Prognostic Value of ST-Elevation

To the Editor: The paper by Nielsen in the August 1973 issue of "Circulation"' on the prognostic importance of the ST segment elevation in acute myocardial infarction touches a point which has not been dealt with in the literature heretofore: the quantitative assessment of the ST segment elevation in the 12 lead standard ECG. The latter has been only qualitatively utilized in the diagnosis of myocardial infarction, although changes of the magnitude of ST shifts elevation or depression have long been suspected by the practicing physician to reflect changes in the clinical status of patients. Good correlation between sums of ST shifts and magnitude and extent of ischemic injury have been demonstrated in several studies.2-6 Follow-up of patients with myocardial infarction has been facilitated, and extension of the initial ischemic damage has been detected using various precordial mapping systems.2-6 The question arises if the standard 12 lead ECG can similarly be used as an objective index of ischemic injury. Nielsen has found good correlation of the magnitude of ST elevation and prevalence of cardiac arrest, congestive heart failure, death, shock and certain arrhythmias, and conduction defects, using the standard 12 lead ECG.' These correlations existed despite the fact that a random baseline ECG was used for the analysis, and no serial studies were done. Some information is presently available regarding the relative merits of the 49-lead and conventional 12lead systems in evaluating both magnitude and extent of ischemic injury. In a systematic comparison of the two systems, we have demonstrated the superiority of the 49-lead system in assessing magnitude of ischemic injury.' Similarly, Reid and his colleagues noted that extension of infarction was detected by 48-lead maps in a considerable number of patients in whom changes were absent in the conventional 12-lead ECG (fully one-third of a series of 12 patients). Thus, although the standard ECG "scans" only a fraction of the recording sites of the mapping system,2' the study of Nielsen should stimulate clinicians to look at the standard ECG in a more quantitative fashion, since mapping techniques have not