No differential effect of apixaban versus placebo was observed for the composite endpoint of cardiovascular death , myocardial infarction , and ischemic stroke in patients taking aspirin ( 12.21 per 100 patient-years vs. 13.21 per 100 patient-years ; adjusted hazard ratio [ HR ] : 0.91 ; 95 % confidence interval [ CI ] : 0.62 to 1.32 ) or aspirin plus clopidogrel ( 13.22 vs. 14.24 ; adjusted HR : 0.95 ; 95 % CI : 0.78 to 1.14 ; p ( interaction ) = 0.84 ) .