Assumptions underlying these estimates are detailed in section of this article. f Restricting meta-analysis exclusively to RCTs evaluating aspirin alone vs no antithrombotic therapy (ie, excluding SAFT, which used aspirin in combination with xed minidose warfarin, and excluding the dipyridamole monotherapy arm of results in an estimate of relative risk that includes no effect (relative risk, CI, 0.66-1.01). g Of the nonfatal strokes on no therapy, an estimated were ischemic, and four were hemorrhagic. h Of the nonfatal strokes on antiplatelet therapy, an estimated were ischemic, and four were hemorrhagic. i We estimated the annual rates of nonfatal stroke (ischemic and hemorrhagic) on no therapy by extrapolating from observed annual rates of ischemic stroke (fatal nonfatal), strati ed by CHADS score, in the aspirin arms of six historical RCTs in patients with AF (Gage et al ). Assumptions underlying these estimates are detailed in section of this article. j We used evidence from RCTs of aspirin for the secondary prevention of cardiovascular events to obtain a best estimate of the risk of major extracranial bleeding with antiplatelet monotherapy. Note that the study event rates and relative risk are for the outcome of all major extracranial bleeding (nonfatal and fatal events) because speci c data regarding nonfatal events were not reported. k Rates of nonfatal major extracranial bleeding on no therapy are extrapolated from rates observed in observational cohorts of patients receiving adjusted-dose VKA therapy (median, and dividing by the relative risk of major bleeding on adjusted-dose VKA therapy observed in the RCTs. l The CI does not exclude the possibility of appreciable harm or bene t with antiplatelet therapy. 