Here’s an oldie but a goodie!
This is just a quick entry to review something that commonly comes up in the ED. You’re given an EKG that shows LBBB (for the sake of this discussion lets say it is old) and you are wondering how you can tell if there is acute MI. The Sgarbossa Criteria help with that determination. The picture above is the best illustration I could find. With most LBBB’s there is what is called appropriate disconcordance. The first thing you have to do is determine the direction of the major QRS deflection. The first complex above is “up,” the second is “down” and the third is “down.” The Sgarbossa Criteria say that if there is more than 5mm elevation in the opposite direction of the major QRS deflection in any one lead you can call this an acute MI (middle tracing above.) They also state that if there is more than 1mm deflection in the same direction as the major QRS in any one lead you can call it an acute MI.
One thing to mention though is that sometimes patients will have a very deep S-wave (think LVH.) If you have a really deep S-wave you will by default have higher ST segment elevation. In this case a more specific marker is discordant ST segment elevation > 0.25 the depth of the S wave (see below.)
1. Elena.B.Sgarbossa et al; New England Journal of Medicine, Volume 334 ;Number 8, FEBRUARY 22, 1996.