Thrombolytic therapy: then and now.
Although thrombolytic agents were discovered nearly 60 years ago, it is only within the past decade that the clinical use of these agents has revolutionized the treatment of acute myocardial infarction. There are four currently available agents approved for use in treatment of myocardial infarction: streptokinase, urokinase, tissue plasminogen activator, and anistreplase. Although each of these agents works in a unique fashion, the common end point of therapy is the dissolution of a fibrin clot by the conversion of plasminogen to plasmin. A number of clinically measurable end points have been used to determine the effectiveness of these agents in the treatment of acute myocardial infarction, including mortality, reperfusion, patency, left ventricular function, left ventricular volumes, and quantitative creatine kinase isoenzyme analysis. Secondary end points have included bleeding and stroke, as well as recurrent ischemic events. Numerous clinical studies have demonstrated the effectiveness of all of these agents in achieving the desired end points and comparative studies, including several large-scale trials, have failed to differentiate among these agents with regard to efficacy. Newer dosing regimens for currently available thrombolytic agents, as well as new thrombolytic agents, are currently under active investigation and will be the subject of intense research over the next few years. Despite the lack of consensus as to which agent is superior, it is clear that thrombolytic therapy for acute myocardial infarction is the treatment of choice.