Biochemical composition of human internal mammary artery and saphenous vein

The long-term patency of the internal mammary artery graft is better than that of the saphenous vein graft in coronary bypass surgery because of a low incidence of atherosclerosis in the internal mammary artery. In search of a possible biochemical explanation of the low degree of atherosclerosis in the internal mammary artery we compared the chemical compositions of human internal mammary artery and saphenous vein obtained from 37 patients undergoing coronary bypass surgery. The levels of esterified cholesterol and free cholesterol were higher in the internal mammary artery than in the saphenous vein (p less than 0.001 and p less than 0.01, respectively), but lower than the levels reported in previous studies for coronary arteries. The amount of collagen was higher in the saphenous vein (p less than 0.001). Heparan sulfate was the major glycosaminoglycan fraction in the internal mammary artery, probably reflecting the higher cellularity and thicker media in the arterial rather than in the venous tissue. The level of dermatan sulfate was higher (p less than 0.001) in the saphenous vein than in the internal mammary artery. This difference is in a direction that could favor atherogenesis in the saphenous vein graft.