After multivariable adjustment , longer surgical duration ( odds ratio per 10-minute increase , 1.05 ; 95 % confidence interval , 1.03-1 .07 ) , endoscopic vein harvesting ( odds ratio , 1.41 ; 95 % confidence interval , 1.16-1 .71 ) , poor target artery quality ( odds ratio , 1.43 ; 95 % confidence interval , 1.11-1 .84 ) , and postoperative use of clopidogrel or ticlopidine ( odds ratio , 1.35 ; 95 % confidence interval , 1.07-1 .69 ) were associated with patient-level VGF .