Sgarbossa Criteria for MI in LBBB
Identifies acute MI in the presence of left bundle branch block from 3 weighted ECG criteria (Sgarbossa 1996; score ≥ 3 positive). The Smith-modified rule replaces the ≥ 5 mm discordant ST elevation criterion with an ST/S ratio ≤ −0.25 and is unweighted.
Score interpretation
Score < 3: Sgarbossa criteria not met. The rule has low sensitivity — MI in LBBB is not excluded.
→ Clinical correlation essential. Serial ECGs and troponins; consider the Smith-modified criteria. If high clinical suspicion for ACS, arrange urgent cardiology review per local STEMI-equivalent protocol.
Score ≥ 3: specificity about 90% for acute MI in LBBB (Sgarbossa 1996). Treat as a STEMI equivalent.
→ Immediate cardiology / primary PCI discussion per local STEMI-equivalent protocol; ACS treatment per protocol.
Interpretation bands for the Sgarbossa. Apply clinical judgement and local guidance.
References
- Sgarbossa EB, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. N Engl J Med. 1996;334(8):481–487.
- Smith SW, et al. Diagnosis of ST-elevation myocardial infarction in the presence of left bundle branch block with the ST-elevation to S-wave ratio in a modified Sgarbossa rule. Ann Emerg Med. 2012;60(6):766–776.
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Curated clinical cross-links plus same-class fallbacks.
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Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.