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 ( @ per @ patient-years vs. @ per @ patient-years ; adjusted hazard ratio -LSB- HR -RSB- : @ ; @ % confidence interval -LSB- CI -RSB- : @ to @ ) or aspirin plus clopidogrel ( @ vs. @ ; adjusted HR : @ ; @ % CI : @ to @ ; p ( interaction ) = @ ) .