Posted by Nick Taylor on January 13, 2016 at 5:35 am
So this is a Left Bundle Branch Block with signs of anterior STEMI.
The practical take home message for LBBB is that ST segments and TWs always go in the opposite direction to the main QRS forces.
Thus by these simple rules , the lateral leads here are abnormal and thus ischaemic…there are dominant R waves in V4 and V5 associated with ST elevation, not depression, thus this is a STEMI. There are of course more scientific ways to determine STEMI in LBBB.
“new” LBBB is rarely new and uncommonly associated with acute CA occlusion (2.4%) thus now not in guidelines.
Sgarbossa criteria have low sensitivity (sens 20%-75%, spec 90%)
This led to improved Sgarbossa by Steven Smith and co
Derived Smith-Modified Criteria, published in 2012 in Annals of EM
1. at least 1 mm of concordant ST elevation in at least one lead
2. at least 1 mm of concordant ST depression in at least one of leads V1-V3
3. at least 1 mm of discordant ST elevation AND an ST elevation to S-wave ratio of at least 25% in at least one lead.
Sens 90%, spec 90% for any one of these 3 ( Smith et al changed Sgarbossa weighted 3rd criteria to this 25% one)
In this example 1. and 3. are present, clearly a STEMI
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