A comprehensive estimation of acute myocardial infarct size using enzymatic, electrocardiographic and mechanical methods.

This prospective study compares the estimated size of acute myocardial infarction (AMI) by cumulative serum creatine kinase isoenzyme MB (CK-MB), Selvester QRS score, and 2-dimensional (2-D) echocardiographic dyssynergy of the left ventricle in 63 consecutive patients with their first anterior (n = 31) or inferior AMI (n = 32). The correlations among these parameters were good for patients with anterior AMI (r = 0.74 to 0.78, standard error of the estimate = 29 to 33%) but only fair for those with inferior AMI (r = 0.35 to 0.47, standard error of the estimate = 38 to 73%). Based on previous autopsy studies, estimates of CK-MB and QRS score were then converted to percent of infarcted left ventricle. Linear regression analyses between mean percent AMI size by cumulative CK-MB plus QRS score vs the number of dyssynergic segments by 2-D echocardiography were used to develop a comprehensive formula for estimating AMI size by a combination of all 3 techniques. Thus, a formula is proposed that may optimally estimate AMI size derived from leakage of cytosolic enzymes, changes in the sequence of myocardial depolarization, and irregularities of left ventricular contraction.