A COMPARISON OF INTERNAL MAMMARY ARTERY AND SAPHENOUS-VEIN GRAFTS AFTER CORONARY-ARTERY BYPASS-SURGERY - NO DIFFERENCE IN 1-YEAR OCCLUSION RATES AND CLINICAL OUTCOME

Background Superior patency rates for internal mammary artery (IMA) gr afts compared with vein coronary bypass grafts have been demonstrated by retrospective studies. This difference may have been affected by se lection bias of patients and coronary arteries for IMA grafting. Metho ds and Results To estimate the difference between IMA and vein grafts, we analyzed graft patency data of 912 patients who entered a randomiz ed clinical drug trial. In this trial, 494 patients received both IMA and vein grafts (group 1) and 418 only vein grafts (group 2). Occlusio n rates of IMA grafts and IMA plus vein grafts in group 1 were compare d with those of vein grafts in group 2. Multivariate analysis was used to compare occlusion rates of IMA and vein grafts while other variabl es related to graft patency were controlled for. In addition, 1-year c linical outcome was assessed by the incidence of myocardial infarction , thrombosis, major bleeding, and death. Occlusion rates of distal ana stomoses in group 1 versus group 2 were 5.4% (IMA grafts) versus 12.7% (vein grafts) (P<.0001) and 10.4% (IMA plus vein grafts) versus 12.7% (vein grafts) (P=.14). There was no difference in adjusted risk of oc clusion between IMA grafts and vein grafts (P=.089). Type and location of distal anastomosis and lumen diameter of the grafted coronary arte ry were shown to be predictors of occlusion. Clinical events occurred in 17.8% (group 1) and 16.0% (group 2) of patients (P=.53). Conclusion s The observed difference in 1-year occlusion rates between IMA and ve in grafts can be explained by a maldistribution of graft characteristi cs by selection of coronary arteries for IMA grafting rather than bein g ascribed to graft material. One-year clinical outcome is not improve d by IMA grafting.