Platelet adherence to the endothelium begins the process of intimal hyperplasia that later causes SVG atherosclerosis.103,105 After adhering to the intima, the platelets release mitogens that stimulate smooth muscle cell migration, leading to intimal proliferation and hyperplasia. Lipid is incorporated into these areas of intimal hyperplasia, resulting in atherosclerotic plaque forma- tion.106 The perioperative administration of aspirin and dipyr- idamole improves early ( 1 month) and 1-year SVG patency and decreases lipid accumulation in the SVG intima.103,106,107 2.1.4.2. Internal Mammary Arteries Unlike SVGs, IMAs usually are patent for many years postoperatively (10-year patency 90%)89,95,102,108 117 be- cause of the fact that 4% of IMAs develop atherosclerosis, and only 1% have atherosclerotic stenoses of hemodynamic significance.118 120 This resistance to the development of atherosclerosis is presumably due to 1) the nearly continuous internal elastic lamina that prevents smooth muscle cell migration and 2) the release of prostacyclin and nitric oxide, potent vasodilators and inhibitors of platelet function, by the endothelium of IMAs.119,121,122 The disadvantage of using the IMA is that it may spasm and eventually atrophy if used to bypass a coronary artery without a flow-limiting stenosis.89,95,118,123 130 Observational studies suggest an improved survival rate in patients under- going CABG when the LIMA (rather than an SVG) is used to graft the LAD artery86 88; this survival benefit is independent of the patient s sex, age, extent of CAD, and LV systolic function.87,88 Apart from improving survival rate, LIMA grafting of the LAD artery reduces the incidence of late MI, hospitalization for cardiac events, need for reoperation, and recurrence of angina.86,88 The LIMA should be used to bypass the LAD artery provided that a contraindication to its use (eg, emergency surgery, poor LIMA blood flow, subclavian artery stenosis, radiation injury, atherosclerosis) is not present. 