The STEMI Equivalents
It is 2:00am and you are at the bedside of your patient who is having active chest pain. You pull the EKG off the machine before the tech has time to hand it to your attending. What’s one of the first things you look for? STEMI of course. Why? Because time is myocardium. But not all STEMI’s present as tombstones. So, let’s review so that we are ready.
First, let’s start with the most basic definitions.
Properly identifying ST elevation can be tricky with early re-polarization and wandering baselines. If in doubt, try this.
Identify the baseline with the t to p segment.
Find the j point associated with that p and go one small box to the right of that j point. This, my friend, is the ST segment point that we care about.
Now count the boxes up or down between the baseline (the t to p segment) and the ST segment point (one small box to the right of the j point).
Follow this technique and you are sure to impress your cardiology colleagues.
Check modified Sgarbossa criteria.
- Concordance + 1mm elevation in any lead
- Concordance + 1mm depression in V1-V3
- Discordance + elevation that is at least 25% of the S wave depth
Okay, now you have convinced yourself that your patient does not meet STEMI criteria based on the above definitions…but something still doesn’t look right. What else would make you send this patient to the cath lab? Cue the STEMI equivalents.
Why do we care? Because time is myocardium and these patient’s need to go to the cath lab immediately.
Focus your attention on the precordial leads. There are three main equivalents to be on the look out for.
- 1 -
From the depths of icebergs up to the cold winter mountain tops, de Winter T waves are suggestive of a complete LAD occlusion. CODE STEMI. Activate that cath lab.
- 2 -
When you see tall T waves with a broad base, be concerned. This may be an early anterior STEMI. Again, CODE STEMI. Activate the cath lab. Be warned…these scary T waves may be transient so do not feel reassured if they disappear on serial EKGs.
- 3 -
Does that ST look depressed in V1-V3…even just a little? Don’t just flip the EKG over. Get a posterior EKG. Your tech doesn’t know how? Have no fear. You do now.
Take leads V4-V6 and move them posteriorly. They are now V7-V9. Place them in a straight horizontal line with V7 at the posterior axillary line, V8 just below the tip of the scapula, and V9 just left of the vertebrae.
Now repeat the EKG.
Cross out V4-V6 and label it V7-V9.
Now, do you see 0.5mm ST elevation in any one lead in V7-V9? If so, activate the cath lab. You, our incredible rockstar, have just identified a posterior STEMI.
We have just completed our review of STEMI equivalents, but before we end, we think it is important to touch on one more pattern that is not technically an equivalent but is a blaring warning sign with flashing bright lights telling you that a STEMI is on its way…and not just any STEMI…but a proximal LAD occlusion. These are called Wellen’s Waves. Like the equivalents, they are seen in the precordial leads. Call cardiology and for the love of all things emergency medicine DO NOT STRESS TEST. They may not be going emergently to the cath lab, but it is likely in their very near future.
Okay team. Good review. Send us a message with questions, comments, or other tips.
Thank you to our references!
Burns, E., Burns, E. B., & Prehospital & Retrieval Medicine. (2017, November 15). The ST segment - Life in the Fast Lane ECG Library. Retrieved from https://lifeinthefastlane.com/ecg-library/st-segment/
Cadogen, M (2018, November25). Sgarbossa criteria - Life in the Fast Lane ECG Library. Retrieved from https://litfl.com/sgarbossa-criteria-ecg-library/
Genzlinger MA, Eberhardt M. Analyzing prominent T waves and ST-segment abnormalities in acute myocardial infarction. J Emerg Med. 2012;43(2):e81-85.
Hollander JE, Diercks DB. Acute Coronary Syndromes. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e New York, NY: McGraw-Hill; 2016. http://accessmedicine.mhmedical.com.liboff.ohsu.edu/content.aspx?bookid=1658§ionid=109449629. Accessed September 14, 2018.
Lawner BJ, Nable JV, Mattu A. Novel patterns of ischemia and STEMI equivalents. Cardiol Clin. 2012;30(4):591-599.
Signed: Jesse Lee, MD and Carly Dougher, MD
Co-signed: Edward Lew, MD