Indications for the internal mammary artery graft

Experience of 285 internal mammary artery (IMA) grafts inserted during a five-year period disclosed an operative mortality of 1.5% when patients with associated procedures were excluded. Two of nine patients undergoing concomitant intracardiac surgery died within one month. Thus the overall operative mortality was 2.1%. Preoperative IMA graft blood flow was significantly less than that through comparable aortocoronary saphenous vein grafts. Early IMA graft patency (two weeks) was 95% and the cumulative late patency (one year) was 91%. Early patency for IMA grafts with peroperative flow less than 20 ml was 70%. None of these grafts were occluded at late follow-up. Sixteen occluded IMA grafts were related to technical problems (six grafts), inadequate graft size (five), extensive disease of the recipient coronary artery (four) and to overestimated proximal stenosis with large competitive flow enhancing early graft failure (one graft). Retrograde filing of the IMA when contrast was injected into the recipient coronary artery, was observed in 7 patients (3%). Probable causes were proximal stenosis of the graft, small sized IMA with inadequate antegrade flow and overestimated proximal coronary obstruction. Prerequisites for performing optimal IMA grafting need pre- and peroperative caution. A good calibre IMA without proximal obstructions must be available. The technique of dissecting and handling the vessel and performing anastomosis must be careful. The recipient coronary artery should be selected with consideration in order to avoid unfavourable demand-supply ratios. The IMA is most suitable for low-flow situations supplying a small amount fo myocardium distal to a high-grade coronary obstruction.