Thrombus formation and dissolution is a continuous process in the vasculature and is regulated by dynamic interactions between pro-coagulant and pro-fibrinolytic factors. Endogenous fibrinolysis is determined by the relative balance between the acute local release of t-PA from the endothelium and its subsequent inhibition by plasma plasminogen activator inhibitor type 1 (PAI-1). In the presence of an imbalance in the fibrinolytic system, subclinical microthrombi on the surface of atherosclerotic plaques may propagate and ultimately lead to arterial occlusion and tissue infarction.