Atrial Fibrillation is the most common heart rythmn abnormatlity and is very common as you age. Atrial fibrillation is a condition in which the top chambers of the heart, the Atrium are fibrillating, rather than having a regular synchronized contraction. One of the worst complications of Atrial Fibrillation can be Stroke. There are very good treatments of Atrial Fibrillation. This animated video is an overview of Atrial Fibrillation.