Last updated 2/20/25
The traditional STEMI/NSTEMI classification of acute coronary syndrome has long been used to guide the urgency of reperfusion therapy, but emerging research suggests it may fail to identify a significant subset of patients with acute coronary occlusion (ACO) . A recent narrative review by Ricci et al. highlights high-risk ECG patterns that can indicate ACO even in the absence of classic STEMI criteria. This shift in perspective can improve early diagnosis and intervention, potentially leading to better patient outcomes. In this post, I will break down the key ECG patterns described in this paper and explain their significance.
Classic STEMI
According to the Fourth Universal Definition of Myocardial Infarction, the ST-Elevation findings suggestive of acute myocardial injury in the absence of LVH and LBBB are as follows:
New ST-elevation at the J-point in 2 contiguous leads with the cut-point…
- ≥1 mm in all leads other than leads V2–V3
- V2-V3 All Women: ≥1.5 mm
- V2-V3 Men < 40 years old: ≥2.5mm
- V2-V3 Men ≥ 40 years old: ≥2 mm
Example - Anterior STEMI with lateral extension.
Example - Inferior-Anterior STEMI
Example - Left Ventricular Hypertrophy with strain pattern/abnormal repolarization. Traditional STEMI criteria is not applicable.
Example - Left Bundle Branch Block. Traditional STEMI criteria is not applicable.
STEMI Criteria misses ACO
- de Alencar Neto et al. (2024)
- Hung et al. (2018)
- DIFOCCULT Study – Aslanger et al. (2020)
This meta-analysis found that STEMI criteria fail to detect over half of acute coronary occlusions, with a sensitivity of just 43.6% despite a high specificity of 96.5%. In contrast, the OMI-NOMI paradigm, which incorporates high-risk ECG findings such as hyperacute T waves, terminal QRS distortion, reciprocal ST depression, subtle ST elevation, and isolated posterior infarct patterns, improves sensitivity to 78.1% while maintaining a specificity of 94.4%. These findings underscore the need to move beyond STEMI-based triage to prevent missed occlusions and delays in reperfusion.
A meta-analysis of 25 studies with 60,898 NSTEMI patients found that 34% had an occluded culprit artery (OCA) at delayed angiogram, though the true number at presentation was likely higher due to spontaneous reperfusion. These patients had worse outcomes, including higher rates of cardiogenic shock (OR 1.66), reduced ejection fraction, and increased recurrent MI (OR 1.7). Despite being younger and healthier at baseline, NSTEMI patients with OCA had nearly double the 1-year mortality compared to those without occlusion. This highlights the diagnostic failure of STEMI criteria and the need for better ECG-based identification of high-risk NSTEMI cases.
The DIFOCCULT study examined 1,000 patients each from STEMI, NSTEMI, and control groups and found that 28% of NSTEMI patients were reclassified as having ACO based on blinded ECG interpretation by two cardiologists. This high-risk group had clinical profiles similar to STEMI patients, with larger infarct sizes, higher prevalence of ACO, and increased mortality. The study further demonstrated that traditional STEMI criteria miss a significant number of occlusions, whereas an ACO-based ECG approach improves early detection of patients needing urgent reperfusion therapy.
Hyperacute T waves
Recognized as a STEMI-equivalent by the American College of Cardiology (ACC), hyperacute T waves are an early ECG marker of OMI.
They are characterized by increased symmetry, increased area under the curve, and a broader, taller, less concave shape relative to the QRS complex. The T-wave to QRS ratio and total area under the curve are more reliable indicators of ACO than absolute height but unfortunately there are no validated diagnostic ECG criteria. Mimics include hyperkalemia, LVH, early repolarization, and left ventricular aneurysm. When in doubt, repeat the ECG.
Identify the hyperacute T waves in the following ECGs
ECG 1
Repeat ECG after VF arrest
Cath: LAD occlusion
ECG 2
Cath: LAD occlusion
ECG 3
ECG 4
Cath: RCA occlusion
ECG 5
Repeat ECG
Cath: RCA occlusion
De Winter T waves
The de Winter pattern is an STEMI-equivalent ECG finding that is characterized by
- 1-3 mm upsloping ST depression in V1-V6
- Tall symmetrical T waves
- 1-2 mm ST elevation in aVR
Though originally described in the LAD territory, de Winter T waves are actually a subset of hyperacute T waves and this pattern can appear in any coronary distribution.
