Thrombolytic Therapy in Acute Myocardial Infarction

Early thrombolytic therapy has been shown to reduce hospital mortality after myocardial infarction by 20-50%. This is achieved through reperfusion of the ischemic myocardium, which leads to limitation of infarct size by 15-30% and preservation of regional and global left ventricular function. Thrombolysis and reperfusion can be achieved by intravenous administration of streptokinase, urokinase, APSAC, or rt-PA, or by intracoronary administration of streptokinase or urokinase. Thrombolytic therapy is most effective in patients with extensive myocardial ischemia (large infarction) treated early after the onset of symptoms, but also patients with smaller infarcts may benefit from the therapy. It is uncertain whether treatment later than six hours after the onset of symptoms is beneficial, and if so, in which patients. Thrombolytic therapy leads to bleeding complications in a minority of patients. The risk of intracranial bleeding is approximately 0.5%. However, in several large trials the rate of cerebrovascular accidents (bleeding plus embolism) was not higher after thrombolytic therapy with streptokinase or rt-PA than after placebo. In order to prevent rethrombosis, additional treatment with acetyl salicylic acid and heparin is recommended. Nitrates and antiarrhythmic drugs are not recommended as routine practice. Immediate PTCA does not improve patient outcome. At present angiography and subsequent angioplasty or bypass surgery is recommended in patients with recurrent ischemia (spontaneous or upon exercise) after the infarct.