Atrial fibrillation, also known as A-fib, is a relatively common condition in which the upper chambers of the heart (known as the atria) beat irregularly, or "fibrillate." That causes the
heart's overall beat to become irregular, and sometimes to beat very fast.
Many people don't notice any symptoms when that happens. Others develop noticeable symptoms, which may include a racing heartbeat, dizziness, and shortness of breath, among others.
Atrial fibrillation can be triggered by underlying damage to the heart muscle or by other illnesses, such as thyroid problems or even pneumonia. In some people it occurs intermittently (this is often called "paroxysmal" atrial fibrillation), but in many it becomes a chronic and constant heart rhythm.
The risk of having atrial fibrillation goes up with age and ranges from 0.5-1 percent among those ages 55-60 to 15-20 percent in those ages 80 or older.
In 2009, experts estimated that about 3 million Americans have atrial fibrillation.
People with atrial fibrillation need regular medical care to help their heart maintain its ability to effectively pump blood to the body. Atrial fibrillation also causes a significantly increased risk of stroke, so many people with atrial fibrillation end up taking blood thinners.