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Morbidity and long-term mortality following acute myocardial infarction are directly related to the extent of left ventricular dysfunction. None of the numerous interventions that have been explored in the prevention of myocardial necrosis appears to surpass the benefit provided by rapid restoration of blood flow in the infarct-related coronary artery and attendant reperfusion of the ischemic zone. Although intracoronary administration of thrombolytic drugs results in rapid recanalization (72% with streptokinase or urokinase, 65% with APSAC), this route of administration is not practical and probably not necessary. Indeed, with intravenous administration of thrombolytics, the recanalization rate determined 90 min after the start of 1.5 million U of streptokinase is 43%, after 30 U of APSAC is 56%, after 1 to 2 million U of urokinase is 53%, and after rt-PA is 69%, Coronary patency can be achieved by intravenous therapy, with rates at 90 min of 56% for SK, 77% for APSAC, 71% for pro-urokinase, and 75% for rt-PA. There is sufficient evidence at present to conclude that the early administration of a thrombolytic agent will reduce infarct size and promote improved ventricular function. The benefits afforded by early recanalization on ejection fraction are clear and unmistakable. When compared to placebo treatment, the hospital mortality reduction in patients treated within 6 h after onset of symptoms is 47% after intracoronary SK, 43% after intravenous SK. 48% after intravenous APSAC, and 51% after intravenous rt-PA. However, the results of direct comparison of these different thrombolytic agents on the left ventricular function and mortality in a large number of patients are crucially important and eagerly anticipated.