ECG: Sgarbossa Criteria for LBBB and AMI

It is difficult to determine if a patient with a left bundle branch block (LBBB) has an acute myocardial infarction (AMI) because ST segments are "appropriately discordant" with the terminal portion of the QRS.

• The major, terminal portion of the QRS complex will normally be “appropriately discordant” with the ST segment.

Sgarbossa criteria

• For detecting an AMI in the setting of a LBBB
• Derived from the GUSTO-1 trial
• Sgarbossa criteria are NOT perfect in screening for AMI
• Use as another data point in risk-stratifying these complex patients with LBBB
• Sgarbossa criteria applies also for LBBB pattern seen in pacemaker patients

1. ST elevation ≥ 1 mm concordant with QRS complex

• Most predictive of AMI
• + LR: 9.54 (3.1-17.3)
• - LR: 0.3 (0.22-0.39)

2. ST depression ≥ 1 mm in lead V1, V2, V3

• + LR: 6.58 (2.6-16.1)
• - LR: 0.78 (0.7-0.87)

3. ST elevation ≥ 5 mm where discordant with QRS complex

• May not be significant as the +LR crosses 1.0
• + LR: 3.42 (0.18-6.5)
• - LR: 0.8 (0.72-0.9)

ECG tracings courtesy of ems12lead.blogpost.com

Modified Sgarbossa Rule (updated 01/01/2013)

Smith SW et al. Ann Emerg Med 2012

Rule:

• Ratio of ST-elevation / S-wave < -0.25 is indicative of acute MI
• The modified Sgarbossa Rule uses proportions to identify acute AMI in the setting of ST-elevations in LBBB (helpful in low-voltage EKG)

| | Sensitivity | Specificity | (+) LR | (-) LR | | ----------------------- | :-------------: | :-------------: | :--------: | :--------: | | Modified Sgarbossa rule | 91% | 90% | 9.0 | 0.1 |

Fagan nomogram

References

• Sgarbossa EB et al, for GUSTO-1 investigators. ECG diagnosis of evolving AMI in the presence of LBBB, New Engl J Med 1996; 334:481-7. [Source]
• 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 Dec;60(6):766-76 [PubMed]