From the Guidelines
To diagnose a STEMI in the presence of a left bundle branch block (LBBB), the Sgarbossa criteria are primarily used, as stated in the 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline for the management of patients with acute coronary syndromes 1. The Sgarbossa criteria help identify acute myocardial infarction despite the baseline ECG changes caused by LBBB.
- The original Sgarbossa criteria include:
- ST-segment elevation ≥1 mm that is concordant with (in the same direction as) the QRS complex
- ST-segment depression ≥1 mm in leads V1, V2, or V3
- ST-segment elevation ≥5 mm that is discordant with (in the opposite direction of) the QRS complex A score of ≥3 points suggests acute MI. The modified Sgarbossa criteria replace the third criterion with a ratio of ST-segment elevation to S-wave amplitude of ≤-0.25 (or ≥25% of the S wave depth), which improves diagnostic accuracy, as supported by the 2006 clinical policy on indications for reperfusion therapy in emergency department patients with suspected acute myocardial infarction 1. These criteria are essential because LBBB normally causes secondary ST-T changes that can mimic or mask a STEMI, making standard STEMI criteria unreliable, as noted in the 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction 1. When these criteria are met in a patient with chest pain and LBBB, urgent reperfusion therapy should be considered, as timely intervention significantly improves outcomes in acute myocardial infarction.
From the Research
STEMI LBBB Criteria
The criteria used to diagnose STEMI in patients with Left Bundle-Branch Block (LBBB) is a topic of interest in the medical field.
- The Sgarbossa electrocardiography criteria are the most validated tool to aid in the diagnosis of STEMI in the presence of LBBB 2.
- A Sgarbossa score of ≥3 has a superb specificity (98%) and positive predictive value for acute myocardial infarction and angiography-confirmed acute coronary occlusion 2.
Diagnosis and Triage Algorithm
A diagnosis and triage algorithm incorporating the Sgarbossa criteria can quickly and accurately identify patients with acute coronary artery occlusion 2.
- This algorithm can help reduce false catheterization laboratory activation and inappropriate fibrinolytic therapy 2.
- The 2013 STEMI guideline removed previous recommendations for emergent reperfusion therapy in patients with suspected ischemia and new or presumably new LBBB, which may deny reperfusion therapy to a high-risk population 2.
Reperfusion Therapy
Reperfusion therapy is a crucial aspect of STEMI treatment, and the choice between primary percutaneous coronary intervention (PCI) and fibrinolysis depends on various factors 3, 4, 5, 6.