Is it time for change

Newer in vivo imaging techniques such as contrastenhanced magnetic resonance imaging (MRI) are proving very useful in defining cardiac anatomy and pathology and serving as the gold standard for more indirect biochemical, electrical, and mechanical markers such as the various blood tests, electrocardiography and radiograph, and nuclear ventriculography. In this issue of the Journal, Bayes de Luna and colleagues employ contrast-enhanced MRI, performed in patients 3 to 6 weeks after an acute ST elevation myocardial infarction to test the sensitivity and specificity of ECG criteria involving the amplitude and duration of the R wave in leads V1 and V2 and the R-S ratio in these leads, as well as the polarity and amplitude of the T wave in V1 and V2 to diagnose infarctions involving regions that they identify as lateral, inferior, or inferolateral. The authors' use of the terms and the ECG criteria to describe regions that are more usually referred to as “posterior” and “inferoposterior” 1-4 is based on their previous observations. 5 The authors make a convincing argument that an R-S ratio in V1 exceeding 0.5 provides greater sensitivity for the diagnosis of a lateral (or posterior) wall infarction than the previously used criterion of greater than 1 without loss of specificity. They also show that an R wave greater than 3 mm discriminates between infarctions involving the lateral (or posterior) wall from that involving the inferior wall, and they confirm the sensitivity and specificity of an R wave duration greater than40millisecondsindiagnosing lateral (or posterior) wall involvement. The paper may be thought of as a story with a major plot and a subplot. The major plot makes the case, quite eloquently, that the newer imaging techniques such as contrast-enhanced MRI can and should be used to examine criteria used to diagnose various cardiac abnormalities such as infarction and to serve as the basis for modifications in criteria and terminology. The subplot concerns the requirements that should be satisfied before changing existing terminology and criteria from that which is well established and familiar to that which is not. The paper convincingly makes the argument that current ECG criteria for the diagnosis of myocardial infarction may require upgrading and perhaps significant change. However, it does not deal with the issue of whether specific requirements should be met to recommend or accept such changes. The study involves 45 patients having infarctions in clearly defined regions labeled lateral, inferior, and inferolateral that are thought to be in the distribution of the right and left circumflex coronary arteries. This number includes 15 patients with an infarction in the region termed inferior. Their ECGs are typical for the pattern more classically defined as “inferior.” There are 9 patients with infarctions in the region termed lateral, and their ECGs, with the modifications previously described, are consistent with those more typically referred to as “posterior.” The remaining 21 patients have infarctions in both regions, and their ECGs are quite consistent with those more typically referred to as “inferoposterior.” The question can then be raised as to whether these results are adequate to recommend that existing ECG criteria for infarctions in the defined regions be changed. The statistical analysis of the data does indeed support this recommendation. The second question is whether enough evidence exists to warrant a change in terminology from “posterior” and “inferoposterior” to “lateral” and “inferolateral.”