This is the conclusion to 88 year old male CC: Chest pain.
Let's take another look at the 12-lead ECG.
This ECG shows acute STEMI in the presence of left bundle branch block.
It's also an excellent example of the value of using "excessive discordance" to identify acute STEMI in the presence of left bundle branch block.
For a more extensive discussion of this topic see:
First, let's see if we can make the case for acute STEMI using Sgarbossa's original criteria.
As a refresher, here are Sgarbossa's criteria to identify AMI in the presence of LBBB
1.) ≥ 1 mm of concordant ST-elevation (in the same direction as the majority of the QRS complex) in at least one lead
2.) ≥ 1 mm of ST-depression in lead V1, V2 or V3
3.) ≥ 5 mm of discordant ST-elevation (opposite the majority of the QRS complex) in at least one lead
According to the original scoring algorithm, the more of these criteria that are met, the higher the probability of AMI.
So, let's apply these criteria to this case.
Do we see ST-elevation that is concordant with the majority of the QRS complex in at least one lead?
This criterion appears to be met in lead II.
Do we see ST-depression in leads V1, V2 or V3?
Possibly. I bring up data quality so often on this blog that I probably sound like a broken record, but it's rare that I run a case study where we don't have to compensate for poor data quality in one way or another. In this case it appears that ST-depression may be present in lead V1.
How about discordant ST-elevation = or > 5 mm?
This finding is absent on this 12-lead ECG. However, it doesn't really matter because this finding is (by far) the least specific of Sgarbossa's criteria. It's the least specific because it doesn't take into account the depth of the S-wave (rule of proportionality).
In other words, the deeper the S-wave, the greater the ST-elevation, and this is normal.
That's why we use the modified criterion proposed by Stephen Smith, M.D. (Dr. Smith's ECG Blog).
Rather than look for ST-elevation that is = or > 5 mm, we look for ST-elevation that is > than 0.2 (or 1/5) the depth of the S-wave!
To put this in a quick "rule of thumb" for you, for every 5 mm of S-wave depth, we allow 1 mm of ST-elevation.
Or, you can break out the calipers and calculate the ST/QRS ratio.
Let's apply the modified criterion to this case.
Do we see any leads with a ST/QRS ratio > 0.2?
We certainly do (and it's not even close).
So, lead II meets one of Sgarbossa's original criteria (concordant ST-elevation = or > 1 mm) while leads III and aVF meet Smith's modified criterion (ST/QRS ratio > 0.2).
This is more than enough evidence to call this an acute inferior STEMI in the presence of LBBB.
But we aren't finished yet!
Smith et al. discovered that "excessive discordance" works for positive and negative QRS complexes!
With this in mind, do we see "excessive discordance" anywhere else in this ECG?
Yes we do! Lead aVL shows ST-depression that is "excessively discordant" with the QRS complex.
Is lead aVL reciprocal to leads II, III and aVF?
Yes it is.
Point, game and match.
BTW, I also made the calculations for lead V4 because it looked close to me.
It was close, but no cigar. So take a good look at lead V4! This shows close to the maximum ST-elevation that is permitted for a QRS complex of this size.
Once you train your eye it's much easier to spot excessive discordance!