Speci cally, for literature regarding the assess- ment of stroke risk in patients with AF, we searched Medline for articles published from January 1, 2005, to October 2009 using the search terms atrial brillation, atrial utter, risk assess- ment, risk factors, risk strati cation, stroke, and thrombo- embolism. For literature regarding prevention of stroke and thromboembolism in patients with AF, we searched Medline for articles published from January 1, 2005, to October 2009 using the search terms coumarins, warfarin, dicumarol, phenprocoumon, acenocoumarol, fondaparinux, idraparinux, aspirin, tri usal, indobufen, dabigatran, ximelagatran, rivaroxaban, apixaban, ticlopidine, clopidogrel, catheter ablation, watchman, PLAATO, cardioversion, atrial bril- lation, and atrial utter. 1.1 Outcomes of Interest The outcomes most relevant to patients with AF include death, nonfatal stroke, systemic embolism, nonfatal major extracranial bleeding, and the burden and lifestyle limitations associated with outpatient antithrombotic therapy. To facilitate decision-making, the term stroke in this article includes ischemic stroke and intra- cranial hemorrhage (intracerebral, subdural, and subarachnoid hemorrhage). Although there may be some differences in the impact of these intracranial events (eg, subdural hemorrhage) on quality of life, we judged that on average, the impact would be similar. We also explicitly considered that outpatient antithrom- botic therapy was associated with a burden to the patient, which in some cases, such as aspirin, is a requirement to take a daily medication, or in other cases, such as adjusted-dose VKA therapy, is not only a requirement to take a daily medication but also a requirement to limit one s lifestyle, restrict one s diet, and undergo e536S Antithrombotic Therapy for Atrial Fibrillation Table [Introduction] Clinical Questions Addressed in This Article Section Population Intervention Comparator Outcomes of Interest Available Methodology 2. 