Important Anatomical and Physiological Considerations in Performance of Complex Mammary–Coronary Artery Operations

Abstract

One or more internal mammary artery (IMA) anastomoses were performed in 87% of 692 consecutive coronary artery bypass operations performed over a 20-month period. One IMA was used in 68% (N = 469) and both IMAs were used in 19% (N = 130). Only saphenous vein grafts were used in 13% (N = 93). The mean number of anastomoses (all types) was 3.5. Fifty-seven patients were having a reoperation; bilateral IMA grafting was performed in 23% (N = 13). In 60 patients, 3 or more IMA anastomoses were performed: 3 IMA anastomoses, 50 patients; 4, 9 patients; and 5, 1 patient. In 27 patients, repeat coronary arteriography was performed within 30 days of operation to evaluate dynamics of IMA, saphenous vein, and native coronary artery flow. Major flow or all flow was through the graft (vs. the native coronary artery) in 62% of in situ IMA bypass grafts, 86% of free IMA grafts and 94% of saphenous vein grafts. Hospital mortality excluding patients having reoperation was 1.7% (11/635); it was less than 1% for patients having either single IMA grafting procedures (4/437) or bilateral IMA grafting procedures (1/117). Hospital mortality for patients receiving only saphenous vein grafts was surprisingly high, 7.4% (6/81). Major determinants of flow through the in situ IMA sequential graft are the size and flow of the IMA, the degree of proximal native coronary artery narrowing, the distally grafted to proximally grafted coronary artery size ratio, and probably the size of the side-to-side anastomosis. Technical factors important for multiple IMA grafts are the length and diameter of the IMA, use of the diamond anastomosis, absence of coronary artery disease at side-to-side anastomoses, epicardial location of the coronary artery, and no angulation distal to the sites of sequential anastomoses. Unless ideal conditions of IMA flow and size are met, an IMA graft supplying more than two coronary arteries might better be done with a free IMA graft.