More than 2 million Americans have the abnormal heart rhythm known as atrial fibrillation. This abnormal rhythm usually causes palpitations, and can also cause shortness of breath, chest pain and poor exercise tolerance. Occasionally, patients with atrial fibrillation have no symptoms and are unaware of the abnormal rhythm. The top chambers of the heart, called the atria, act as a receiving chamber, and do not normally pump a significant amount of blood. They keep the pace for the heart and tell it when to beat.
Atrial fibrillation occurs when the atria stop beating rhythmically and begin to quiver.
This chaotic quivering causes the heart to lose its primary source of timing. Usually, it begins to beat very rapidly, though it can occasionally beat too slowly or at a normal pace. During atrial fibrillation, the heart almost always beats irregularly. Many things can cause atrial fibrillation. Blockages in the arteries of the heart can deprive parts of the heart of blood and can lead to atrial fibrillation.