In 2000, the ST-Elevation Myocardial Infarction (STEMI) paradigm revolutionized the management of Acute Coronary Syndrome (ACS), substituting the previous dichotomy between Q-wave versus non-Q wave myocardial infarcts (MI). Subcategorizing aimed to predict completely occluded arteries and the need for immediate intervention, namely, emergent cardiac catheterization to open an occluded coronary artery in STEMI. However, literature has shown that STEMI and occlusion myocardial infarction (OMI) are not interchangeable, with clear evidence of benefit from early reperfusion in both entities. Moreover, definitions STEMI and Non-ST-elevation myocardial (NSTEMI) can miss a large proportion of acute coronary occlusions; STEMI as a category can miss 30% of occlusion MI up to 50% in left circumflex, and NSTEMI was only associated with total MI in a quarter of cases.
As any Emergentologist at any level can relate, it was only recently when my ED held a morbidity and mortality meeting for a presumably delayed cath lab activation. The patient had all the risk factors, a typical chest pain which resolved in the ED, normal vitals and an ECG that didn’t meet the STEMI criteria; however, when he went for urgent angiography, the LAD was totally occluded.
A new paradigm: OMI vs. NOMI
The OMI manifesto, introduced by Dr Stephen Smith, Dr Pendell Myers, and Dr Scott Weingart might provide a better solution in the management of ACS. The fundamental question is: Does the patient have an acute coronary occlusion that would benefit from immediate intervention? Based on this question, the following diagram was suggested to substitute STEMI versus NSTEMI paradigm. The manifesto also contains rules to diagnose acute MI in certain categories of patients, such as patients with left bundle branch block (LBBB), left ventricular paced rhythm, terminal QRS distortion, normal ST-elevation vs. left anterior descending artery (LAD) occlusion, anterior ventricular aneurysm vs. acute MI, ST depression in aVL.
Basic concepts
ACS is a spectrum of clinical presentations divided into STEMI, NSTEMI and unstable angina, based on ECG findings and cardiac markers. The American Heart Association/American College of Cardiology (AHA/ACC) and European Society of Cardiology (ESC) define STEMI as new ST elevation at the J point in the absence of LV hypertrophy or LBBB in at least 2 contiguous leads. The elevation must be at least 2 mm (0.2 mV) in men or 1.5 mm (0.15 mV) in women in leads V2–V3 and/or 1 mm (0.1 mV) in other contiguous chest leads or the limb leads.
AHA/ACC recommends primary percutaneous coronary intervention (PCI) for patients with STEMI and ischemic symptoms of less than 12 hours’ duration. In NSTEMI, the recommendation is to perform urgent/immediate angiography with revascularization if appropriate in patients who have refractory angina or hemodynamic or electrical instability.
A meta-analysis of 46 trials with a total of 37 757 patients, including data from the International Study of Comparative Health Effectiveness with Medical and Invasive Approaches (ISCHEMIA) and Complete versus Culprit-Only Revascularization Strategies to Treat Multi-vessel Disease after Early PCI for STEMI (COMPLETE) trials demonstrated that PCI prevents death, cardiac death, and MI in patients with unstable coronary artery disease (CAD). The study defined unstable CAD as post-MI patients who haven’t received reperfusion therapy, multi-vessel disease following STEMI, non–ST-segment–elevation acute coronary syndrome.
STEMI Equivalents
For patients with persistent chest pain, hemodynamic instability and certain patterns of EKGs, it’s advisable to consider immediate/urgent PCI. The following patterns were found consistent with total occlusion or critical ischemia of the coronaries so every Emergentologist should familiarize her/himself with those: (All displayed ECGs are from Life in the Fast Lane ECG library)
De Winter T-wave: LAD occlusion.
Wellen's Syndrome: Severe proximal LAD stenosis.
LBBB with positive Sgarbossa criteria
New LBBB without meeting Sgarbossa criteria is not considered an indication for cath lab activation any longer. Smith modified Sgarbossa criteria are:
- Concordant ST elevation ≥ 1 mm in ≥ 1 lead
- Concordant ST depression ≥ 1 mm in ≥ 1 lead of V1-V3
- Proportionally excessive discordant STE in ≥ 1 lead anywhere with ≥ 1 mm STE, as defined by ≥ 25% of the depth of the preceding S-wave
Positive Sgarbossa criteria in ventricular paced rhythm
Posterior MI: Left Circumflex (LCx) Artery or right coronary artery (RCA) occlusion
Right Ventricular MI: Complicates inferior STEMI, RCA occlusion
ST elevation in aVR with diffuse ST depression: Left Main Coronary Artery (LMCA), proximal LAD, or triple vessel occlusion
ST depression and T-wave inversion in aVL: RCA, LCx, or LAD occlusion
Hyperacute T-waves: LCx occlusion
References and Further Reading
- Amsterdam, E. A., Wenger, N. K., Brindis, R. G., Casey, D. E., Ganiats, T. G., Holmes, D. R., … & Zieman, S. J. (2014). 2014 AHA/ACC guideline for the management of patients with non–ST-elevation acute coronary syndromes. Journal of the American College of Cardiology, 64(24), e139-e228.
- Chacko, L., P. Howard, J., Rajkumar, C., Nowbar, A. N., Kane, C., Mahdi, D., … & Ahmad, Y. (2020). Effects of percutaneous coronary intervention on death and myocardial infarction stratified by stable and unstable coronary artery disease: a meta-analysis of randomized controlled trials. Circulation: Cardiovascular Quality and Outcomes, 13(2), e006363.
- Coven, D. L. (2020). Acute Coronary Syndrome. Retrieved April 9, 2021, from https://emedicine.medscape.com/article/1910735-overview
- Khan, A. R., Golwala, H., Tripathi, A., Bin Abdulhak, A. A., Bavishi, C., Riaz, H., … & Bhatt, D. L. (2017). Impact of total occlusion of culprit artery in acute non-ST elevation myocardial infarction: a systematic review and meta-analysis. European heart journal, 38(41), 3082-3089.
- Kreider, D., Berberian, J. (2019). STEMI Equivalents: Can’t-Miss Patterns. EMResident. Retrieved April 9, 2021, from https://www.emra.org/emresident/article/stemi-equivalents/
- Life in the Fast Lane. (n.d.). ECG Library. Retrieved April 9, 2021, from https://litfl.com/ecg-library/
- Meyers, P. (2018). Guest Post – Down with STEMI – The OMI Manifesto by Pendell Meyers. EM Crit RACC. Retrieved April 9, 2021, from https://emcrit.org/emcrit/omi-manifesto/
- O’gara, P. T., Kushner, F. G., Ascheim, D. D., Casey Jr, D. E., Chung, M. K., De Lemos, J. A., … & Zhao, D. X. (2013). 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction. Circulation, 127(4), 529-555.
- Wang, T. Y., Zhang, M., Fu, Y., Armstrong, P. W., Newby, L. K., Gibson, C. M., … & Roe, M. T. (2009). Incidence, distribution, and prognostic impact of occluded culprit arteries among patients with non–ST-elevation acute coronary syndromes undergoing diagnostic angiography. American heart journal, 157(4), 716-723.
