In patients who did not receive prestudy heparin , the incidences of recurrent VTE were similar in rivaroxaban ( 15 of 649 , 2.3 % ) and enoxaparin/VKA ( 13 of 695 , 1.9 % ) patients ( adjusted hazard ratio [ HR ] = 1.11 ; 95 % confidence interval [ CI ] = 0.52 to 2.37 ) .