Decreased Plasma Fibrinolytic Potential As a Risk for Venous and Arterial Thrombosis

It has been well established that inherited or acquired hypercoagulability is a risk factor for venous thrombosis. In addition, hypercoagulability may contribute to the risk of arterial events. Much less is known regarding the role of the fibrinolytic system in the risk of thrombotic disease, which partly relates to the lack of validated assays. A plasma-based global fibrinolysis assay, which is sensitive to plasma levels of plasminogen, regulators of fibrinolysis, and proteins involved in coagulation, has been used in large epidemiological studies to assess the role of fibrinolysis in thrombosis. It has been demonstrated that a hypofibrinolytic state increases the risk of a first venous thrombosis, but not of a recurrence. This increased risk of venous thrombosis associated with plasma hypofibrinolysis appears primarily driven by elevated plasma levels of thrombin-activatable fibrinolysis inhibitor and plasminogen activator inhibitor type 1. The combination of hypercoagulability and hypofibrinolysis synergistically enhances the risk of a first venous event. Plasma hypofibrinolysis may constitute a risk factor for the postthrombotic syndrome. Decreased fibrinolytic potential is also associated with an increased risk of arterial thrombosis, but only in individuals younger than 55 years. The association between hypofibrinolysis and myocardial infarction appears primarily driven by elevated levels of α₂-antiplasmin. Although recent studies have clearly demonstrated a role of the fibrinolytic system in thrombotic disease, the clinical utility of plasma-based clot lysis assays is probably limited.