Acute MI? w/ LBBB- Sgarbossa's Criteria

It's hard to tell if a patient with LBBB  has an acute MI because ST segments are "appropriately discordant" with the terminal portion of the QRS

• i.e., if  QRS is - (downgoing), the ST will normally be + (upgoing), and vice versa

In 1996, Sgarbossa et al looked through the GUSTO-1 trial patients with LBBB and AMI --> derived 3 criteria to help dx "hidden" AMI:

1. ST elevation ≥ 1 mm concordant with QRS complex (most predictive of AMI of the 3 criteria)
2. ST depression ≥ 1 mm in lead V1, V2, or V3
3. ST elevation ≥ 5 mm where discordant with QRS complex

 

Sources:

• http://academiclifeinem.blogspot.com/2010/11/paucis-verbis-sgarbossas-criteria-with.html?m=1 
• http://www.ems12lead.blogspot.com