ECG 1
- LAD Occlusion
ECG 2
- LAD occlusion
Terminal QRS Distortion
Terminal QRS distortion is specific marker of LAD OMI and rarely seen in early repolarization. It is defined by:
- Absence of both an S-wave and J-point notching in V2 or V3
A retrospective study by Lee et al. found that all 171 cases of early repolarization had an S-wave in V2, 90% had one in V3, and those without S waves in V3 had prominent J waves. Therefore, if precordial ST elevation is present without an S-wave or J-wave in V2 and V3 it may suggest an LAD occlusion rather than early repolarization. This only applies to leads V2-V3.
Early Repolarization
Terminal QRS Distortion
Choose One: Early repolarization or Anterior OMI?
ECG 1
ECG 2
ECG 3
ECG 4
ECG 5
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ECG 6
ECG 7
AVR STE and diffuse STD
AVR STE with diffuse STD has been classically taught as left main occlusion but in reality the differential diagnosis is broad so considering clinical presentation is important. A study by Harhash et al. evaluated 847 STEMI activations and found that of the 99 patients (12%) exhibited this pattern and only 10% of these patients had ACO (none were left main or LAD). Despite the low incidence of ACO, the in-hospital mortality rate for this group was notably high at 31%, compared to 6.2% in STEMI patients without the aVR elevation pattern.
My differential diagnosis when evaluating an ECG with AVR STE is as follows
ACO | Subendocardial Ischemia | Global Ischemia (non-coronary) | Repolarization Abnormalities |
Left main OMI | Multi-vessel CAD | Aortic syndrome | LVH with strain pattern |
pLAD OMI | Anemia, hemorrhage | LBBB, pacemaker | |
Hypoxia | Tachycardia / SVT | ||
Post cardiac arrest | Hypokalemia | ||
Massive PE, other bad stuff | Brugada, TCA, acidemia, hyperK |
ECG 1
- Critical left main stenosis & 3 vessel disease
ECG 2
- Massive pulmonary embolism
ECG 3
- Hyperkalemia
ECG 4
- TCA tox
ECG 5-6: Presenting with toe pain
- LVH with strain pattern
Aslanger Pattern
Aslanger pattern is an ECG finding that may indicate an inferior MI w/ concurrent multi-vessel disease that does not display classic contiguous STE. Instead, it presents with:
- Isolated STE in III but not in other inferior leads (II and aVF).
- STD in leads V4 to V6 (not V2) with a positive or at least terminally positive T wave
- A higher ST-segment in lead V1 than in lead V2.
The Paper
Aslanger et al (2020) studied 1000 NSTEMI, 1000 control (no MI) and about 400 inferior STEMI patients during the same time period. They found that 6.3% of patients classified as NSTEMI exhibited this pattern. These patients often had multi-vessel coronary disease, a higher risk of mortality, and a larger infarct size than typical NSTEMI patients.
Why does only 1 lead have STE?
- This finding arises from the summation of two vectors:
- ST-vector from transmural ischemia of an inferior MI (directed inferiorly)
- ST-vector caused by subendocardial ischemia (STD) from concurrent coronary disease (directed upward & away from lead II and aVF and towards AVR. Remember the net vector of subendocardial ischemia is the opposite direction of the leads with STD.
- The result is a dominant rightward vector projecting toward lead III but perpendicular to or away from the other inferior leads, thus explaining the absence of STE in leads II and aVF. In other words - in diffuse subendocardial ischemia in multi-vessel CAD there is AVR STE with diffuse depressions (left) In inferior STEMI, there are STE in II, II, avF (right). The depressions and elevations cancel out and the net vector results in an isolated STE in lead III.
Examples
ECG 1
Iso = Isoelectric ST segment
ECG 2
Source: Dr. Smith’s ECG Blog
ECG 3
Source: Dr. Smith’s ECG Blog
South Africa Flag Sign
The South African Flag Sign is an ECG pattern indicating high lateral infarction, typically due to acute occlusion of the first diagonal branch of the LAD. The pattern is characterized by:
- STE in I, avL and V2
- Reciprocal STD lead III
This pattern is often missed because leads I and aVL are not displayed contiguously on standard ECG formats, and ST elevation is seen in only one precordial lead (V2). When viewed on a 3×4 lead ECG display, the pattern visually resembles the South African national flag.
