Evidence for Reduced Fibrinolytic Activity in Unstable Angina at Rest

Background. The goal of this study was to evaluate the role of the fibrinolytic system in patients with unstable angina at rest associated with transient electrocardiographic changes. Methods and Results. Tissue plasminogen activator activity in plasma was comparable among patients with unstable angina (n = 17), patients with stable exertional angina (n = 10), and control patients with normal coronary arteriograms (n=8). In contrast, plasminogen activator inhibi-tor-1 (PAI-1) activity in plasma was elevated in the unstable angina group (21.67±+9.52 AU/mi) as compared with either the stable angina group (12.01±+7.06 AU/mil, p<0.02) or the controls (12.49±8.54 AU/mil, p<0.02). Coronary angiography performed within 24 hours after the last anginal episode showed a similar extent of coronary artery disease in the unstable and stable angina groups. However, intracoronary thrombi were observed in eight patients in the unstable angina group while no thrombus was noted in the stable angina group (,2=7.22, p <0.01). Conclusions. We conclude that patients with unstable angina at rest have a reduced fibrinolytic activity and an increased incidence of intracoronary thrombi. It is postulated that elevated PAI-1 activity in the presence of coronary arterial wall injury may be an important factor leading to the development of acute coronary syndromes. (Circulation 1991;83:1685-1691