The Case:
45-year-old Spanish speaking male with no known past medical history presented to the ED with 2-3 hours of severe back pain and throat pain. The pain started at rest with no specific aggravating or alleviating factors. The patient reported having similar intermittent episodes in the past, but this occurrence was more severe and persistent. Associated symptoms included nausea without emesis. He appeared uncomfortable and slightly diaphoretic. His initial SBP was >180 and other vitals were within normal limits. His exam was otherwise unremarkable with clear breath sounds and equal pulses.
Initial EKG Interpretation:
Normal sinus rhythm, left axis deviation, normal intervals, q wave in lead III and aVF, R wave in V3 which was less than V2, ST segment depression in leads 1, aVL, V2, V3, and nonspecific T wave changes.
What does this EKG suggest?
His EKG suggested a posterior MI as well as other signs of ischemia. Posterior MI is suggested by large R waves (>30ms) in V2 and V3. The R/S ratio in V2 is nearly >1 and the R wave in V3 was smaller than V2. V2 and V3 had significant horizontal ST depressions. There is also suggestion of reciprocal changes with ST depressions in I and aVL >0.5mm. In addition, there were hyperacute T waves in III, and aVF.
The q wave in lead III could be normal variant but the q wave in aVF was greater than 2mm.
Management:
Although the patient did not meet criteria for traditional cath lab activation, he had an initial EKG concerning for a posterior MI and possible infero-lateral involvement. A posterior EKG was immediately obtained showing very mild ST elevation in V7 and V8. For reference, in men and women at any age >0.05mm in leads V7-V9 is considered a STEMI. Unfortunately, this EKG was not recorded in the EMR.
A code STEMI was activated, and the patient was given sublingual nitroglycerin and morphine for his pain.
Given the patient presented with marked hypertension and severe back pain without chest pain, he underwent an emergent CT Angiography to rule out dissection, which was unremarkable. The patient was then given aspirin. A bedside echo was also performed by the ED providers demonstrating posterolateral hypokinesis, no effusion, and preserved ejection fraction. Cardiology was consulted and they recommended pain control, serial serum troponin levels and EKGs. The initial troponin was mildly elevated at 0.06 and eventually doubled to .112. Repeat EKGs continued to show ST depression in V2, as well as a new q wave in lead II, and deeper, wider q waves in lead III and aVF. Throughout his stay in the ED, the patient required more opioids and sublingual nitroglycerin to control his pain.
Ultimately the patient was taken to the cath lab which showed severe disease of the distal left main, mid left circumflex ostial OM1, distal D2, and distal RCA. Due to his severe disease, the patient was taken to the OR with CT surgery for an emergent CABG. There was 100% occlusion of the 1st obtuse marginal artery, a branch of the LCA which was felt to be the culprit for the patient’s presentation. The LCA is often involved in posterior MI, particularly in isolated posterior MI. Posterior MI is defined as infarction of the left ventricle underneath the atrioventricular sulcus. On electrocardiogram, it is defined as ST segment depression in leads V1-V3 accompanied by tall broad R waves, upright T waves, and a dominant R wave in in V2. Posterior infarction typically associated with 15-20% of acute STEMIs in particular with inferior or lateral infarctions. Isolated posterior MIs occur 3-11% of the time.
Unfortunately, there is no direct way on the standard 12-lead EKG to observe ST elevation for PMI which is why they are often missed. This case highlights how atypical OMI, in particular posterior OMI, can lead to delayed diagnosis and catheterization.
2nd EKG:
Figure 2: Repeat EKG
US:
Figure 3: Echocardiogram image
Authored by Alejandro Negrete, MD
References:
Van Gorselen EO, Verheugt FW, Meursing BT, Oude Ophuis AJ. Posterior myocardial infarction: the dark side of the moon. Neth Heart J. 2007 Jan;15(1):16-21. PMID: 17612703; PMCID: PMC1847720.
Fourth Universal Definition of Myocardial Infarction (2018). Kristian Thygesen, Joseph S. Alpert, Allan S. Jaffe, Bernard R. Chaitman, Jeroen J. Bax, David A. Morrow, Harvey D. White, The Executive Group on behalf of the Joint European Society of Cardiology (ESC)/American College of Cardiology (ACC)/American Heart Association (AHA)/World Heart Federation (WHF) Task Force for the Universal Definition of Myocardial Infarction.
Alsagaff, M.Y., Amalia, R., Dharmadjati, B.B. et al. Isolated posterior ST-elevation myocardial infarction: the necessity of routine 15-lead electrocardiography: a case series. J Med Case Reports 16, 321 (2022). https://doi.org/10.1186/s13256-022-03570-w
Lowenstein, S. (2018). Posterior Wall Myocardial Infarction. In Critical Cases in Electrocardiography: An Annotated Atlas of Don't-Miss ECGs for Emergency Medicine and Critical Care (pp. 143-159). Cambridge: Cambridge University Press.