This is a follow-up discussion to an usual case of left bundle branch block (60 year old male CC: Shortness of breath).
Let’s take another look at the 12-lead ECG.
It turns out this patient was experiencing a STEMI.
However, the 12-lead ECG doesn’t meet any of the typical criteria for acute STEMI in the presence of left bundle branch block (if indeed this is a left bundle branch block).
While it’s a supraventricular rhythm with a QRS duration > 120 ms and shows LBBB morphology in lead V1, there are S-waves in leads I and V6. Hence, you could argue that this is a nonspecific intraventricular conduction defect.
Having said that, there is something strange about the ST-segments in this ECG.
Normally when faced with a left bundle branch block I consider the “rule of T-wave discordance”.
With a left bundle branch block, that means that the T-wave (and ST-segment) should be deflected opposite the QRS complex.
But what about qR, rS or Rs complexes in the presence of left bundle branch block?
Should the ST/T-wave be deflected opposite the majority of the QRS complex or the terminal deflection?
Opinions are divided on this point but I use the terminal deflection.
Let’s look at lead aVR for this case.
You will note that the ST-segment and T-wave are deflected in the same direction as the terminal deflection of the QRS complex. That makes it concordant (bad).
Now let’s look at the inferior leads.
I would consider this to be concordant ST-depression.
How let’s look at leads V5 and V6.
Even though these are RS complexes and almost equiphasic, the ST-depression is in the same direction as the terminal deflection. Again, I would consider this to be concordant (bad).
So, we have ST-elevation in lead aVR and ST-depression in the inferior and lateral leads.
There also appears to be less ST-elevation than we would normally expect in the right precordial leads, but it’s hard to say definitively due to the wandering baseline and the fact that the S-waves are “cut off” in leads V2 and V3.
It reminds me a little bit of the previous case 63 year old male CC: Chest pain.
Let’s take a look at that 12-lead ECG.
Here the QRS duration is only 116 ms (not quite a bundle branch block) but there is ST-elevation in lead aVR and ST-depression in the inferior, lateral and anterior leads.
The patient was experiencing an acute left main coronary occlusion.
Again, this was a tough case, and I can’t say that it was diagnostic for acute STEMI, but it wasn’t “normal” looking either.
58 year old female CC: Chest pain (Sgarbossa’s criteria)
62 year old male CC: Chest pain (LBBB with ST-elevation > 0.2 the QRS complex)