USE OF CHANGES IN ST SEGMENT ELEVATION FOR PREDICTION OF INFARCT ARTERY RECANALIZATION IN ACUTE MYOCARDIAL-INFARCTION

Background: The role of the ECG in evaluating reperfusion status after thrombolytic treatment in acute myocardial infarction is not clear. Dramatic ST segment changes have been observed during recanalization of an infarct-related artery, but ST criteria have not been definitively established for prediction of coronary artery patency. Differences in ST segment changes in relation to infarct localization have not been evaluated and further investigation is required into reciprocal ST depression, which provides information independent from ST elevation. Therefore, the aim of this study was to evaluate how early changes in ST segment elevations and depressions predict vessel patency after fibrinolysis for patients with anterior and inferior/lateral infarcts. Methods and Results: Two hundred patients with a Pardee wave in the ECG and chest pain of less than 6 h duration were given thrombolytic treatment. The result of the therapy was assessed simultaneously with coronary angiography. Patients were divided into two groups. I (50 patients) without recanalization (TIMI grade 0, 1 or 2), and II (150 patients) with successful recanalization (TIMI grade 3). Before and after therapy, analysis of the 12 lead ECG included maximum ST elevation measurement (H-1, H-2 respectively), the sum of ST elevation (Sigma H-1, Sigma H-2), the sum of ST segment depressions (Sigma h(1), Sigma h(2)), and the ratios of ST segment changes (R-1=H-2:H-1, R-2=Sigma H-2:Sigma H-1, R-3=Sigma h(2):Sigma h(1)). The mean interval from the first to the second ECG was 3.5 +/- 1 h. Successive values of R-1 and R-2 were examined to find that which best distinguished between the two groups. The best values for prediction of reperfusion were: (1) For anterior wall infarct Specificity Sensitivity R-1 less than or equal to 0.6 83.3% 88.7% R-2 less than or equal to 0.5 83.3% 92.0% (2) For inferior and lateral infarct R-2 < 0.5 100% 93.8% R-2 < 0.5 100% 92.8% In 13 patients with a complete right ol left bundle branch block in the fir st or second ECG, the result of treatment was predicted in 11 patients using criteria for factor R-1 and in 12 patients using criteria ia for R-2. Analysis of ST segment depressions revealed a significant correlation between normalization of ST segment depressions and elevations (R-3 vs R-1:r=0.60, P<0.05; R-3 vs R-2 r=0.59, P<0.05). Multivariate discriminant analysis showed an independent value of R-3 for discrimination between the two groups, but only in patients with inferior/lateral infarcts. The overall accuracy of the common algorithm in predicting reperfusion was significantly better in patients with inferior/lateral infarcts (Chi(2) test, P=0.0078). When separate algorithms were used, there was no significant difference between patients with anterior or inferior/lateral infarcts because of the significant improvement in prediction of reperfusion in patients with anterior infarcts (McNemar's test: P=0.041). Conclusions: We conclude that analysis of ST segments on the standard 12-lead ECG offers valuable help in the early identification of successful rcanalization of infarct-related arteries after thrombolytic therapy in patients with acute myocardial infarction. Use of the ratio of ST segment normalization according to the separate criteria for anterior and inferior/latelal infarcts gives the test a high sensitivity and specificity, even in the presence of interventricular conduction disturbances.