Laboratory markers of hypercoagulability.

Investigations carried out over the last 40 years have demonstrated that coronary artery thrombosis is the critical event underlying myocardial infarction and unstable angina. The existence of a prolonged hypercoagulable state preceding the thrombotic event has been postulated for some time and significant associations have been established between the plasma concentrations of a number of hemostatic variables and the frequency of myocardial infarction. High plasma fibrinogen, factor VII/VIIa, tissue-type plasminogen activator and plasminogen activator inhibitor levels have been associated with at least as great a risk of developing myocardial (re)infarction or sudden death as high cholesterol levels, especially in the young. In the last year more sensitive assays have been developed, and they should allow a precise biochemical definition of hypercoagulable states. The significance of these new assays and their role in defining a hypercoagulable state in different conditions are analyzed.