Summary by Alex Chen, MD
The original Sgarbossa criteria have a high specificity (96%) but low sensitivity (36%), meaning it is useful when positive, but a negative result does not rule out MI. The modified Sgarbossa criteria by Smith et al., have a much better sensitivity (91%) with a slight decrease in specificity (90%). You should apply the modified Sgarbossa criteria to evaluate for MI in LBBB and paced rhythms.
Why does this matter?
It’s challenging to read STEMI in the setting of LBBB. Sgarbossa Criteria can help. The modified Sgarbossa criteria may help even more. This was a case report in JAMA Internal Medicine, with an illustrative ECG. Today’s post is to help drive home this core concept in ECG interpretation.
“One ECG begets another.” –Dr. Corey Slovis
Question: How would you read this ECG?
Sgarbossa Criteria (≥3 is considered positive):
CONCORDANT ST elevation ≥1mm that is 5 points
CONCORDANT ST depression ≥1mm in V1-V3 that is 3 points
DISCORDANT ST elevation ≥5mm that is 2 points
Modified Sgarbossa (any one criteria is considered positive):
First and second criteria are the same.
The third criterion is changed to ST elevation to S wave amplitude ratio ≥ 0.25 (Figure B below).
Answer: Interestingly, the ECG for this case report shows development of conventional STEMI criteria in the patient’s native beats (QRS complex 9, leads V5 and V6). This ECG is unique in that it is negative by the original Sgarbossa criteria of the paced beats but is positive based on the modified Sgarbossa criteria. Namely, QRS complex 10 in lead V6 has ST elevation 2.5mm/S-wave 6mm = 0.42; this is >25% (or 0.25).
REBEL EM has a post on the external validation study for the modified Sgarbossa criteria.
Enhancing the Sgarbossa Criteria for the Diagnosis of ST Elevation Myocardial Infarction. JAMA Intern Med. 2019 Feb 11. doi: 10.1001/jamainternmed.2018.7993. [Epub ahead of print]
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Reviewed by Thomas Davis