In patients with excessive venous thrombosis, genetic defects predisposing to thrombosis can be found in 60-80%. Increased plasma levels of coagulation proteins such as fibrinogen and plasminogen activator inhibitor-1 (PAI-1) are associated with an increased risk of myocardial infarction. However, despite the presence of polymorphisms that regulate plasma levels of factor VIII, PAI-1, and fibrinogen the association between common polymorphisms of these coagulation protein and ischemic cardiac disease remains ambiguous. Up to 10% of the population have defects that predispose them to excessive venous thrombosis. In spite of the essential role of thrombosis in coronary ischemic syndrome, no convincing evidence has implicated the two most common venous hypercoagulable states in ischemic heart disease. Pathogenic polymorphisms in the platelet fibrinogen and collagen receptors remain an area of intense research interest. Finally, it has been shown that lipoproteins can act as mediators Of coagulation processes. Curr Opin Lipidol 10:443-448. (C) 1999 Lippincott Williams & Wilkins.