Atrial fibrillation (AF) is an abnormal heartbeat that affects the upper chambers of the heart, or atria. The heart normally beats in a rhythmic, predictable pattern, between 60 and 100 times per minute. This beat is stimulated by an electrical signal that originates from within the heart. Any variation in this pattern, or abnormal heart beat, is known as an arrhythmia. Atrial fibrillation is the most common type of sustained arrhythmia. It affects about 2 million Americans every year.

During atrial fibrillation the atria quiver rather than contract normally because of rapid and irregular electrical signals in the heart. The result is an abnormally fast and/or irregular heartbeat as the chaotic signals travel to the ventricles, which are the heart’s main pumping chambers.

Beside the abnormal heartbeat, there is also a risk that blood will pool in the atria, possibly causing the formation of blood clots. If a blood clot breaks off into the general circulation, it may cause a stroke. Atrial fibrillation causes approximately 15 percent of all strokes. The risk of stroke can be reduced by taking anticoagulants (medications that inhibit blood clotting). Atrial fibrillation is also associated with greater complications and greater risk of death from heart attacks in people over the age of 65.

Many conditions may cause atrial fibrillation, including heart failure, high blood pressure or valvular heart disease. Many patients also experience atrial fibrillation in the absence of structural heart disease. If necessary, cardioversion may be used to bring the heartbeat back to normal by using either drugs or defibrillator paddles that deliver an electric shock to the patient’s chest. However, there is a risk that atrial fibrillation may happen again. Therefore, antiarrhythmic drugs may be required to maintain a normal rhythm. Surgery or ablation may also be options in some cases. With treatment, patients with AF are able to live normal, active lives. Some patients will also be prescribed anticoagulant medication to prevent the threat of future blood clots forming.