Thrombosis and cardiovascular disease.

The early stages of venous thrombosis originate at selective sites of reduced blood flow in the apices of venous valves. Stagnation of venous flow results in the formation of a platelet-fibrin thrombus, which serves as the nidus for thrombus propagation. Stasis alone, however, does not result in thrombosis necessarily. The presence of activated coagulation factors is essential. The major predisposing factors to venous thrombus are activation of blood coagulation and venous stasis. In contrast to venous thrombus formation, vascular abnormalities are the most important causative factor in arterial thrombosis.