Sgarbossa Criteria and Concordance vs Discordance in simple words.

Created by team@ekgdx.com on Jan. 3, 2024

Today's article is about the Sgarbossa Criteria and Concordance vs Discordance in simple words. 

The objective of this blog post is to clarify many doubts in a simple, graphic and didactic way that still persist on this topic.

Individuals suspected of having a myocardial infarction (MI) in the presence of a left bundle branch block (LBBB) pose a distinctive diagnostic dilemma for physicians. Diagnosing MI through electrocardiogram (ECG) is particularly challenging with LBBB due to the altered ventricular depolarization, resulting in characteristic ECG changes. The delayed left ventricular activation in LBBB, with initial septal activation occurring from right to left (in contrast to the normal pattern), results in the absence of septal Q waves that may suggest the presence of MI. Furthermore, the secondary ST-T wave abnormalities associated with LBBB complicate the identification of injury currents in ischemia and infarction. The Sgarbossa criteria were initially introduced over two decades ago to enhance the diagnostic precision for MI in the setting of LBBB; subsequent modifications by others have aimed to improve sensitivity. This criteria is widely accepted as one of the most valuable tools to assist in the diagnosis of MI when LBBB is present. 

Before delving into the criteria, let's clarify the concept of concordance and discordance in simple words.

  • Concordance means that the QRS complex and the ST changes are moving in the same direction, either both predominantly positive or both predominantly negative.
  • Discordance means that the QRS complex and the ST changes are moving in the opposite direction (e.g. If the QRS is predominantly negative the ST changes will be positive or above the isoelectric line and vice versa). 

If the above is challenging to comprehend, take this home:

  • Concordance = Same direction 
  • Discordance = Opposite direction

Normally (in the setting of LBBB pattern), in leads where the QRS complex is usually a positive deflection, the ST-segment should be slightly below the isoelectric line. Conversely, in leads where the QRS is negative, especially in V1-V3, the ST-segment should rise slightly above the isoelectric line, and this is termed appropriate discordance. 

BUT, when the ECG shows inappropriate concordance (ST segment elevation in positive leads, and ST segment depression in negative leads), there is a HIGH percentage of acute MI.  

Well, I think you are in the position to get into the matter. The following criteria can be used to diagnose acute myocardial infarction in the presence of the LBBB pattern:

Sgarbossa's Criteria (by Sgarbossa et al. 1996)

  • Concordant ST-segment elevation ≥1 mm for leads with a predominantly positive QRS complex—score of 5.
  • Concordant ST-segment depression ≥1 mm in leads V1, V2 or V3—score of 3.
  • Excessively discordant ST-segment elevation ≥5 mm in leads with negative QRS complexes—score of 2.

Modified Sgarbossa Criteria (by Stephen W. Smith et al. 2012)

  • ≥ 1 lead with ≥1 mm of concordant ST elevation.
  • ≥ 1 lead of V1-V3 with ≥ 1 mm of concordant ST depression.
  • 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.

Barcelona Criteria (by Andrea Di Marco et al. 2020)

  • Concordant ST segment depression in any lead.
  • ST deviation ≥1 mm (0.1 mV) discordant with the QRS, in leads with max (R|S) voltage (the voltage of the largest deflection of the QRS, ie, R or S wave) ≤6 mm (0.6 mV).

*Regarding diagnostic accuracy and sensitivity-specificity for each criteria, please consult the references.

Here you can see a classic example with graphic explanations that will facilitate understanding.

EKG tracings are generated by exclusive EKGDX technology. Courtesy of EKGDX

 

EKG tracings are generated by exclusive EKGDX technology. Illustration courtesy of Dr. Roig

 

Here are few examples of acute myocardial infarction in the setting of LBBB. Take a look and apply what you have learned.

Can you see concordant ST segment elevation? Can you see excessively discordant ST-segment elevation? Courtesy of ECG Medical Training

`

Ask you the same questions. Courtesy of @syamkumarmd (Twitter)

 

Red circle shows concordant ST segment elevation. Courtesy of Dr. Carlos Pineda from ECG Weekly

Who or what is Sgarbossa?

Elena Sgarbossa, MD (Twitter profile picture)

Elena B. Sgarbossa, MD, is an American cardiologist, author, and medical translator, originally from Argentina. She serves as a member of the Editorial Board of the Journal of Electrocardiology. Dr. Sgarbossa is renowned for creating and validating a clinical prediction rule utilizing an electrocardiogram criteria to diagnose acute myocardial infarction in individuals experiencing chest pain and left bundle branch block. The Sgarbossa Criteria were initially introduced in 1996. She and the team used data from the famous GUSTO-1 trial (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries). 

Courtesy of Elena Sgarbossa, MD (from Twitter)

It's a real pleasure. Courtesy of Dr. Roig (from Twitter) 

Important

  • Sgarbossa criteria was a game changer. 
  • Subsequent modifications by other authors have aimed to improve sensitivity. You must study all of them.
  • You can’t rule out an acute myocardial infarction if the criteria are absent.

WELL, that's it for today's article. I hope it has been useful to you. If you have a friend or colleague who has asked you about this topic, send them this article. See you at the next one.

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References 

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Thanks for reading this blog.

Dr. Roig

Sgarbossa Criteria. Concordance vs Discordance.