Fibrinolysis and thrombosis

The fibrinolytic system generates plasmin, which dissolves fibrin in haemos tatic plugs and in thrombi. It is often regarded simply as a secondary phen omenon responsive to the generation of thrombi but it is, rather, in dynami c balance with fibrin formation, such that abnormalities in either can lead to thrombosis. This chapter summarizes the fibrinolytic system and its reg ulation. It considers the components of the system in blood, both in plasma and in circulating cells, with emphasis on protease-inhibitor balance. It goes on to discuss local fibrinolytic potential in thrombi, both venous and arterial, and in the diseased vessel wail, presenting evidence that increa sed local inhibition of fibrinolysis by PAI-1, PAI-2 and alpha(2)-antiplasm in is intimately involved in thrombus stability and in the generation of fi brin-rich vessel wall lesions. Finally, it reviews the evidence that defect ive plasma fibrinolysis has a causal role in venous and arterial thrombosis .