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Sgarbossa et al, initially identified patients with MI and left bunde branch block (LBBB) from the GUSTO trial; these ECGs were compared to the ECGs of patients with chronic CAD and LBBB
LBBB is defined by 3 criteria QRS >125msec, V1- QS or rS, and R wave peak time 60ms with no q wave in leads I, V5, V6
After a criteria to identify MI with LBBB was estabilshed it was tested on patients presenting with chest pain and
The study resulted in Sgarbossa criteria; 3 independent predictors of MI in setting of LBBB
1.) ST segment concordance of 1mm any lead (greatest odd ratio, i.e. most specific) 2.) ST depression 1mm V1- V3
3.) Excessive ST discordance greater than 5mm (lowest odds ratio)
References
Sgarbossa E, et al. ELECTROCARDIOGRAPHIC DIAGNOSIS OF EVOLVING ACUTE MYOCARDIAL INFARCTION IN THE PRESENCE OF LEFT BUNDLE-BRANCH BLOCK. NEJM Feb 22, 1996: Vol 334; No. 8