ELECTROCARDIOGRAPHIC Q-WAVE INCONSTANCY IN INFERIOR WALL MYOCARDIAL-INFARCTION

Abnormal Q waves fulfilling standard criteria are the hallmark of "Q-wave" myocardial infarction (MI).1-3 Although a surprisingly large number of enzyme-positive acute MIs do not produce Q waves,4,5 abnormal Q waves may seem to "resolve" or disappear. Disappearance of established abnormal Q waves may be explained by tissue changes during healing, scar contraction or hypertrophy of adjacent myocardium, vectorially opposite new MI reducing or canceling preexisting Q waves or recovery of stunned myocardium.6 In acute myocarditis mimicking acute MI, abnormal Q waves often disappear, presumably because of resolution of subnecrotic damage.7. In anterior wall MI, electrode placement can significantly change the QRS including Q waves, but not in inferior wall MI, diagnosed strictly from limb leads. We frequently observed Q waves with established criteria (≥0.04 second in lead aVF) to be present on one day and not on an adjacent day (Figures 1 and 2). Such inconstancy must be a confounding factor in evaluating electrocardiographic evidence. The relatively poor sensitivity of electrocardiographic criteria for inferior wall MI8 could be partly due to surprisingly frequent day to day fluctuation. © 1990.