STEMI Limitations

STEMI Limitations

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.

Prominent T wave with upsloping ST depression in precordial leads
Prominent T wave with upsloping ST depression in precordial leads. https://litfl.com/de-winter-t-wave-ecg-library/

Wellen's Syndrome: Severe proximal LAD stenosis.

Biphasic or deep inverted T waves in V2 V3
Biphasic or deep inverted T waves in V2 V3 https://litfl.com/wellens-syndrome-ecg-library/

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

Infero-lateral STEMI with ST depression in V1 to V4 suggesting posterior MI
Infero-lateral STEMI with ST depression in V1 to V4 suggesting posterior MI https://litfl.com/posterior-myocardial-infarction-ecg-library/
Same patient with posterior EKG showing ST elevation in posterior leads
Same patient with posterior EKG showing ST elevation in posterior leads https://litfl.com/posterior-myocardial-infarction-ecg-library/

Right Ventricular MI: Complicates inferior STEMI, RCA occlusion

ST elevation in V1, ST elevation in III more than II
ST elevation in V1, ST elevation in III more than II https://litfl.com/right-ventricular-infarction-ecg-library/

ST elevation in aVR with diffuse ST depression: Left Main Coronary Artery (LMCA), proximal LAD, or triple vessel occlusion

ST elevation in aVR with diffusion ST depression
ST elevation in aVR with diffusion ST depression https://litfl.com/st-elevation-in-avr/

ST depression and T-wave inversion in aVL: RCA, LCx, or LAD occlusion

Reciprocal ST depression in avL
Reciprocal ST depression in avL https://litfl.com/inferior-stemi-ecg-library/

Hyperacute T-waves: LCx occlusion

Broad asymmetrical T wave
Broad asymmetrical T wave https://litfl.com/t-wave-ecg-library/

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.
Cite this article as: Israa M Salih, UAE, "STEMI Limitations," in International Emergency Medicine Education Project, May 31, 2021, https://iem-student.org/2021/05/31/stemi-limitations/, date accessed: July 3, 2022

Recent Blog Posts By Israa Salih

A case of decreasing resistance in ER

a case decreasing resistance in er

I keep games on the 4th home screen of my cell phone. The third screen is blank. A minuscule of energy required to swipe my thumb has prevented me one too many times from mindlessly launching an RPG. Only to realize 2 hours later I had other plans for those 2 hours. An American comedian, the late Mitch Hedberg famously joked once,

Mitch Hedberg (1968-2005)
Mitch Hedberg (1968-2005)

I have always believed that the subtle truths kneaded so artfully in seemingly light, small-talk-worthy jokes are what makes a comedian a genius. How many times have you thought that you need to pick up that particular grocery or fill up that one conference form only to instead get consumed by what was easily available?

Our mind is built so that it follows the path of least resistance no matter how insignificant the resistance is. Although smudged all over the canvas of self-help, non-fiction genre, medicine somehow isn’t used frequently to exemplify the path of least resistance.

Today, I present to you a case that inspired us at Beltar, to remove one such small resistance from our workflow. The implications as you will see were no less than life-saving.

Rural Health System : Oversimplified

Before I present to you the case, a small preamble: Health care in rural Nepal is still run mostly by paramedics. No matter what spectrum you fall in terms of appreciating their work, the fact remains that they are the major workforce we have at the rural. It suffices to say that they are the portal of entry to the health system of our country for many. All emergency cases, once screened and declared complicated, the medical officer (usually a MBBS doctor) at the PHC sees the patient. Majority of cases are seen only by paramedics – considering 3 to 5 paramedics, usually and barely one medical officer in most PHCs.

A mobile game I wouldn't play

Now that the characters are in place, let’s dive right into the no less than a fairy tale land of the rural health system. Lamenting about the obvious lack of resources has been so old school that I don’t even make a typo while typing about it these days. We had one ECG machine at Beltar. The old ECG machine with its squeaky sound and myriad varieties of artifacts stood with all its mighty bulk inside a locked door of a room. The key protected from no one in particular by the office assistant who would open the door, drag the machine out, bring it to the bedside. The paramedic who decided to do the ECG would then untangle the wire glazed with what little of gel we had applied to the previous patient. He would then connect the limb leads and the pre-cordial leads with the trusty suction knobs which hopefully has some gel left from the previous use and then comes the biggest connection to be made: connecting the machine to the power grid. “Don’t you keep your machine charged!?”, you ask. We do. But the Li-ion battery probably has undergone autophagy, or whatever fancy name the process is given. That is a lot of steps and by extension, a lot of resistance. If this were a mobile game, I don’t think I would be addicted to it.

A Race Against Time

A patient with diabetes who had visited our ER a couple of times before was being monitored for chest pain at around 7 AM on a Saturday morning. I was washing my clothes on the first floor unaware that my Saturday is not going to be about laundry and daily chores. When I was called to check the patient, she was already deteriorating at a rate far greater than our PHC could ever catch up. We tried to borrow the speed of an ambulance and refer the patient to a higher center. An ST elevation in any two contiguous lead is an MI. Our paramedics knew that. To everybody’s surprise, ECG was not done! Given the fact that we did not have cardiac enzymes available at the PHC and Aspirin was all we could have prescribed before discharge anyway: we gave the patient 2 Aspirin tablets to chew and referred her as fast as we could. My paramedic colleagues have demonstrated utmost clinical competence and professionalism too many times to doubt any of that. The work environment was still error-prone and the circumstance demanded a change. Could we have changed the outcome given the same resources and clinical scenario? Maybe we need to decrease the resistance I thought. Changing how we store ECG (shown in the picture below), making it more accessible not only increased the frequency with which it was being used but also served as a reminder. A physical question hanging down the IV stand asking anyone who is attending a case, “Do you need to use me?”

ECG machine in plain sight with IV stand holding the limb and pre-cordial leads for accessibility

Workarounds: Because Solutions are Late to the Party.

If you have been following my writings, you’d have noticed this as another small tweak, a workaround, a nudge to the existing system so to speak that isn’t the substitute for the actual sustainable solution. Robust training that helps hard-working paramedics conceptualize and understand the protocols related to the use of basic yet life-saving diagnostics like ECG can be a start. We tried printing and pasting some protocols on the walls; another workaround we hope would help make patient care better until it actually sustainably improves. Another workaround that a friend suggested was: everyone who aches above the waist, gets an ECG. Such simplification works well to decrease the resistance in learning complex protocols. I am sure there are plenty of workarounds used worldwide, a necessity, after all, is the mother of invention. I leave you with a thought: What effect do you think will a systematic sharing of such workarounds among the rural healthcare workers will produce?

Guides to ECG electrode placement and protocols
Cite this article as: Carmina Shrestha, Nepal, "A case of decreasing resistance in ER," in International Emergency Medicine Education Project, February 21, 2020, https://iem-student.org/2020/02/21/a-case-of-decreasing-resistance-in-er/, date accessed: July 3, 2022

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