A Simplified Formula Discriminating Subtle Anterior Wall Myocardial Infarction from Normal Variant ST-Segment Elevation

Abstract

Benign variant (BV) ST-segment elevation (STE) is present in anterior chest leads in most individuals and may cause diagnostic confusion in patients presenting with chest pain. Recently, 2 regression formulas were proposed for differentiation of BV-STE from anterior ST-elevation myocardial infarction (MI) on the electrocardiogram, computation of which is heavily device-dependent. We hypothesized that a simpler visual-assessment-based formula, namely (R-wave amplitude in lead V4 + QRS amplitude in V2) - (QT interval in millimeters + STE60 in V3), will be noninferior to these formulas. Consecutive cases of proven left anterior descending occlusion were reviewed, and those with obvious ST elevation MI were excluded. First 200 consecutive patients with noncardiac chest pain and BV-STE were also enrolled as a control group. Relevant electrocardiographic parameters were measured. There were 138 anterior MI and 196 BV-STE cases. Our simple formula was superior to the 3- and noninferior to the 4-variable formulas. This new practical formula had an excellent area-under curve of 0.963 (95% confidence interval, 0.946 to 0.980, p<0.001). It also had a sensitivity, specificity and diagnostic accuracy of 86.9%, 92.3%, and 90.1%, respectively. In conclusion, a simple visual assessment-based formula can reliably differentiate STE MI from BV-STE. Also, our results emphasize that focusing only on STE for diagnosing acute coronary occlusion is extremely insensitive and even puts the term "STEMI" itself into question.