Logistic multivariate analysis showed that preprocedure use of vitamin C is an independent predictor of PMI either defined by troponin I ( odds ratio [ OR ] , 0.56 ; 95 % confidence interval [ CI ] , 0.33-0 .97 ; P = 0.037 ) or by CK-MB ( OR , 0.37 ; 95 % CI , 0.14-0 .99 ; P = 0.048 ) .