[Histopathology of thrombotic vascular diseases]

Three principal factors predispose to thrombus formation (Virchow's triad): (1) endothelial injury, (2) stasis or turbulence of blood flow, and (3) blood hypercoagulability. Endothelial denudation is the most important factor, especially in the development of arterial thrombus. Arterial thrombi are frequently occlusive, and the most common sites are coronary, cerebral, and femoral arteries. The thrombi induce severe ischemia or infarction of the heart, brain, and lower extremities. The thrombi are usually superimposed on an atherosclerotic plaque. Plaque rupture or erosion is considered to be the trigger of acute thrombus formation. While venous thrombi are invariably occlusive, and commonly affect the lower extremities. Static blood flow, phlebitis, and genetic and acquired hypercoagulability often contribute to venous thrombosis.