What about alternatives to oral anticoagulation?  Aspirin is commonly given to patients who are at risk of stroke but who are thought to have too high a risk of bleeding.  The Figure looks at 3 groups of patients with AFib and at risk for stroke, treated with warfarin vs no therapy (1st column),[69] aspirin vs no therapy (2nd column),[70] and warfarin vs aspirin (3rd column).[71]  In the first column, the relative risk reduction for stroke with warfarin vs no therapy is 68%,[69] whereas the relative risk reduction with aspirin vs no therapy is a far more modest 21%.[70]  Finally, comparing warfarin vs. aspirin, warfarin provided a 52% greater risk reduction than aspirin.[71]  In sum, antiplatelet therapy with aspirin does provide modest risk reduction compared with placebo (no therapy), but aspirin is clearly inferior to warfarin.  

Rothman SA. Am J Med 2013; 126: 00-00.