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. 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. 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, 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:

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 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 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. 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.

st-s ratio figure 1

Although the Smith-modified criteria have yet to be validated, this modification has been included in the rather useful MDCalc calculator and incorporated into a proposed amendment to the 2013 ACC/AHA STEMI guidelines that has been co-authored by Dr Sgarbossa herself. In their algorithm, they propose that if full Sgarbossa criteria are not met, then the presence of discordant ST elevation with a ratio of 0.25 relative to the S wave should still be grounds for PCI activation.

mod_sgarbossa_algorithm

Interestingly in this case, although the ECG meets Sgarbossa criteria, it does not meet the Smith-modified Sgarbossa criteria as the S waves are high amplitude. This patient had a troponin rise, but did not proceed to angiography, so we’ll never know the extent of the coronary artery disease.

What do the Guidelines say?

The Australian guidelines are due for a refresher. The current version is from 2006, with a significant addendum added in 2011. This guideline (in an easy algorithm format here) still includes new LBBB as a STEMI equivalent, and does not include the Sgarbossa criteria.

As mentioned above, the 2013 ACC/AHA guidelines have removed new or presumed new LBBB as an indication for PCI, but also do not include any of the Sgarbossa criteria.

Which leaves me with a final question... is it a STEMI or a STEACS?