Recall, in LBBB we expect appropriate discordance (‘appropriate’ as opposed to ‘excessive’), i.e. the ST segments and T waves will deflect in the opposite direction of the QRS complex
tl;dr: concordance is bad, excessive discordance is also bad
Modified Sgarbossa Criteria
≥ 1 lead with ≥ 1 mm of concordant ST elevation (check all leads! concordant ST elevation in any single lead may suggest AMI)
≥ 1 lead of V1-V3 with ≥ 1 mm of concordant ST depression
≥ 1 lead anywhere with ≥ 1 mm STE and proportionally excessive discordant STE (defined by ≥ 25 of the depth of the preceding S-wave)