EBQ:Sgarbossa Criteria Study

Complete Journal Club Article

Sgarbossa E. et al.. "Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators". NEJM. 1996. 334(8):481-7.
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Clinical Question

How can we diagnose Acute Myocardial Infarction in patients with a Left Bundle Branch Block?

Conclusion

Sgarbossa's Criteria is a validated clinical prediction rule based on ECG criteria to diagnose Acute Myocardial Infarction in patients with a Left Bundle Branch Block. It has good specificity, but poor sensitivity.

Major Points

The Sgarbossa Criteria:

1. ST-segment Elevation of at least 1 mm with concordance with the QRS complex with a score of 5
2. ST-segment depression in leads V1, V2 or V3 with a score of 3
3. ST-segment Elevation of atleast 5 mm with discordance with the QRS complex with a score of 2

With a score >3 90% of those with positive criteria will have STEMI (Good Specificity) But with negative criteria it doesn't help that much (Low sensitivity)

ECGs of patients with confirmed MIs from the GUSTO-1 trial were blindly compared with ECGs of control patients with LBBB from the Duke Databank for Cardiovascular Disease. The ECG criteria for MI in the presence of LBB was then tested against patients with chest pain and acute LBBB.

Criteria

Original Criteria

Sgarbossa's Original Criteria

≥3 points = 98% probability of STEMI

• ST elevation ≥1 mm in a lead with upward QRS complex (concordant) - 5 points
• ST depression ≥1 mm in lead V1, V2, or V3 - 3 points
• ST elevation ≥5 mm in a lead with downward QRS complex (discordant) - 2 points

Smith's modification

Smith's Modified Sgarbossa 3rd Rule

• Changes the 3rd rule of original Sgarbossa's Criteria to be ST depression OR elevation discordant with the QRS complex and with a magnitude of at least 25% of the QRS
  • Increases Sn from 52% → 91% at the expense of reducing Sp from 98% → 90%

Population

Patient Demographics

• Median Age: 68 years
• Males: 64% in study group and 60% in experimental group
• Left Axis Deviation: 28% Vs. 48%
• Previous MI: 26% Vs. 59%

Inclusion Criteria

• Experiment: Patients with LBBB and Acute myocardial infarction (GUSTO-1 trial population)
• Control: Patients with normal documented angiography with LBBB Randomly selected from Duke data bank for cardiovascular disease
• Validation Segment: 22 patients with elevated CKMB and 23 patients with unstable angina (control patients)

Exclusion Criteria

Patients without LBBB

Outcomes

• Using univariate analysis the ods rations for the individual criteria for STEMI in the presence of LBBB were:

Criteria	Odds Ratio	Score
ST-segment elevation ≥ 1mm and concordant with QRS complex	25.2 (11.6-54.7)	5
ST-segment depression ≥ 1mm in lead V1, V2, V3	6.0 (1.9-19.3)	3
ST-segment elevation ≥ 5mm and discordant with QRS complex	4.3 (1.8-10.6)	2

Validation Segment for Sgarbosa Score ≥3 to determine prescience of a STEMI

Derivation sample vs Validation Sample

• Sensitivity: 78% vs 36%
• Specificity: 90% vs 96%
• Pos. Likelihood ratio: 7.8 vs. 9.0
• Neg. Likelihood ratio: 0.2 vs 0.7

Primary Outcome

Acute Myocardial Infarction

Criticisms & Further Discussion

• The Sgarbossa criteria have not been incorporated into the AHA STEMI guidelines and new LBBB has been removed from the current AHA recommendations for activation of PCI.

• Although the criteria is highly specific it lacks sensitivity and can result in false positive catheterization lab activation.

Funding

Grant from Bayer, Genentech, CIBA–Corning, ICI Pharmaceuticals, and Sanofi Pharmaceuticals.

See Also

• Sgarbossa's criteria