Atrial fibrillation (AF) or flutter is a common type of abnormal heartbeat. AF is the most common heart rhythm disturbance in the United States.  When AF occurs, the upper chambers of the heart (atria) quiver rapidly and irregularly (fibrillate).  AF can cause a range of symptoms from lack of energy, heart palpitations, chest pain and dizziness.  The cause of AF is unclear and potential causes are under investigation.  Dr. Sinjin Lee, MD takes a deeper look into atrial fibrillation, who is affected, the risks, treatment options and prevention.