There was no evidence of a differential effect of apixaban over warfarin in patients with and without valvular heart disease in reducing stroke and systemic embolism ( hazard ratio [ HR ] , 0.70 ; 95 % confidence interval [ CI ] , 0.51-0 .97 and HR , 0.84 ; 95 % , CI 0.67-1 .04 ; interaction P = 0.38 ) , causing less major bleeding ( HR , 0.79 ; 95 % CI , 0.61-1 .04 and HR , 0.65 ; 95 % CI , 0.55-0 .77 ; interaction P = 0.23 ) , and reducing mortality ( HR , 1.01 ; 95 % CI , 0.84-1 .22 and HR , 0.84 ; 95 % CI , 0.73-0 .96 ; interaction P = 0.10 ) .