Atrial fibrillation is the most common serious rhythm disorder seen by adult cardiologists. The incidence of atrial fibrillation is increasing throughout the United States. As the population ages, it is expected that even a greater number of patients will require care for this arrhythmia. Atrial fibrillation occurs when the upper chambers of the heart (atria) become controlled by a chaotic series of electrical impulses. This can lead to a very rapid and irregular heartbeat. Even more seriously, atrial fibrillation significantly increases a person’s risk of stroke. The cardiologist helps identify the cause of atrial fibrillation and can determine the optimal approach to managing the fibrillation. Also, the cardiologist can determine how best to prevent stroke in the setting of underlying atrial fibrillation.