In this ECG Cases blog we look at 9 patients with potential ischemic symptoms and discuss the limits of STEMI criteria as well as the evidence driving the Occlusion MI paradigm shift.

Written by Jesse McLaren; Peer Reviewed and edited by Anton Helman, June, 2024

9 patients presented with potentially ischemic symptoms. Which had Occlusion MI?

Case 1. 35 year old with shortness of breath on exertion

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Case 2: 60 year old with two days of chest pain

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Case 3: 60 year old, previously healthy, with 5 hours of chest pain

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Case 4: 50 year old with epigastric pain

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Case 5: 50 year old with hours of chest pain

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Case 6: 60 year old with chest pain

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Case 7: 70yo with chest pain

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Case 8: 60yo with refractory chest pain and runs of VT

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Case 9: 65 year old with exertional chest pain now resolved

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STEMI vs Occlusion MI

Defining a pathology by one part of one test, dichotomized by milimeter criteria, produces frequent false positive STEMI (i.e STEMI criteria on ECG in a patient without acute coronary occlusion), leading to unnecessary cath lab activation. But a more dangerous limitation is false negative STEMI (i.e. no STEMI criteria on ECG, but the patient has an acute coronary occlusion), leading to delayed reperfusion. A quarter of “non-STEMI” patients have a totally occluded artery, with delayed reperfusion and higher mortality.[1] As the new ACC expert consensus on chest pain the ED warned, STEMI criteria “will miss a significant minority of patients with acute coronary occlusion.”[2] But in the STEMI paradigm there’s no such thing as false negatives, because these patients are by definition “non-STEMI”. As a result, discharge diagnoses change to highlight false positives, but not false negatives – which prevents providers from learning about missed occlusions.[3]

Evidence-based ECG interpretation, correlated with angiographic outcome, has identified many ways to identify both false positive and false negative STEMI.[4] These advances have led to a proposed paradigm shift from STEMI to Occlusion MI (OMI): rather than dichotomizing acute myocardial infarction by presence or absence of ST elevation milimeter criteria on the ECG, it should be based on whether the patient has an OMI requiring emergent reperfusion.[5] OMI signs look at the ECG in totality (including acute Q waves, ST segment morphology, hyperacute T waves, reciprocal change), in proportionality (interpreting ST/T changes relative to the preceding QRS), and recognize the dynamic nature of occlusion MI which can spontaneously reperfuse (with reperfusion T wave inversion) and reocclude (pseudonormalization). OMI ECG signs have twice the sensitivity of STEMI criteria, with preserved specificity [6], and are being incorporated into expert-trained artificial intelligence. [7]

Occlusion MI is both an ECG diagnosis AND and a clinical one

But diagnosis of OMI is not restricted to the ECG: it is a clinical diagnosis that incorporates advanced ECG interpretation, complementary POCUS[8] and emergent reperfusion for refractory ischemia regardless of the ECG. This creates the possibility of a new generation of ED quality improvement [9]. Inspired by the OMI paradigm shift, this blog developed from a quality improvement project to learn and share ECG interpretation for OMI to reduce reperfusion delays [10]. Because learning about OMI requires interpretation the ECG in totality and with consideration to proportionality, learning OMI also helps with ECG interpretation in general. This blog has included dozens of posts looking at specific ECG features of OMI and a post on ECG + POCUS, and for this 50th post is looking at the paradigm shift from STEMI to OMI.

Back to the cases

Case 1. 35 year old with shortness of breath on exertion. False positive STEMI

  • Heart rate/rhythm: sinus bradycardia
  • Electrical conduction: normal intervals
  • Axis: normal axis
  • R-wave progression: normal
  • Tall/small voltages: large voltages, large R waves in apical distribution
  • ST/T changes: secondary, discordant and proportional ST/T changes

= apical hypertrophic cardiomyopathy confirmed on echo, false positive STEMI

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Case 2: 60 year old with two days of chest pain. False positive STEMI

  • H: normal sinus
  • E: first degree AV block
  • A: borderline left axis
  • R: normal R wave progression
  • T: normal voltages
  • S: STE I/aVL prominent J waves, mild STE and no hyperacute T waves, inferior TWI

= early repolarization, false positive STEMI. Cath lab activated: normal coronaries and troponins

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Case 3: 60 year old, previously healthy, with 5 hours of chest pain. STEMI(-)OMI

  • H: normal sinus
  • E: normal conduction
  • A: normal axis
  • R: loss of anterior R waves
  • T: normal voltages
  • S: deWinter T wave in V3 and hyperacute T in V4, with straining of ST in I and biphasic V in aVL

=STEMI(-)OMI proximal LAD occlusion, initially missed. An hour later repeat ECG showed subtle STE laterally

Cath lab activated: 99% first diagonal occlusion, first troponin 5,000 and peak 65,000ng/L. Discharged ECG showed anterolateral Q waves and reperfusion T wave inversion:

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Case 4: 50 year old with epigastric pain. False positive STEMI

  • H: normal sinus
  • E: normal conduction
  • A: borderline right axis
  • R: normal R wave progression
  • T: normal voltages
  • S: mild inferior STE but no hyperacute T waves and no reciprocal STD-TWI in aVL

=false positive STEMI. Unecessary cath lab activation. Troponins negative and diagnosed as pancreatitis

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Case 5: 50 year old with hours of chest pain. STEMI(+)OMI

  • H: normal sinus
  • E: normal conduction
  • A: normal axis
  • R: early R wave progression with tall R in V2
  • T: normal voltages
  • S: inferior Q + STE + hyperacute T waves, with reciprocal STD/TWI in I/aVL and STD V2-3

=infero-posterior Occlusion MI. Cath lab activated: 100% RCA occlusion. First trop 90,000 and peak 300,000ng/L. Discharge ECG showed infero-posterior Q waves and reperfusion T wave inversion:

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Case 6: 60 year old with chest pain. STEMI(-)OMI

  • H: normal sinus
  • E: normal conduction
  • A: physiologic left axis
  • R: normal R wave
  • T: LVH in aVL
  • S: primary STD V3-4, with false negative posterior leads

=posterior STEMI(-)OMI. Cath lab activated: 99% circumflex occlusion, peak trop 22,000ng/L. Discharge diagnosis ‘STEMI’ because of cath lab activation, but no ECG met STEMI criteria.

