DIFFERENCES IN VASOMOTOR CONTROL BETWEEN HUMAN GASTROEPIPLOIC AND LEFT INTERNAL MAMMARY ARTERY

Background. Internal mammary artery grafts have a greater long-term patency rate than do saphenous vein grafts. This has in part been attributed to the difference in endothelial function of arterial and venous vessels. The use of the gastroepiploic artery in coronary artery bypass grafting has become popular recently because of its similarity to internal mammary artery. In this study, we compared the endothelial responses of gastroepiploic and left internal mammary arteries to vasoactive substances.

Methods and Results. Gastroepiploic and left internal mammary arteries were obtained during surgery from patients undergoing elective coronary artery bypass surgery. Vascular rings of both graft types were studied in organ bath experiments. Relaxation responses to metacholine and sodium nitrite were similar in rings of both arteries. In contrast, bradykinin induced potent relaxations in rings of the gastroepiploic artery but not in rings of the left internal mammary artery. Furthermore, there was a inverse correlation of maximal metacholine-induced relaxations with increasing age.

Conclusions. The resemblance of relaxations induced by metacholine and sodium nitrite in both gastroepiploic and left internal mammary arteries suggests a similar activation and behavior of the L-arginine pathway in both arteries. The difference in bradykinin-induced relaxations may reflect a prostaglandin metabolism in the gastroepiploic artery different from that in the left internal mammary artery. Furthermore, maximal metacholine-induced relaxation in rings of the left internal mammary artery shows an age dependency that was not observed in rings of the gastroepiploic artery.