SIGNIFICANCE OF INITIAL ST SEGMENT CHANGES FOR THROMBOLYTIC TREATMENTIN FIRST INFERIOR MYOCARDIAL-INFARCTION

Objective-To evaluate the benefit to risk ratio of thrombolytic treatm ent in patients with small inferior acute myocardial infarction (AMI). Controlled studies relating the benefit from thrombolysis with initia l electrocardiographic features are scarce and of limited sample size. Design-Retrospective study of 728 patients with a first inferior AMI of six hours' duration from the Intravenous Streptokinase in Myocardia l Infarction (ISAM) comparing streptokinase with placebo stratified by the initial sum ST segment elevation (Sigma ST) of 0.8 mV or less and greater than 0.8mV, and 636 patients from the International Joint Eff icacy Comparison of Thrombolytics (INJECT) trial comparing double blin d streptokinase with reteplase stratified by either Sigma ST or the pr esence of precordial ST segment depression. Results-ISAM study patient s with an Sigma ST of greater than 0.8 mV had a significant mortality benefit from streptokinase throughout six years, while those with an S igma ST of 0.8 mV or less showed a trend to higher mortality at six mo nths (6.3% streptokinase v 5.1% placebo). Despite significantly smalle r infarcts and fewer clinical complications in patients with an Sigma ST of 0.8 mV or less (ISAM and INJECT) or the absence of precordial ST se,ament depression (INJECT) thrombolytic treatment was associated wi th higher early mortality than in those with initially larger ST segme nt deviations. Conclusion-Thrombolytic treatment in patients with infe rior AMI presenting with larger ST segment deviations is associated wi th improved survival throughout six years. The risk to benefit ratio, however, in terms of early mortality in patients who have an CST of 0. 8 mV or less and no precordial ST segment depression may be unfavourab le.