Left Bundle Branch Blocks (LBBB) are uniquely challeging at interpreting for ischemic changes.
ST changes are frequently seen in with LBBB that may or may not be related to ischemia.
LBBB are always considered pathological but are not always associated with a myocardial infarction. Decisions regarding thrombolysis and cath lab activation can be difficult.
Sgarbossa criteria first described by Elena Sgarbossa offers another tool for assessing for ischemic changes in the context of a LBBB or ventricular paced rhythm.
Criteria
Concordant ST-Elevation of 1 or more mm = 5 points
Concordant ST-depression of 1 or more mm in V1-V3 = 3 points
Discordant ST-elevation of more that 5 mm = 2 points
Score of 3 or more has a 90% specificity for myocardial infarction. Not sensitive.
Example 1
Typical LBBB
Concordant ST elevation in the aVF
Patient ended having an 100% occluded RCA
Example 2
Baseline EKG
Shows atrial-sensed and ventricular paced rhythm
Same patient but now presenting with chest pain
Note concordant ST elevation in the inferior leads(III, aVF).
References
Sgarbossa E.B. et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1. N Engl J Med Feb 1996.