Late patency of the internal mammary artery as a coronary bypass conduit.

From January, 1972, through August, 1977, 472 patients had internal mammary artery (IMA) coronary bypass, of which 100 were double-IMA bypasses. We selected those patients having a widely patent IMA one year postoperatively who then had a second catheterization 49 to 105 (mean, 64) months following operation. None of the 93 patients who met these criteria was specifically recalled for this study; they all had follow-up catheterizations for multiple other reasons. All of the 91 left IMA and 22 right IMA bypasses (total, 113) were patent at late catheterization, but 1 right IMA was diffusely narrowed. One left IMA had acute angulation with 50% stenosis proximal to the distal anastomosis, which was unchanged over the follow-up interval. There were 100 patent saphenous vein bypasses at one year and 87 at late catheterization. Late closure of coronary bypass grafts is secondary to progression of coronary disease, atherosclerosis of the bypass conduit, or intimal proliferation. Because we have not encountered the latter two causes of conduit closure, IMA grafts remain our graft of choice for nonemergent operations in patients under 60 years of age having revascularization of the left anterior descending coronary artery system.