Usefulness of thrombolytic therapy with low doses of streptokinase in acute myocardial infarction

Background: The optimal dose of Streptokinase in the treatment of acute myocardial infarction is not well established. Apparently, the thrombolytic efficacy would not increase with doses over 750.000 units. Aim: To compare the effectiveness and safety of treatment with low doses of Streptokinase, ranging from 500.000 to 750.000 units, in patients with ST elevation acute myocardial infarction. Patients and methods. From September 1993 to September 1998, the GEMI register of patients with acute myocardial infarction, was carried out in 3 7 hospitals, incorporating 4,938 patients. Of these, 1,631 patients received streptokinase. According to the administered dose of Streptokinase, patients were divided in two groups: 1, 465 patients who received 1.5 millions U in 60 minutes (classical therapy group), and 166 patients with ischemic chest discomfort and either ST-segment elevation or left bundle-branch block on the electrocardiogram, who received 500.000 to 750.000 U streptokinase administered in no more than 30 minutes, with heparin, within 0 to 6 bouts of symptom onset. Successful reperfusion, mortality, complications, and hospital outcome was evaluated in both groups. Results. The low dose group of patients bad a better reperfusion criteria profile. No differences between groups were observed in patient evolution, mortality, maximum Killip classffication, post myocardial infarction heart failure, ischemic complications, arrhythmias or mechanical complications. Conclusions: These results suggest that streptokinase in low doses is at least as effective as classical therapy, in the treatment of ST elevation acute myocardial infarction.