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Case 7: 70yo with chest pain. STEMI(-)OMI

  • E: RBBB morphology
  • A: left axis
  • R: early R wave
  • T: normal voltages
  • S: discordant ST changes but excessive in III with STE/S >25%

=inferior STEMI(-)Occlusion MI. Cath lab activated: 100% RCA occlusion. Follow up ECGs showed resolution of disproportionate STE:

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Case 8: 60yo with refractory chest pain and runs of VT. STEMI(-)OMI

  • H: sinus rhythm
  • E: normal conduction
  • A: normal axis
  • R: normal R wave
  • T: normal voltages
  • S: inferior Q waves, lateral TWI

= nondiagnostic ECG. If the patient had presented with a resolved episode of chest pain and positive troponin, this ECG could be consistent with non-occlusive MI (NOMI). But the patient presented with refractory chest pain and electrical instability = clinical OMI. Door to cath lab time 6 hours. Triple vessel disease with 100% circumflex occlusion, peak trop 70,000ng/L. No ECG evolution. Discharge diagnosis: ‘NSTEMI’

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Case 9: 65 year old with exertional chest pain now resolved. STEMI(-)OMI with spontaneous reperfusion, at risk for reocclusion

  • H: normal sinus
  • E: normal conduction
  • A: normal axis
  • R: normal R wave
  • T: normal voltages
  • S: primary biphasic T waves V2-3

= resolved chest pain with preserved R waves and primary biphasic T waves in LAD distribution = Wellens syndrome = brief LAD occlusion with spontaneous reperfusion, at risk for reocclusion. First trop 2 and repeat 60. Admitted as non-STEMI

Next day ECG showed evolution of reperfusion T wave inversion with deeper symmetric T wave inversion (from “Wellens A” to “Wellens B”), evolution:

While waiting for angiogram had recurring chest pain:

ST segments and T waves are up again, from spontaneous reoccluson. Cath lab activated: LAD occlusion. Discharge diagnosis ‘NSTEMI’

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Take home points on STEMI vs Occlusion MI

  1. If there is STEMI criteria, consider false positives eg. secondary and proportional to LVH or BER
  2. If there is no STEMI criteria, consider false negatives and look for other signs of occlusion, eg. acute Q waves or loss of R waves, hyperacute T waves, or reciprocal STD/TWI
  3. If the ECG is nondiagnostic, consider other OMI signs including clinical (refractory ischemia, hemodynamic/electrical instability) and POCUS (new regional wall motion abnormalities)

* For interactive online and live ECG interpretation courses for medical students, residents, paramedics, and emergency physicians (focusing on STEMI vs OMI), visit heartsECGcourse.com

References

  1. Khan AR, Golwala H, Tripathi A, et al. Impact of total occlusion of culprit artery in acute non-ST elevation myocardial infarction: a systematic review and meta-analysis. Eur Heart J 2017 Nov 1;38(41):3082-3089
  2. Kontos MC, de Lemos JA, Deitelzweig SB, et al. 2022 ACC expert consensus decision pathway on the evaluation and disposition of acute chest pain in the emergency department: a report of the American College of Cardiology solution set oversight committee. J Am Coll Cardiol 2022 Nov 15;80(20):1925-1960
  3. McLaren JTT, El-Baba M, Sivashanmugathas V, et al. Missing occlusions: quality gaps for ED patints with occlusion MI. Am J Emerg Med 2023 Nov;73:47-54
  4. Miranda DF, Lobo AS, Walsh B, et al. New insights into the use of the 12-lead electrocardiogram for diagnosing acute myocardial infarction in the emergency department. Can J Cardiol 2018 Feb;34(2):132-145
  5. Meyers HP, Bracey A, Lee D, et al. Comparison of the ST-elevation myocardial infarction (STEMI) vs NSTEMI and Occlusion MI (OMI) vs NOMI paradigms of acute MI. J Emerg Med 2021 Mar;60(3):273-284
  6. Meyers HP, Bracey A, Lee D, et al. Accuracy of OMI ECG findings versus STEMI criteria for diagnosis of acute coronary occlusion myocardial infarction. IJC Heart and Vasc 2021 Apr;33: 100767
  7. Herman R, Meyers HP, Smith SW, et al. International evaluation of an artificial-intelligence-powered electrocardiogram model detecting acute coronary occlusion myocardial infarction. Eur Heart J Digital Health 2024 Mar;5(2): 123-133
  8. Bracey A, Massey L, Pellet AC, et al. FOCUS may detect wall motion abnormalities in patients with ACS. Am J Emerg Med 2023 Jul;69:17-22
  9. McLaren JTT, Meyers HP, Smith SW, et al. From STEMI to occlusion MI: paradigm shift and ED quality improvement. CJEM 2022;24:250-255
  10. McLaren JTT, Taher AK, Kapoor M, et al. Sharing and Teachingn Electrocardiograms to Minimize Infarction (STEMI): reducing diagnostic time for acute coronary occlusion in the emergency department. Am J Emerg Med 2021 Oct;48:18-32