Significance of Initial ST Segment Elevation and Depression for the Management of Thrombolytic Therapy in Acute Myocardial Infarction

To determine the ability of initial ST segment elevation and depression to predict infarct size limitation by thrombolytic therapy, data were analyzed in 721 patients with acute myocardial infarction who were admitted to a randomized, placebo-controlled study of intravenous recombinant tissue-type plasminogen activator. Patients with QRS duration of 120 msec or more or with previous history ofmyocardial infarction were excluded, leaving 322 in the treatment and 333 in the placebo group. Cumulative 72-hour release of G.hydroxybutrate dehydrogenase and global ejection fraction as well as left ventricular wail motion derived from angiography were used as independent measures of infarct size. Electrocardiograms obtained at admission, 6 hours after start of therapy, and before discharge were analyzed. All ST measurements were made by hand at the J point and 60 msec after the J point. Patients with high ST segment elevation at admission (i.e., sum of ST elevation at 60 msec after the J point was 20 mm or more) had significantly larger infarction and higher hospital mortality when compared with those with lower (<20 mm) ST elevation. Reciprocal ST segment depression also showed a linear relation with infarct size and mortality, independent from ST elevation, both in anterior and inferior myocardial infarction. The sum of deviations measured at the J point and 60 msec after the J point differed significantly, especially in anterior myocardial infarction at admission (mean, 16±9 versus 23±11 mm). The prognostic value of one measurement was not, however, superior over the other. Treatment with recombinant tissue-type plasminogen activator was most effective in those with large ST deviations at admission, but patients with anterior infarction and smaller ST shifts also appeared to benefit from therapy. Results in individual patients were variable, and the overall correlation of initial ST shifts with enzymatic infarct size was rather low. In conclusion, the present study shows that the magnitude of initial ST elevation and also of reciprocal ST depression in the admission electrocardiogram is valuable for the management and assessment of thrombolytic therapy in patients with acute myocardial infarction. (Circulation 1990;82:1147-1158)