This patient presents with chest pressure at rest and an anterior ST segment elevation myocardial infraction (STEMI) seen on 12-lead EKG. This patient should be given aspirin, IV fluids to increase the preload status, and receive immediate coronary reperfusion therapy. This patient’s hypotension is likely due to infarction of the left ventricle causing poor cardiac output (Choice D). This is known as cardiogenic shock. The patient has been vomiting, but the acute onset of symptoms and STEMI on EKG make poor cardiac output (Choice D) more likely than hypovolemia (Choice A) as the cause for the patient’s condition. Systemic infection (Choice B) and pulmonary embolism (Choice C) are also less likely given the clinical information in the case and the STEMI on EKG. The best answer is Choice D. Please see the chart below for further detailing of the different types of shock.
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.
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)
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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 2, 2022