Anticoagulation for Stroke Prevention in Atrial Fibrillation

Inclusion Criteria: 1. have ≥1 episode of clinically important AFOTS during any of the following conditions: 1. noncardiac surgery in the past 35 days, with at least an overnight hospital admission aftersurgery; 2. noncardiac day surgery resulting in a large enough physiological insult to be able to cause AFOTS, as judged by the local investigator; or 3. acute medical illness requiring hospital admission in the past 35 days and resulting in a large enough physiological insult to be able to cause AFOTS, as judged by the local investigator; 2. sinus rhythm at the time of randomization; 3. any of the following high-risk criteria: 1. age 55-64 years, and having either known cardiovascular disease, recent major vascular surgery, a CHA2DS2VASc score ≥3, or an elevated postoperative troponin level; 2. age 65-74 years, and having either known cardiovascular disease, recent major vascular surgery, a CHA2DS2VASc score ≥2, or an elevated postoperative troponin level; OR 3. age ≥75 years.; 4. provide written informed consent Exclusion Criteria: 1. any cardiac diagnosis as the primary reason for hospital admission; 2. history of documented chronic AF prior to noncardiac surgery; 3. need for long-term systemic anticoagulation; 4. ongoing need for long-term dual antiplatelet treatment; 5. contraindication to oral anticoagulation; 6. severe renal insufficiency (CrCl \<20 ml/min); 7. severe liver cirrhosis (i.e., Child-Pugh Class C) 8. acute stroke in the past 14 days; 9. underwent cardiac surgery in the past 35 days; 10. history of nontraumatic intracranial, intraocular, or spinal bleeding; 11. hemorrhagic disorder or bleeding diathesis; 12. expected to be non-compliant with follow-up and/or study medications; 13. known life expectancy less than 1 year due to concomitant disease; 14. women who are pregnant, breastfeeding, or of childbearing potential who are not taking effective contraception; OR 15. previously enrolled in the trial