THERAPY AND PREVENTION

The effect of thrombolysis in acute myocardial infarction on enzymatic infarct size, left ventricular function, and early mortality was studied in subsets of patients in a randomized trial. Early thrombolytic therapy with intracoronary streptokinase (152 patients) or with intracoronary streptokinase preceded by intravenous streptokinase (117 patients) was compared with conventional treatment (264 patients). All 533 patients were admitted to the coronary care unit within 4 hr after onset of symptoms indicative of acute myocardial infarction. Four hundred eighty-eight patients were eligible for this detailed analysis, and 245 of these were allocated to thrombolytic therapy and 243 to conventional treatment. Early angiographic examinations were performed in 212 patients allocated to thrombolytic therapy. Patency of the infarct-related artery was achieved in 181 patients (85%). Enzymatic infarct size, as measured from cumulative a-hydroxybutyrate dehydrogenase release, was smaller in patients allocated to thrombolytic therapy (median 760 vs 1170 U/liter in control patients, p = .0001). Left ventricular ejection fraction measured by radionuclide angiography before discharge from the hospital was higher after thrombolytic therapy (median 50% vs 43% in control patients, p = .0001). Three month mortality was lower in patients allocated to thrombolytic therapy (6% vs 14% in the control group, p = .006). With the use of multivariate regression analysis, infarct size limitation, improvement in left ventricular ejection fraction, and three month mortality were predicted by sum of the ST segment elevation, time from onset of symptoms to admission, and Killip class at admission. Thrombolysis was most effective in patients admitted within 2 hr after onset of symptoms and in patients with a sum of ST segment elevation of 1.2 mV or more. On the other hand, no beneficial effects of streptokinase on enzymatic infarct size, left ventricular function, or mortality were observed in the subset of patients with a sum of ST segment elevation of less than 1.2 mV who were admitted between 2 and 4 hr after onset of symptoms. Circulation 74, No. 6, 1379-1389, 1986 IN APPROXIMATELY 80% to 90% of patients with acute myocardial infarction, intracoronary infusion of streptokinase given in the first hours after onset of chest pain leads to thrombolysis and recanalization of the occluded coronary artery. 1-3 From the Working Group on Thrombolytic Therapy in Acute Myocardial Infarction of the Netherlands Interuniversity Cardiology Institute. Participating centers and collaborators are listed before the references. Address for correspondence: F. Vermeer, M.D., Department of Cardiology, University Hospital Maastricht, University of Limburg, P.O. Box 1918, 6201 BX Maastricht, The Netherlands. Received April 15, 1986; revision accepted Aug. 21, 1986. Vol. 74, No. 6, December 1986 angiographically proven obstruction, without major complications. The high patency rate after thrombolysis was associated with limitation of infarct size, higher left ventricular ejection fraction (LVEF), and improved survival in comparison with these variables in conventionally treated patients. The design of this study, clinical course in the hospital, complications of early catheterization, limitation of enzymatic infarct size, and improvement in left ventricular function and survival during the follow-up period have been described elsewhere.4-7 The aim of the present analysis was to define subsets of patients that benefitted most from early recanalization. Special attention was paid to patient characteristics available early after hospital admission, such as