Activate or Wait – 006
62 year-old woman with two hours of central crushing chest pain. Smoker, hypertension.
ETA 30 minutes.
Would you activate your cath lab/STEMI protocol?
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ECG interpretation
Anterolateral OMI
- ST elevation in V2-6, with an extremely low preceding QRS amplitude
- Inferior reciprocal ST depression
- Hyepracute T waves (HATW) in aVL, V4-6. The area under the curve relative to the QRS size is more important than the height in HATW, which often present initially as wide, bulky T waves
- Terminal QRS distortion in V2-3: defined by the absence of both an S wave and J wave in either lead V2 or V3
Remember, ST elevation is always proportional the QRS. The ST elevation seen here is far more than what could possible be called “normal” in proportion to this tiny QRS. Check out what happens if we make the QRS of decent amplitude:
A second ECG was performed en route, confirming suspicions
AI interpretation by PMcardio
PMcardio’s AI ECG model identified a STEMI/STEMI equivalent.
The explainability feature offers insights into problematic patterns in the respective leads, providing a clear rationale for the diagnosis.
Further reading
Outcome
Key Finding:
Occluded mid left circumflex artery artery
Findings:
- Left Main Coronary Artery – mild irregularities.
- Left Anterior Descending Coronary Artery – mild irregularities.
- Left Circumflex Coronary Artery – large calibre vessel. Non-dominant. 99% stenosis in mid vessel. Culprit.
- Right Coronary Artery – large calibre vessel. dominant. Mild irregularities.
Plan:
- Single vessel coronary artery disease. 99% stenosis left circumflex.
- Percutaneous coronary intervention to mid left circumflex with drug eluting stent
Clinical Pearls
In the previous case (005), we discussed the four-variable subtle anterior STEMI formula as a tool to differentiate normal variant elevation from LAD occlusion.
Terminal QRS distortion is another, more rapidly identifiable feature that can differentiate between the two. It is defined by the absence of an S wave and J wave in either of leads V2 or V3.
Let’s compare two examples.
1. Benign early repolarisation (BER) – no terminal QRS distortion
2. LAD occlusion – terminal QRS distortion
References
Further reading
- Lee DH, Walsh B, Smith SW. Terminal QRS distortion is present in anterior myocardial infarction but absent in early repolarization. Am J Emerg Med. 2016 Nov;34(11):2182-2185
- Smith SW. Best Explanation of Terminal QRS Distortion in Diagnosis of Electrocardiographically Subtle LAD Occlusion. Dr Smith’s ECG blog.
- Driver BE, Khalil A, Henry T, Kazmi F, Adil A, Smith SW. A new 4-variable formula to differentiate normal variant ST segment elevation in V2-V4 (early repolarization) from subtle left anterior descending coronary occlusion – Adding QRS amplitude of V2 improves the model. J Electrocardiol. 2017 Sep-Oct;50(5):561-569.
- Bozbeyoğlu E, Aslanger E, Yıldırımtürk Ö, Şimşek B, Karabay CY, Şimşek MA, Tekkeşin Aİ, Değertekin M, Kozan Ö. A tale of two formulas: Differentiation of subtle anterior MI from benign ST segment elevation. Ann Noninvasive Electrocardiol. 2018 Nov;23(6):e12568.
- Burns E, Buttner R. Anterior Myocardial Infarction. LITFL
- Burns E, Buttner R. T wave. LITFL
- Nickson C. STEMI Management. LITFL
Online resources
- Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
- Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
- Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
- Smith SW. Dr Smith’s ECG blog.
- Rawshani A. Clinical ECG Interpretation ECG Waves
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EKG Interpretation
