Value of admission electrocardiogram in predicting outcome of thrombolytic therapy in acute myocardial infarction

To determine the value of the admission 12-lead electrocardiogram to predict infarct size limitation by thrombolytic therapy, data were analyzed in 488 of 533 patients with acute myocardial infarction (AMI) from a randomized multicenter study. All patients had typical electrocardiographic changes diagnostic for an AMI and were admitted within 4 h after the onset of chest pain; 245 patients were allocated to thrombolytic treatment and 243 to conventional treatment. Cumulative 72-h release into plasma of myocardial ±-hydroxybutyrate dehydrogenase (HBDH) was used as a measure of infarct size. In general, the amount of infarct limitation due to thrombolytic therapy was proportional to the size of the area at risk. Patients with new Q waves, high QRS score and high ST-segment elevation or depression had the largest enzymatic infarct size in both treatment groups, irrespective of location of the AMI. Compared with conventionally treated patients, patients with anterior AMI treated with streptokinase had significant infarct size limitation (480 U l-1 HBDH, 37%) and limitation was most prominent in those with Q waves (820 U l-1 HBDH) or high ST elevation (750 U l-1 HBDH). Infarct size limitation in inferior AMI was less impressive (330 U l-1 HBDH, 33%) and patients with high ST-segment elevation (460 U l-1 HBDH) or marked contralateral ST-segment depression (430 U l-1 HBDH) had the most notable infarct limitation. Independent of interval between onset of chest pain and admission, in both types of AMI no significant infarct limitation was seen in patients with low ST elevation in the absence of Q waves, while in those with high ST elevation, in the presence but especially in the absence of Q waves, thrombolytic therapy was effective. Thus, thrombolytic therapy is most potent in patients with AMI admitted early after onset of chest pain who have electrocardiographically a large infarcted or ischemic area.