ECG 1
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ECG 2
ECG 3
New Bifascicular Block (RBBB+LAFB)
A new right bundle branch block (RBBB) and left anterior fascicle block (LAFB) may indicate a proximal LAD occlusion as both are commonly supplied by the LAD septal perforators.
RBBB Quick Review
Typical RBBB ECG findings include
- Wide QRS > 120ms
- Positive qRS (typically rSR) in V1 (may also be in V2-V3)
- Slurred S wave in V6 (also in lead I)
- In leads with V1-V3 with positive qrS, there may be discordant STD+TWI.
LAFB Quick Review
Typical LAFB ECG Findings
- Left axis deviation
- qR in leads I and avL
- rS in II, III, avF
Other clues of ischemia in RBBB+LAFB
Does every new RBBB+LAFB warrant immediate cath activation? Not necessarily. Clinical presentation plays a factor. For example, here is a patient with a RBBB+LAFB that presented with an asthma exacerbation and no chest pain. Serial troponins (and d-dimer) and were negative and patient was ultimately discharged.
Some other non-evidence based clues that may indicate ischemia in the setting of RBBB+LAFB include:
- ST deviation from typical RBBB pattern (including isoelectric ST segments in the septal/anterior leads)
- Q waves
- Patient looks like sh*t
Examples
ECG 1
ECG 2
ECG 3
ECG 4
Patient sufferred VF arrest shortly after ECG
Posterior MI
The posterior territory of the heart is supplied by branches by the LCX and RCA and posterior myocardial infarctions (PMI) are often accompanied by inferior or lateral MI. Isolated PMI is best identified by the following characteristics:
- ST Depression V1-V3
- Increased R/S ratio
- Wide R wave (>30ms)
- Upright T waves in anterior leads
A TRITON-TIMI-38 sub-analysis found that one-third of patients with isolated precordial ST depression had acute coronary occlusion (ACO), leading to worse outcomes. The DOMI-ARIGATO study further confirmed that ST depression in V1-V4 has a 97% specificity for occlusion MI. Since 2022, the ACC has officially recognized PMI as a STEMI-equivalent, reinforcing its need for early recognition and intervention.
ECG 1
ECG 2
ECG 3
ECG 4
LBBB with MI
Detecting OMI in the presence of LBBB or ventricular paced rhythm is challenging due to altered ventricular depolarization and repolarization.
LBBB Review
The ECG features of a typical LBBB is as follows
- Wide QRS > 120 ms
- Monophasic R in I and V6
- rS in V1-V2
Due to abnormal repolarization, LBBB will have STE in leads with QRS complexes that are predominantly S waves and STD in those that are predominantly R waves. This is called concordance. This can be normal in LBBB.
Concordance is when the ST segment and qrs directions are the same. There will be STE with tall R waves and STD in leads with deep S waves. This is abnormal and concerning for ischemia.
Smith Modified Sgarbossa Criteria
Smith-modified Sgarbossa criteria provide a more accurate tool for identifying LBBB and ventricularly paced rhythms than traditional Sgarbossa criteria and was validated by Meyers et al.
Examples
ECG 1
ECG 2
Tip - since modified Smith Sgarbossa does not involve absolute measurements (relies on proportionality), consider adjusting the leads to “half standard” meaasurements
ECG 3
Precordial Swirl
The precordial swirl pattern is indicative of pLAD occlusion and characterized by:
- STE and/or hyperacute T waves in V1-V2
- STE in aVR
- Reciprocal STD and/or T-wave inversion in V5-V6
This pattern reflects transmural ischemia of the anterior wall, septum, and apex and must be differentiated from LVH, LBBB, and subendocardial ischemia, which can mimic this pattern. Prospective studies are needed to validate its specificity and sensitivity in diagnosing OMI.
ECG 1
ECG 2
ECG 3
ECG 4
Conclusion
The traditional STEMI/NSTEMI framework fails to detect a significant proportion of acute coronary occlusions, leading to delayed recognition and missed opportunities for early reperfusion. By integrating these advanced high-risk, “non-STEMI” ECG findings — such as hyperacute T waves, terminal QRS distortion, Aslanger’s and modifed-Smith Sgarbossa — clinicians can improve detection, expedite intervention, and hopefully reduce mortality in this subset of patients.
