Prolonged streptokinase infusion in patients with unstable angina: Results of a randomized, placebo-controlled clinical trial

Background: The purpose of this study was to assess the efficacy both of prolonged (48 h) and of short-duration (1 h) administrations of streptokinase in patients with unstable angina. In unstable angina, thrombosis is a dynamic process that waxes and wanes for hours and even days. The majority of previous studies have investigated the efficacy of short-duration thrombolytic regimens. Methods: One hundred patients with acute unstable angina were randomly allocated to receive placebo, 1 500 000 U streptokinase during 1 h or 250 000 U streptokinase during 1 h and then a prolonged infusion of 100 000 U for the next 48 h. All of the treatments included intravenous heparin administration for 72 h. Results: No death occurred in the study population. One of 34 patients treated with placebo (2.9%), three of 33 treated with streptokinase during 1 h (9.0%) and three of 33 treated with streptokinase during 48 h (9.0%) had a myocardial infarction. Refractory angina occurred in nine, three and seven patients receiving placebo, streptokinase during 1 h and streptokinase during 48 h, respectively. Kaplan- Meier analysis showed that the total probability for a patient to be free of cumulative events did not differ among the three groups of patients (NS). Fourteen patients (41%) receiving placebo, 15 patients (45%) receiving streptokinase during 1 h and 14 patients (42%) receiving streptokinase during 48 h had ischaemic episodes detected by Holter monitoring during the first 72 h after hospital admission (NS). Two patients receiving streptokinase during 48 h required blood transfusion, and a greater incidence of minor bleeding (P <0.05) and adverse events (P <0.02) was observed in patients receiving prolonged streptokinase administration than in those receiving streptokinase during 1 h or placebo. Conclusions: In patients with acute unstable angina, the administration of two different regimens of streptokinase significantly reduces the probability neither of developing cardiac events during hospitalization nor of ischaemia detected by Holter monitoring in the early phase after hospital admission. Although the sample size of the study provided sufficient power to exclude only a large difference in effect size, it did allow us to detect a significantly higher incidence of bleeding in the group of patients treated with prolonged streptokinase infusion.