LABORATORY EVALUATION OF FIBRINOLYSIS IN PATIENTS WITH A HISTORY OF MYOCARDIAL-INFARCTION

The aims of this study were to determine whether elevated plasminogen activator inhibitor type 1 (PAI-1) activity after myocardial infarctio n reflects baseline PAI-1 or represents an acute-phase response second ary to the infarction, and to determine how tissue plasminogen activat or (t-PA) activity and total t-PA antigen levels in healthy control su bjects differ from those in patients after myocardial infarction. Comp ared with healthy control subjects, patients studied 1-3 months after infarction had elevated levels of PAI-1 activity and fibrinogen but no rmal levels of C-reactive protein and von Willebrand factor antigen, w hereas patients with a noncardiac acute-phase response showed elevatio n of all four proteins. Elevated PAI-1 activity in the absence of elev ations in other acute-phase proteins suggests an intrinsic increase in PAI-1 secretion in the post-myocardial infarction group. In addition, when compared with healthy control subjects, post-myocardial infarcti on patients had higher levels of total t-PA antigen (bound and free t- PA) but lower t-PA activity and a lower percentage of active t-PA. Ove rall, survivors of myocardial infarction have reduced t-PA activity an d increased PAI-1 activity that is not due to a prolonged acute-phase response.