Sources
- Aslanger, E., Yıldırımtürk, Ö., Şimşek, B., Şahinarslan, A., Açıkel, M., Yılmaz, M. B., ... & Karagöz, A. (2020). A new electrocardiographic pattern indicating inferior myocardial infarction with concurrent multi-vessel disease. Journal of Electrocardiology, 59, 116–122. https://doi.org/10.1016/j.jelectrocard.2020.02.006
- de Alencar Neto, J. N., Scheffer, M. K., Andrade, P. B., Caruso, L., Oliveira, A. D., Ribeiro, A. L., ... & Barbosa, M. M. (2024). Systematic review and meta-analysis of diagnostic test accuracy of ST-segment elevation for acute coronary occlusion. International Journal of Cardiology, 392, 112–119. https://pubmed.ncbi.nlm.nih.gov/38382857/
- de Winter, R. J., Verouden, N. J., Wellens, H. J., & Wilde, A. A. (2008). A new ECG pattern without ST-elevation indicating proximal LAD occlusion. New England Journal of Medicine, 359(19), 2071–2073. https://doi.org/10.1056/NEJMc0804737
- DOMI-ARIGATO Study. (2021). High specificity of V1-V4 ST depression for occlusion myocardial infarction. Journal of the American Heart Association, 10(12), e022866. https://www.ahajournals.org/doi/full/10.1161/JAHA.121.022866
- Dr. Smith’s ECG Blog. (n.d.). ECG cases and occlusion MI. Retrieved from https://hqmeded-ecg.blogspot.com/
- Fourth Universal Definition of Myocardial Infarction. (2018). Journal of the American College of Cardiology, 72(18), 2231–2264. https://doi.org/10.1016/j.jacc.2018.08.1038
- Harhash, A. A., Huang, S. S., Mando, R., Eltahawy, E., Elshazly, M. B., Tuzcu, E. M., & Kapadia, S. R. (2019). ST-segment elevation in lead aVR with diffuse ST-depression: Clinical significance and relationship to acute coronary occlusion. The American Journal of Cardiology, 124(1), 28–34. https://pubmed.ncbi.nlm.nih.gov/30639554/
- Hung, M. J., Hu, P., & Hung, M. Y. (2018). Prognostic value of occluded culprit arteries in patients with NSTEMI: A meta-analysis of 25 studies. American Journal of Medicine, 131(2), 163-171. https://pubmed.ncbi.nlm.nih.gov/29422071/
- Lee, K. W., Ahn, S. G., Lee, H. I., Kim, J. Y., Ro, Y. M., & Lee, S. H. (2016). Terminal QRS distortion in anterior ST-elevation myocardial infarction: A highly specific ECG marker of acute coronary occlusion. The American Journal of Emergency Medicine, 34(1), 119–125. https://doi.org/10.1016/j.ajem.2015.09.017
- Life in the Fast Lane (LITFL). (n.d.). ECG Library. Retrieved from https://litfl.com/ecg-library/
- Meyers, H. P., Bracey, A., Lee, D., Hoellerich, V. L., Hernandez, M., & Smith, S. W. (2015). Validation of the modified Sgarbossa criteria for acute coronary occlusion in the presence of left bundle branch block. Journal of the American College of Cardiology, 66(4), 415-423. https://doi.org/10.1016/j.jacc.2015.05.049
- Ricci, B., Aslanger, E., McCabe, J. M., Sattar, Y., Smith, S. W., & Myers, H. P. (2024). ECG patterns of occlusion myocardial infarction: A narrative review. Annals of Emergency Medicine, 83(1), 50-63. https://doi.org/10.1016/j.annemergmed.2024.01.012
- Smith, S. W., Dodd, K. W., Henry, T. D., & Dvorak, D. M. (2012). Improving ECG diagnosis of acute coronary occlusion in the presence of left bundle branch block: The modified Sgarbossa criteria. Annals of Emergency Medicine, 60(6), 766-776. https://doi.org/10.1016/j.annemergmed.2012.06.027
- Surawicz, B., & Knilans, T. K. (1973). Electrocardiography in clinical practice. Circulation, 47(1), 8-17. https://www.ahajournals.org/doi/10.1161/01.cir.47.1.8
- TRITON-TIMI-38 Trial. (2010). Subanalysis of ST-depression in NSTEMI. The American Journal of Medicine, 123(6), 579-585. https://www.sciencedirect.com/science/article/pii/S1936879810003833
This post is for educational purposes and not medical advice.