The fate of internal mammary arterial implants and bypass conduits for myocardial revascularization. Experimental angiographic, histologic, and ultrastructural observations.

Experimental angiographic, histologic, and ultrastructural observations were obtained from dogs to determine the fate of internal mammary artery (IMA) implants and aorta-coronary bypass (ACB) conduits in the 3 month postoperative period. Angiographic implant patency and evidence of implants forming collaterals with the coronary circulation did not accurately reflect anatomic luminal narrowing. Subendothelial fibrocellular proliferation similar to that described in saphenous vein grafts occurred with regularity in all IMA implants and ACB conduits. The intimal changes were much more severe in the IMA implants as compared to the ACB conduits: There was 25 to 95 per cent liminal narrowing in the IMA implants, whereas the ACB conduits rarely showed greater than 25 per cent luminal narrowing. Both reduced flow and surgical trauma appeared to be influential determining factors of the intimal proliferative process, whereas devascularization alone seemed less important.