Effectiveness of intravenous streptokinase on infarct size and left ventricular function in acute myocardial infarction, prospective and randomized study

Within 3 h after the onset of symptoms of myocardial infarction, 64 patients were randomly assigned to receive either a 1-h intravenous infusion of 1,500,000 IU of streptokinase (SK) or a conventional therapy. Infarct size was estimated in CK gram equivalent (CKg) by measurement of CK-MB every 3 hours during a 48-h period. Enzymatic study revealed that myocardial infarction of the SK group was significantly smaller (61.4±45 vs. 89.4±56 CKg, p< .05). Angiograms were performed at early stage and five weeks after myocardial infarction. At first coronary angiogram, the infarct-related vessel was open in 82% in the SK group versus 12% in controls. The SK group had higher global ejection fraction at second angiogram (57±11% vs. 49±11%, p<.02), but differences in regional wall motion were not significant. By analysis according to patency or occlusion of infarctrelated vessel, global and regional ejection fractions were significantly better at first and at second angiograms in all patients and in anterior infarctions with a patent infarctrelated coronary artery. There was no significant difference for inferior infarction. We conclude that intravenous streptokinase infusion early after the onset of myocardial infarction reduces infarct size and improves left ventricular function, chiefly in anterior infarction. This benefit appears to be closely correlated to patency of infarct-related vessels.