The string phenomenon: an important cause of internal mammary artery graft failure.

Internal mammary arteries are the grafts of choice for coronary artery bypass because they are generally free of atherosclerosis and they have high patency rates as grafts. There are, however, increasing reports of graft failure due to diffuse or distal narrowing, known as the string phenomenon. From June 1999 to October 1999, we prospectively reviewed all cases of internal mammary artery angiography at our institution. Twenty-eight cases of internal mammary artery graft failure were identified (M:F, 15:13; mean age, 62 years) out of 261 patients who had undergone internal mammary artery grafting at any institution, including ours. The mean interval between coronary artery bypass and re-angiography was 35 months. There was evidence of competitive flow in 81% (22 of 27) of patients whose internal mammary grafts had developed the string sign. This observational study supports the hypothesis that competitive flow predisposes internal mammary grafts to the string phenomenon. Given the high frequency of competitive flow situations amongst patients with internal mammary artery graft failure, caution should be exercised in the anastomosis of the internal mammary artery to recipient vessels that are less than severely stenosed.