Conclusions: Oral anticoagulation is the optimal choice of antithrombotic therapy for patients with AF at high risk of stroke (CHADS2 score of 2). At lower levels of stroke risk, antithrombotic treatment decisions will require a more individualized approach. Abbreviations: AAD5antiarrythmic drug; ACS5acute coronary syndrome; ACTIVE5Atrial Fibrillation Clopidogrel Trial With Irbesartan for Prevention of Vascular Events; AF5atrial brillation; AFASAK5Atrial Fibrillation Aspirin and Anticoagulation; AFFIRM5Atrial Fibrillation Follow-up Investigation of Rhythm Management; CHADS2 5congestive heart failure, hypertension, age 75 years, diabetes mellitus, prior stroke or transient ischemic attack; CHA2DS2- VASc5congestive heart failure (or left ventricular systolic dysfunction), hypertension, age 75 years, diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65 to 74 years, female sex; EAFT 5 European Atrial Fibrillation Trial; ESPS5European Stroke Prevention Study; INR5international normalized ratio; LAA5left atrial appendage; MI 5 myocardial infarction; PAF 5 paroxysmal atrial brillation; RCT 5 randomized controlled trial; RE-LY5Randomized Evaluation of Long-Term Anticoagulation Therapy; SPAF5Stroke Prevention in Atrial Fibrilla- tion; TEE5transesophageal echocardiography; TIA5transient ischemic attack; VKA5vitamin K antagonist Antithrombotic Therapy for Atrial Fibrillation Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines John J. You, MD; Daniel E. Singer, MD; Patricia A. Howard, PharmD; Deirdre A. Lane, PhD; Mark H. Eckman, MD; Margaret C. Fang, MD, MPH; Elaine M. Hylek, MD, MPH; Sam Schulman, MD, PhD; Alan S. Go, MD; Michael Hughes, PhD; Frederick A. Spencer, MD; Warren J. Manning, MD; Jonathan L. Halperin, MD; and Gregory Y. H. Lip, MD e532S Antithrombotic Therapy for Atrial Fibrillation oral anticoagulation (Grade 2B) or combination therapy with aspirin and clopidogrel (Grade 2B). 