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  • Sgarbossa Criteria in LBBB

    Michael Edmonds

    The Sgarbossa Criteria

    You’ll all recall that the identification of a STEMI in the setting of an old LBBB can be made using the Sgarbossa criteria, described in 1996 (Sgarbossa 1996). The significance of a presumed new LBBB seems to have been overstated in the past, with this now being removed from the 2013 ACC/AHA STEMI guidelines as an indication for PCI due to poor accuracy (O 2013). It is suggested that the Sgarbossa criteria can be used to evaluate the likelihood of STEMI in any LBBB, presumed new or old.

    Life in the Fast Fane, as in most things, has a great summary on this (http://lifeinthefastlane.com/ecg-library/basics/sgarbossa/), and the crux of the matter is that you can call a STEMI in the presence of a LBBB (be it old or presumed new) if you score ≥ 3 points (Figure \ref{fig:criteria}):

    • Concordant ST elevation > 1mm in leads with a positive QRS complex (5 points)

    • Concordant ST depression > 1 mm in V1-V3 (3 points)

    • Excessively discordant ST elevation > 5 mm in at least two leads with a negative QRS complex (2 points each)

    Sgarbossa criteria definitions \label{fig:criteria}

    Sgarbossa Pearl: You can apply these criteria to paced rhythms with a LBBB appearance (although less specific)

    One of the main limitations of the Sgarbossa criteria is a low sensitivity, in the realms of 20%. This means that a lot of STEMIs may be missed with this rule (but this is still better than not trying to interpret the LBBB for STEMI at all!).

    The Modified Sgarbossa Criteria

    Dr Smith of Dr Smith’s ECG Blog has pointed out that an absolute measurement of 5mm as a criteria reduces sensitivity and specificity and argues that this criteria should be based on discordant elevation greater than 0.25 of the S wave amplitude (Figure \ref{fig:smith_mods}; (Smith 2012)). Using this instead of the 5mm criterion as the “Smith-modified Sgarbossa criteria” improved diagnostic accuracy and sensitivity in their study, reporting a positive likelihood ratio of 9 and negative likelihood ratio of 0.1. This is annotated, a little confusingly to me, as ST/S ≤ -0.25. That is, the positive deflection of the ST segment is more than a quarter of the negative deflection of the S. It is argued that any excessively discordant ST segment based on proportion (ST elevation or depression) could be interpreted as diagnostic of STEMI.