Thoughts About the Abnormalities in the Electrocardiogram of Patients with Acute Myocardial Infarction with Emphasis on a more Accurate Method of Interpreting ST‐segment Displacement: Part I

Abstract

The QRS, S‐T, and T wave abnormalities produced by the usual myocardial infarction are discussed in Part I of this manuscript.The recent guidelines supplied by the ACC/AHA Practice Guidelines divide primary S‐T segment displacement into S‐T segment elevated myocardial infarction (STEMI) and non S‐T segment elevated myocardial infarction (NSTEMI). Accordingly, the electrophysiologic mechanisms responsible for epicardial and subendocardial injury that produce the S‐T segment abnormalities are discussed in this manuscript. In this regard, the author suggests that the Grant method of interpreting the 12 lead electrocardiogram, which uses basic principles and vector concepts, is a more accurate method of identifying epicardial injury and subendocardial injury than memorizing the rules provided by the guidelines. An electrocardiogram is shown to illustrate this point. In Addition, the author expresses his personal view that labeling an electrocardiogram as NSTEMI but not stating what is actually present in the tracing is a cumbersome method of communication. The author believes it is better communication to state what is present rather than to state what is not present. At best, the result of both assessments should be stated in the interpretation.Part II of the manuscript is devoted to a discussion as to why treatment with thrombolytic or percutaneous coronary intervention is more effective in patients whose electrocardiograms reveal epicardial injury than it is in patients whose electrocardiograms reveal subendocardial injury or no injury. Copyright © 2007 Wiley Periodicals, Inc.

Total coronary occlusion of infarct-related arteries in patients with non-ST-elevation myocardial infarction undergoing percutaneous coronary revascularisation

“…Acute total occlusion in the IRA causes transmural ischaemia that generates a mean spatial ST vector directed toward the area of the predominant epicardial injury, which results in ST-segment elevation. In contrast, subendocardial ischaemia caused by a transient coronary occlusion or microembolisation with components of a non-occlusive thrombus might result in "electrical silence" or ST-segment depression [3,9]. Current clinical guidelines take into account this phenomenon and recommend urgent revascularisation only in patients with STEMI [1].…”

Pseudo-Normalization of the T-wave During Stress and Its Relationship With Myocardial Ischemia: Evaluation by Myocardial Perfusion Single Photon Emission Computed Tomography (SPECT)

“…However, some studies report that, in a previously infarcted heart, this same pseudo-normalization can be associated with viable myocardium or recovery of segmental mobility [9][10][11]. Nevertheless, results can be disparate when the sensitivity and specificity to predict myocardial recovery are low [12]. One important point to be kept in mind is that the studies performed for detecting ischemia in patients who normalized the T-wave after exercise was carried out nearly 30 years ago, with several diagnostic limitations.…”