What are the Sargbossa (Sgarbossa) criteria for diagnosing acute myocardial infarction (AMI)?

Sgarbossa Criteria for Diagnosing Acute Myocardial Infarction

The Sgarbossa criteria are a validated set of ECG findings used to diagnose acute myocardial infarction (AMI) in patients with left bundle branch block (LBBB) or ventricular paced rhythms, with the modified Sgarbossa criteria showing superior diagnostic performance with a sensitivity of 91% and specificity of 90%.

Original Sgarbossa Criteria

The original Sgarbossa criteria consist of three ECG findings, each assigned a point value:

1. Concordant ST elevation ≥1 mm in any lead (5 points)

   • ST elevation occurring in the same direction as the QRS complex
   • Highly specific (98%) for AMI

2. Concordant ST depression ≥1 mm in leads V1-V3 (3 points)

   • ST depression in leads that normally show dominant S waves
   • Highly specific for posterior wall involvement

3. Excessive discordant ST elevation ≥5 mm in leads with negative QRS complexes (2 points)

   • ST elevation in the opposite direction of the predominant QRS
   • Less specific than the other criteria

A score of ≥3 points indicates high likelihood of AMI and warrants immediate consideration for reperfusion therapy 1.

Modified Sgarbossa Criteria

The modified Sgarbossa criteria improve diagnostic accuracy by replacing the third criterion with a proportional measurement:

1. Concordant ST elevation ≥1 mm in any lead
2. Concordant ST depression ≥1 mm in leads V1-V3
3. Proportionally excessive discordant ST elevation: ST/S ratio ≤ -0.25
   • This means the ST elevation (measured at the J-point) is at least 25% of the depth of the preceding S wave
   • Significantly improves sensitivity while maintaining high specificity 1, 2

Any positive criterion from the modified Sgarbossa criteria is considered diagnostic for AMI, eliminating the need for a point system 1, 3.

Clinical Application

When evaluating patients with suspected AMI who have LBBB or ventricular paced rhythms:

• Obtain a 12-lead ECG immediately
• Apply the modified Sgarbossa criteria to identify potential AMI
• If any criterion is positive, activate cardiac catheterization lab immediately
• Do not wait for troponin elevation if criteria are positive, as early reperfusion saves myocardium 1

Special Considerations

• Posterior MI: Consider obtaining posterior leads (V7-V9) if suspecting posterior wall involvement, especially with ST depression in V1-V3 1
• False negatives: The absence of Sgarbossa criteria does not rule out AMI; clinical judgment remains important 1, 4
• Pacemaker reprogramming: In non-dependent patients, consider temporarily reprogramming the pacemaker to allow evaluation of intrinsic rhythm, but do not delay invasive investigation if criteria are positive 1

Diagnostic Performance

• Original Sgarbossa criteria: Sensitivity 18-53%, specificity 82-94% 1, 5
• Modified Sgarbossa criteria: Sensitivity 91%, specificity 90%, positive likelihood ratio 9.0 1, 2

The modified Sgarbossa criteria provide a practical approach to risk stratify this diagnostically challenging high-risk group and optimize acute therapy for patients with LBBB or ventricular paced rhythms who are experiencing AMI 1, 5.