[Usefulness of the 12-lead standard electrocardiogram in assessing myocardial infarct size]

The value of the electrocardiogram in assessing infarct size was studied using serial estimates of serum creatine phosphokinase (CPK) in serum and serial 12-lead electrocardiograms in patients admitted to a coronary care unit with acute myocardial infarction. Sum of the ST segment deviations from the isoelectric line (sigma ST12) and sum of the conventional scores of Q waves amplitude (sigma Q12) were obtained from each electrocardiogram, and then the time-course of these parameters was considered. The correlation between maximum sigma Q12 and CPK-peak in anterior infarcts, was highly significant (r = 0.733; P less than 0.001). Maximum sigma ST12, measured upon admission or immediately thereafter in patients hospitalized within 4 hours from the onset of chest pain, was found to correlate significantly with CPK-peak (r = 0.675, P less than 0.001 for the whole group; r = 0.758, P less than 0.01 for patients with inferior infarcts). Time-course of sigma ST12 and CPK showed 4 different patterns. Among them, type 1 ("rapid necrosis") showed the most significant correlations (maximum sigma ST12 within 4 hours from symptoms versus CPK-peak: r = 0.909, P less than 0.001; maximum sigma Q12 versus CPK-peak in anterior infarcts: r = 0.782, P less than 0,05; and maximum sigma ST12 within 4 hours from the onset of pain versus sigma Q12 in patients with anterior infarcts: r = 0.863, P less than 0,05). There was no correlation between sigma ST12 at any other time and CPK-peak: this observation is in accordance with the presence of a rapid decrease in the mean sigma ST12 after the first 3-4 hours from the beginning of symptoms. This study shows that the analysis of ST segment deviations and of Q waves development in the standard electrocardiogram provides useful information on the size of acute myocardial infarction as reflected by the peak value of serum CPK.