An ECG Case: Left Bundle Branch Block and Possible STEMI, What to Do?
A male in his mid 40’s presented to the ED with 20 minutes of chest pain. He had no previous cardiac disease.
The ECG shows sinus rhythm with left bundle branch block (LBBB).
QRS is wide (> 120 ms)
Wide upright R-waves in lateral leads I, aVL and V6, with “discordant” ST depression
Small r-wave in V1-V3 and a deep S-wave, with “discordant” ST elevation.
Small r-wave in aVF, with small amount “concordant” ST elevation.
Small r-wave in III, with small amount “discordant” ST elevation.
In the past guidelines for STEMI management recommended reperfusion therapy (PCI or fibrinolytic, as appropriate) with chest pain and new LBBB. However, only approximately 2-4% of such patients have acute coronary occlusion. Thus, the use of the Sgarbossa criteria is now recommended to help decision making in this situation. The original Sgarbossa criteria have been modified to improve sensitivity.
Here are the original criteria:
Concordant ST elevation > 1 mm in leads with a positive QRS complex (score: 5 points).
Concordant ST depression > 1 mm in lead V1-V3 (score: 3 points).
Excessively discordant ST elevation > 5 mm in leads with a negative QRS complex (score: 2 points).
A total score of ≥3 points is considered a positive Sgarbossa criteria, suggesting a high likelihood of myocardial infarction.
The third criterion was modified to improve sensitivity:
Proportionally excessive discordant ST elevation of > 1 mm anywhere, as defined by ≥ 25% of the depth of the preceding S-wave.
The Modified Sgarbossa criteria are unweighted. Yes, to any criteria is deemed 80% sensitive and 99% specific in identifying acute coronary occlusion in LBBB.
Back to our case, using the Modified Sgarbossa Criteria.
Subtle concordant ST elevation in lead aVF, almost 1 mm.
2 mm of discordant ST elevation in lead III. Since the S-wave is only 3 mm, this is proportionally excessively discordant ST elevation.
This patient is likely having a STEMI.
