STEMI Equivalents
Today's article is about STEMI Equivalents.
The aim of this article is to provide a basic guidance on recognizing EKG patterns in cases with coronary artery occlusion where the ST-segment elevation is not present in contiguous leads.
Patients with acute coronary occlusion (ACO) require prompt reperfusion therapy, typically through cardiac catheterization with percutaneous coronary intervention (PCI) or fibrinolysis. Traditionally, it has been taught that ACO cases exhibit ST-segment elevation (STE) in contiguous leads, categorizing them as ST-segment elevation myocardial infarction (STEMI). However, this conventional approach has led to a binary approach to emergency care: Patients with STE in contiguous leads (presumed STEMI) receive immediate reperfusion therapy, while those without STE in contiguous leads receive antiplatelet, antianginal therapy and non-emergent cardiac catheterization. The only widely accepted exception is when a posterior STEMI is suspected. This type of STEMI usually shows ST-segment depression in the right precordial leads. Therefore, if this pattern is detected, we have been instructed to use posterior leads to confirm the posterior STEMI and start acute reperfusion therapy.
For the last twenty years, studies have demonstrated that acute coronary occlusion (ACO) does not always produce the classic ST-segment elevation in contiguous leads (Koyama et al Am J Cardiol 2002). In fact, the following study has suggested that >25% of patients with ACO will not demonstrate expected ST-segment elevation (Wang, T. et al Am Heart J 2009).
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In 2022, the American College of Cardiology published the expert consensus decision pathway on the evaluation and disposition of acute chest pain in the emergency department. Most notably for our debate, the panel highlighted causes of non-ST elevation acute coronary occlusion, or what they refer to as "STEMI Equivalents".
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Let's talk about STEMI Equivalents.
The first one I want to mention is the Posterior acute MI.
Controversy exists regarding the existence of posterior myocardial infarction. It has been suggested that the electrocardiographic findings described in this entity correspond to infarction of the lateral wall (due to the oblique arrangement of the heart) and in the segmentation model, the posterior wall is replaced by the basal inferior segment (Bayes de Luna 2007 and Manuel D Cerqueira et al 2002).
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Below you can see an example of Posterior acute MI. Abnormal Q waves are also present in the inferior leads.
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Hyperacute T waves.
The panel also advised vigilance for the presence of hyperacute T waves, as these can be seen early in the presence of an acute coronary occlusion. However, they refrained from recommending immediate reperfusion therapy for these patients. Instead, they suggested conducting serial EKGs to monitor for any progression to ST-segment elevation myocardial infarction (STEMI).
Here you can see a good example of hyperacute T wave captured during a serial EKG in the setting of acute myocardial infarction due to total occlusion of the LAD.
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In the consensus, they specifically indicated for the first time that patients with left bundle branch block (LBBB) patterns or right ventricular pacemakers who manifest Sgarbossa criteria or modified Sgarbossa criteria, and patients with de Winter pattern, should undergo emergent coronary angiography.
About the Sgarbossa criteria
(read more by clicking the image)
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About de Winter pattern
(read more by clicking the image)
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The panel also listed EKG findings suggestive of acute or subacute myocardial ischemia. I will explain some of them.
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Below you can see an example of ST-segment elevation in aVR with diffuse ST-segment depression in the setting of AFIB. The angiogram showed multivessel disease and the patient was referred for CABG. Courtesy of @smithECGBlog.
About the Wellens Syndrome
(Gerson et al 1979 and De Zwaan, Wellens et al 1982)
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Below you can see an example of Wellens Syndrome, Type A. Courtesy of @walinjom.
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Below you can see an example of Wellens Syndrome, Type B. See what happened after 20 minutes. Courtesy of @DRKANZI.
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Management of patients with potential ACS.
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This consensus also marks a significant advancement in formally recognizing that many cases of acute coronary occlusion (ACO) do not exhibit typical ST-segment elevation in contiguous leads. I am optimistic that in the upcoming years, the national guidelines will start to acknowledge other equivalents of ST-segment elevation myocardial infarction (STEMI) as well.
WELL, that's it for today's article. I hope it has been useful to you. If you have a friend or colleague who has asked you about this topic, send them this article. See you at the next one.
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