Platelet hyperaggregability persists even after the improvement of increased blood coagulation and impaired fibrinolysis with the stabilization of symptoms in patients with unstable angina

Background: Platelet aggregation, blood coagulation, and fibrinolysis play a pivotal role in the pathogenesis of unstable angina. Methods: Platelet ag gregability was examined on admission and after 2 weeks of treatment in 22 patients with unstable angina, in particular with regard to small-sized pla telet aggregates, plasma tissue factor (TF) antigen levels as a marker of b lood coagulation, and plasma plasminogen activator inhibitor (PAI) activity levels as an indicator of fibrinolysis. We also examined the same paramete rs in 19 patients with stable exertional angina and 17 patients with chest pain syndrome. Results: The number of small-sized platelet aggregates incre ased more significantly in the unstable angina group than in the stable exe rtional angina and chest pain syndrome groups. In the unstable angina group , the number of small-sized platelet aggregates decreased significantly aft er 2 weeks of treatment, but was still higher than that in the stable exert ional angina and chest pain syndrome groups. Plasma TF antigen and PAI acti vity were higher in the unstable angina group than in the stable exertional angina and chest pain syndrome groups. TF and PAI activity decreased to no rmal ranges after 2 weeks of treatment in the unstable angina group. There were significant positive correlations among the three parameters on admiss ion. Conclusions: It was demonstrated that small-sized platelet aggregates, plasma TF antigen and PAI activity levels increased concomitantly in the u nstable angina group. While the blood coagulation and fibrinolytic paramete rs decreased after stabilization of the clinical symptoms, platelet hyperag gregability still persisted. These results suggest that continuous antiplat elet therapy is essential for the treatment of unstable angina. (C) 2001 El sevier Science Ireland Ltd. All rights reserved.