Use of initial ST-segment deviation for prediction of final electrocardiographic size of acute myocardial infarcts

The decision to administer thrombolytic therapy for limitation of acute myocardial infarction (AMI) size must occur when only the history, physical examination and 12-lead electrocardiogram of a patient are available. A method that could quickly assess the amount of jeopardized myocardium would greatly aid the physician. This study developed formulas from 68 anterior and 80 inferior AMI patients using the extent of initial ST-segment deviation (STΔ) to predict the final AMI size estimated by the Selvester QRS score in a population not receiving reperfusion therapy. Inclusion required: initial anterior or inferior AMI; admission electrocardiograpm ≤8 hours after the onset of symptoms with evidence of epicardial injury; elevated creatine kinase-MB; a predischarge electrocardiogram taken ≥72 hours after admission; and no AMI extension before the predischarge electrocardiogram. The extent of epicardial injury was quantified by counting the number of leads with ≥0.1 mm STΔ, by the sum (Σ) of STΔ in all leads and by the ΣSTΔ in the lead groups associated with each AMI location. These results were compared to the AMI size estimated from the predischarge electrocardiogram. Univariable and multivariable analyses generated these formulas for AMI size: anterior = 3[1.5(number leads ST↑) −0.4]; inferior = 3[0.6(ΣST↑ II, III, aVF) +2.0]. Thus, formulas based on quantitative measurements of STΔ on the admission electrocardiogram are predictive of final QRS-estimated AMI size, and may be useful in determining the efficacy of acute reperfusion therapy.