Incidence of atherosclerosis in the internal mammary artery.

The long-term patency of the internal mammary artery (IMA) graft is better than that of the saphenous vein graft in coronary bypass procedures. The better patency is thought to be due in part to a relatively low incidence of atherosclerosis in the IMA. In the present study, the incidence of atherosclerosis in the IMA was evaluated in a consecutive Finnish autopsy series of 160 patients. Forty-five patients (28%) had marked occlusion in some coronary arteries as well as a history of angina pectoris. Only 5 (3.1%) of the 160 patients had notable stenosis in the IMA. Three of these 5 patients did not have coronary heart disease. Macroscopic or microscopic signs of atherosclerosis were found in 12.4% of 314 IMAs. We conclude that the low incidence of atherosclerosis in the IMAs in our study is due to their good resistance to the sclerotic process, although the incidence of ischemic heart diseases in Finland is among the highest in the world.