatment.

Possible complications of atrial fibrillation include stroke and heart failure. Atrial fibrillation causes blood to pool in your atria, which can cause a blood clot to form. If a clot breaks free and blocks blood flow to your brain, you could have a stroke. Atrial fibrillation also makes your heart work harder to pump blood out to your body. Over time, fluid can back up into your lungs and can start to pool in your legs. These are signs of heart weakening called heart failure.

Though these complications are possible, most people with atrial fibrillation can lead normal, active lives. You may need treatment, however, to restore a normal heart rhythm and prevent stroke. Treatments could include medications, medical procedures and lifestyle changes.

Symptoms of Atrial Fibrillation

The following symptoms of atrial fibrillation are the most common. However, many people have no symptoms at all. With or without symptoms, atrial fibrillation increases the risk of having a stroke or heart failure.

  • Lack of energy and fatigue (the most common symptoms)
  • Irregular or rapid heartbeat or pulse
  • Heart palpitations (feeling skipped beats, rapid beats or fluttering)
  • Lightheadedness or fainting
  • Confusion
  • Shortness of breath
  • Chest pain
  • Weakness or shortness of breath when exercising
  • Frequent urination

Risk Factors for Atrial Fibrillation

More than 3 million Americans have atrial fibrillation. The condition is more common among white men. Other risk factors include:

  • High blood pressure
  • Heart failure
  • Coronary artery disease
  • Diabetes
  • Advanced age (older than 60)
  • Overactive thyroid (hyperthyroidism)
  • Heart valve disease
  • Heart defects from birth (congenital heart disease)
  • Pericarditis (inflamed tissues around the heart)
  • Heart attack or heart surgery
  • Abuse of alcohol
  • Obesity
  • Lung disease
  • Interrupted breathing at night (sleep apnea)
  • Family history of atrial fibrillation