Written by Carmen Wolfe
When ST elevation is present in the anterior precordial leads, a validated 4-variable formula can help differentiate LAD coronary occlusion from benign early repolarization.
Why does this matter?
ST elevation in the anterior precordial leads can be tricky. In some cases, it represents acute myocardial infarction, and in other cases it represents a benign finding. This distinction will drastically change the patient’s plan of care, so we must be sure we can spot the difference. While abnormal R wave progression or abnormal ST segment morphology may provide some subtle clues for acute ischemia, wouldn’t it be great if there were a validated method for determining the difference?
Bad news or benign finding?
This Annals clinical case features an ECG with ST segment elevation in the anterior precordial leads, similar to the open access example below (from Dr. Smith’s ECG blog, licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, ECG not modified). While the Annals ECG doesn’t meet STEMI criteria for cath lab activation, it does have subtle changes to suggest occlusion myocardial infarction of the LAD as opposed to benign early repolarization. R-wave regression and a straight ST segment morphology provide convincing clues in the Annals article. The ECG below has minimal ST elevation in V1-V4. Is there another way to be more sure this subtle anterior ST elevation is truly concerning before you call cardiology?
A validated formula exists to help with this differentiation, and while it’s not something that can be easily memorized, it can be readily found and utilized through online resources like MDCalc. You’ll need to calculate the QTcB, QRS amplitude in V2, R wave amplitude in V4, and the ST segment elevation 60ms after the J point in V3, and input these numbers into the formula. The calculator does the hard work and provides a number that predicts with high sensitivity and specificity whether or not you have an occlusion myocardial infarction. I encourage you to try this out next time you’re on the fence about an ECG with some anterior precordial ST segment elevation of unclear significance. In fact, click the MDCalc link and try it on the ECG above. What does the 4-variable calculator show with this tracing: likely benign early repolarization or likely anterior STEMI? If you have the chance to read this one in full text, the ECG examples are worth a look.
Ann Emerg Med. 2021 Jun;77(6):593-596. doi: 10.1016/j.annemergmed.2020.09.443.