CHEST Supplement www.chestpubs.org CHEST / 141 / 2 / FEBRUARY, 2012 SUPPLEMENT e531S ANTITHROMBOTICTHERAPY AND PREVENTION OFTHROMBOSIS, 9TH ED: ACCP GUIDELINES Background: The risk of stroke varies considerably across different groups of patients with atrial brillation (AF). Antithrombotic prophylaxis for stroke is associated with an increased risk of bleeding. We provide recommendations for antithrombotic treatment based on net clinical ben- e t for patients with AF at varying levels of stroke risk and in a number of common clinical scenarios. Methods: We used the methods described in the Methodology for the Development of Antithrom- botic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Preven- tion of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines article of this supplement. Results: For patients with nonrheumatic AF, including those with paroxysmal AF, who are (1) at low risk of stroke (eg, CHADS2 [congestive heart failure, hypertension, age 75 years, diabetes mellitus, prior stroke or transient ischemic attack] score of 0), we suggest no therapy rather than antithrombotic therapy, and for patients choosing antithrombotic therapy, we suggest aspirin rather than oral anticoagulation or combination therapy with aspirin and clopidogrel; (2) at inter- mediate risk of stroke (eg, CHADS2 score of 1), we recommend oral anticoagulation rather than no therapy, and we suggest oral anticoagulation rather than aspirin or combination therapy with aspirin and clopidogrel; and (3) at high risk of stroke (eg, CHADS2 score of 2), we recommend oral anticoagulation rather than no therapy, aspirin, or combination therapy with aspirin and clopidogrel. Where we recommend or suggest in favor of oral anticoagulation, we suggest dabiga- tran 150 mg bid rather than adjusted-dose vitamin K antagonist therapy. Conclusions: Oral anticoagulation is the optimal choice of antithrombotic therapy for patients with AF at high risk of stroke (CHADS2 score of 2). 