[Mechanism of coronary bypass graft disease].

Clinical studies on the patency rate of different coronary bypass vessels suggest that biological properties importantly influence graft function. As regards function and patency of coronary bypass vessels, proliferative responses, antithrombotic properties, and vasomotion play important roles. Thrombotic processes are responsible for acute closure of grafts, particularly in the context of reduced endothelial function or surgical trauma to the endothelium. The internal mammary artery and gastroepiploic artery release significantly more factors with antithrombotic and antispastic properties, such as nitric oxide (the endogenous nitrovasodilator) and prostacyclin than the saphenous vein. Structural changes to bypass grafts are related to proliferation and migration of vascular smooth muscle cells. Vascular smooth muscle cells of the saphenous vein exhibit particularly pronounced proliferative responses to pulsatile stretch and platelet-derived growth factor, while cells obtained from the internal mammary artery respond poorly to these stimuli. These different biological properties of the endothelium and vascular smooth muscle cells may contribute importantly to the excellent patency rate of internal mammary artery grafts, while those constructed with the saphenous vein exhibit thrombotic occlusions and proliferative changes.