In LBBB, ST elevation of 1 mm or more in a lead where the QRS is positive (concordant), which LBBB alone never does.
LBBB hides an infarct because its own ST segments are already shifted opposite the QRS. So Sgarbossa's criteria look for what LBBB alone doesn't do. Concordant ST elevation of 1 mm or more in a lead with a positive QRS scores 5 points. Concordant ST depression of 1 mm or more in V1-V3 scores 3 points. Excessively discordant ST elevation, originally over 5 mm, scores 2 points; in the Smith-modified criteria it's 25% or more of the S wave before it. Three points or more is about 90% specific for infarction.
Each is a standard 12-lead: 2.5 seconds of each lead in four columns, with 10 seconds of lead II along the bottom, drawn to scale (25 mm a second, 10 mm a millivolt). The measurements are under each one.
A QRS of 0.12 s or more with a deep, broad S (QS or rS) in V1 and a broad R with no Q wave in I, aVL, V5 and V6.
ST elevation in I, aVL, V5 and V6, with reciprocal depression in III and aVF.
ST elevation across V1-V4, from an occluded left anterior descending artery.
The ECG tool in the app gives you a new 12-lead every time and walks you through reading it: rate, QRS, axis, then where the ST is up and down. It's part of the Paramedic level, and you can try 5 ECGs a day free.
Try the 12-lead drill
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