Internal mammary artery bypass graft--long-term patency rate and follow-up

Between December, 1968, and January, 1974, 814 internal mammary artery and 351 saphenous vein bypass graft procedures were performed in 628 patients. Operative mortality during the past 3 years has been 1.7%. Internal mammary artery bypasses were performed to the anterior descending, circumflex, obtuse marginal, distal right, and posterior descending right coronary arteries. Ninety-one patients having 137 internal mammary artery and 32 saphenous vein grafts were studied angiographically 12 to 36 months postoperatively. All but 2 internal mammary artery bypasses were patent, a patency rate of 98.5%; 27 of the 32 saphenous vein bypasses in this group were patent (84.3%). The majority of the internal mammary artery bypasses were to distal coronary arteries, while the saphenous veins were used primarily for proximal anastomosis. Cineangiographic volume/flow studies were also performed. The average flow in the more distal internal mammary artery bypasses was 61 ml. per minute as compared with 91 ml. per minute in the proximal saphenous vein grafts.