Coronary thrombolysis for evolving myocardial infarction.

An acute thrombus at the site of an atherosclerotic obstruction is the usual cause of myocardial infarction. Thrombolytic therapy is an exciting new therapy for reducing the extent of myocardial infarction by lysing intracoronary clots. Such therapy has now been widely applied by: prolonged intravenous infusion of streptokinase during the first 24 hours of infarction; intracoronary infusion of streptokinase, urokinase, or tissue plasminogen activator; early, high dose, brief duration intravenous infusion of streptokinase; or intravenous infusion of tissue plasminogen activator. Intracoronary streptokinase or urokinase achieves reperfusion of the coronary artery in 75% of patients and is associated with serious bleeding in 4.8% of patients. Intravenous infusion of streptokinase achieves reperfusion of the coronary artery in 50 to 80% of patients. The incidence of serious bleeding with intravenous streptokinase averaged 0.8% in 5 studies of 237 patients and was 12.8% in 1 additional study of 80 patients. Salvage of the jeopardised myocardium and improvement in left ventricular function occurred when coronary reperfusion was achieved. Mortality in streptokinase-treated patients was significantly reduced at 30 days and at 6 months after infarction in the single randomised mortality study done to date; however, more data are needed on this important question. Reocclusion after thrombolysis averages 17% in patients treated with streptokinase by either intracoronary or intravenous infusion. The newly reperfused coronary artery has been stabilised in some patients by coronary bypass surgery or percutaneous transluminal angioplasty, but further studies are needed to define criteria for appropriate patient selection for these procedures.