Among patients undergoing open and closed tunnel EVH , no difference in the per-patient incidence of vein graft failure ( 43.8 % vs 47.1 % ; adjusted odds ratio , 0.91 ; 95 % confidence interval , 0.53-1 .55 ; P = 0.724 ) or per-graft incidence of vein graft failure ( 25.5 % vs 25.9 % ; adjusted odds ratio , 0.96 ; 95 % confidence interval , 0.59-1 .55 ; P = 0.847 ) was observed .