The purpose of this research is to learn more about the normal care of patients with a new or pre-existing diagnosis of atrial fibrillation (AF). These abnormal and irregular heartbeats place patients at increased risk of developing clots in their bloodstream that could potentially lead to stroke. Normal care is designed to help prevent this from happening and to lessen or eliminate the symptoms patients may have. There are many different types of AF as well as numerous ways in which a variety of patients are treated. The investigators are interested in gathering more information to better keep track of patient treatment patterns (trends) that may differ from physician to physician, hospital to hospital, medication to medication, patient to patient and if necessary, procedure to procedure.