Enhanced platelet function in acute myocardial infarction is attenuated by streptokinase treatment.

The aim of this study was to determine whether platelets are activated and aggregation is increased in myocardial infarction treated with streptokinase. Twelve consecutive patients were studied. Before streptokinase infusion (1.5 x 10(6) IU i.v. over a period of 1 h), 7 +/- 4 h after the onset of symptoms, fibrinogen, leucocyte and platelet functions were enhanced compared to reference values. Plasma fibrinogen was 3.1 +/- 0.6 g 1-1 (P less than 0.03), leucocyte count was 14.3 +/- 3.3 x 10(3) l-1 (P less than 0.0005), elastase was 39 +/- 8 micrograms l-1 (P less than 0.0002), beta-thromboglobulin was 68 +/- 71 micrograms 1-1 (P less than 0.0001) and filtragometer platelet aggregation time was 137 +/- 40 s (P less than 0.0001). After streptokinase the leucocyte count, elastase and beta-thromboglobulin levels increased further, by about 40% (P less than 0.02), 130% (P less than 0.02) and 140% (P less than 0.005), respectively. Fibrinogen was almost eliminated. Despite signs of increased activation, platelet aggregation was decreased as indicated by both filtragometer aggregation time, which increased by about 480% (P less than 0.003), and whole-blood aggregometry, in which electrical impedance decreased by about 65% (P less than 0.01).