The European Multicentre Study (EMS) assessed coronary reperfusion, functional outcome and safety of anistreplase (anisoylated plasminogen streptokinase activator complex = APSAC) compared to a control group treated with heparin alone in patients with a clinical diagnosis of acute myocardial infarction (AMI). In the Belgian subset of data (n = 103) the reperfusion results, based on non-invasive clinical parameters, were significantly better in the APSAC group: 66% versus 18% in the heparin group (P less than 0.0001). No significant difference was found between the two treatment groups with respect to left ventricular function and adverse events. The purpose of the present study was to analyse the indicative value of ST-segment changes as a possible predictor of reperfusion in threatened myocardial tissue. Two scoring systems were used: the first was based on the combined evaluation of three clinical non-invasive parameters (course of chest pain, ECG evaluation of ST segment changes, reperfusion arrhythmias); the second was based on the changes of the sum of the ST-segment (sigma-ST) evaluations on consecutive 12-lead ECGs. There was a good correlation between the combined clinical scoring system and the residual stenosis on coronary angiography (P less than 0.05) and early CK peak (P less than 0.0001). Analysis of the ECG data revealed that a decrease of greater than or equal to 50% of the sum of ST-elevations (sigma-ST) at 2 h post-treatment in both limb and precordial leads is a fairly useful predictor of reperfusion (sensitivity = 73%, specificity = 63%, predictive value = 88%).