From the Guidelines
The Sgarbossa-Smith criteria are a set of diagnostic tools used to identify acute myocardial infarction (AMI) in patients with left bundle branch block (LBBB) or ventricular paced rhythm on electrocardiogram (ECG), with the criteria including ST-segment elevation ≥1 mm concordant with the QRS complex, ST-segment depression ≥1 mm in leads V1-V3, and a proportional measurement of ST elevation to S-wave ratio ≤-0.25 in at least one lead 1. The criteria were developed to help clinicians diagnose AMI in patients with LBBB, as the typical ECG changes of AMI can be obscured by the LBBB pattern.
- The original Sgarbossa criteria, as reported by Sgarbossa et al in the GUSTO-1 trial, include three key findings: + ST-segment elevation of 1 mm or more and concordant with the QRS complex + ST-segment depression of 1 mm or more and concordant with the QRS in one or more precordial leads V1 through V3 + ST-segment elevation of 5 mm or more in discordant leads
- These criteria have been modified by Smith to improve accuracy, with the third criterion replaced by a proportional measurement: ST elevation to S-wave ratio ≤-0.25 in at least one lead 1. The Sgarbossa-Smith criteria work by identifying ST-segment changes that are disproportionate to what would be expected from LBBB or pacing alone, suggesting true myocardial injury rather than secondary repolarization abnormalities.
- When using these criteria, it's essential to also consider clinical context, cardiac biomarkers like troponin, and other diagnostic modalities to ensure accurate diagnosis and appropriate management of patients with suspected AMI 1.
From the Research
Sgarbossa Criteria
The Sgarbossa criteria are a set of electrocardiographic (ECG) criteria used to diagnose ST-segment elevation myocardial infarction (STEMI) in patients with left bundle branch block (LBBB) or ventricularly paced rhythms. The criteria were first proposed by Sgarbossa et al. and have since been modified and refined.
Original Sgarbossa Criteria
The original Sgarbossa criteria consist of three components:
- ST-segment elevation ≥ 1 mm in leads with a positive QRS complex (concordant ST elevation)
- ST-segment depression ≥ 1 mm in leads V1-V3 (anterior ST depression)
- ST-segment elevation ≥ 5 mm in leads with a negative QRS complex (discordant ST elevation) 2
Modified Sgarbossa Criteria
The modified Sgarbossa criteria replace the third component with a new criterion:
- ST-segment elevation to S-wave ratio (ST/S ratio) ≤ -0.25 in leads with a negative QRS complex (discordant ST elevation) 3 This modified criterion has been shown to improve the diagnostic utility of the Sgarbossa criteria for STEMI in patients with LBBB.
Diagnostic Utility
The Sgarbossa criteria have been shown to have good diagnostic utility for STEMI in patients with LBBB, with a sensitivity of 20-91% and a specificity of 90-98% 3, 2, 4. However, the criteria are not perfect and may be limited by factors such as the presence of ventricular pacing or other ECG abnormalities.
Clinical Applications
The Sgarbossa criteria are useful in clinical practice for diagnosing STEMI in patients with LBBB or ventricularly paced rhythms. They can help identify patients who require urgent reperfusion therapy, such as percutaneous coronary intervention (PCI) or thrombolysis. However, the criteria should be used in conjunction with other clinical and ECG findings to ensure accurate diagnosis and treatment 5, 6.
Key Points
- The Sgarbossa criteria are used to diagnose STEMI in patients with LBBB or ventricularly paced rhythms.
- The original criteria consist of three components, including concordant ST elevation, anterior ST depression, and discordant ST elevation.
- The modified Sgarbossa criteria replace the third component with a new criterion based on the ST/S ratio.
- The criteria have good diagnostic utility, but may be limited by factors such as ventricular pacing or other ECG abnormalities.
- The Sgarbossa criteria are useful in clinical practice for diagnosing STEMI and guiding treatment decisions 3, 5, 6, 2, 4.