An unusual case of left bundle branch block – Discussion
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.
EMRAPTV Episode 68: aVR Gets No Respect!
Life in the Fast Lane … Another Widow Maker?
See also:
80 year old male CC: Chest pain
Excessive discordance as a marker of acute STEMI in LBBB
80 year old male CC: Chest pain – Conclusion
58 year old female CC: Chest pain
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)
Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part I
Identifying AMI in the presence of LBBB – Sgarbossa’s Criteria Part II
Categories: ems-topics, patient-management
That last ECG looks just like what Dr. Mattu talks about here: http://www.medscape.com/viewarticle/589781
Although he bounces around a bit in that article and doesn’t provide a cohesive summary, in lectures he succinctly describes left-main occlusion as identifiable by diffuse ST-depression (infero-antero-lateral) with ST-elevation in aVR. The ECG becomes even more specific for left-main disease with concurrent elevation in either aVL or V1 to a lesser degree than aVR. Although you probably can’t get away with calling a STEMI alert for such a patient, it’s worth knowing that it portends a poor prognosis, and may be useful to bring up at the department, knowing it’s not a well known phenomenon (I’ve had a cardiologist tell me it was incorrect and aVR was useless; guess what the patient had…).
One more note: In the presence of tachycardias such as SVT and rapid a-fib, such findings are commonplace and do not correlate with left-main stenosis. They are only applicable when the rate is fairly normal.
by VinceD on Feb 2, 2011 at 6:14 pm
63-year-old male has STE in aVR and near-global STD, criteria for LMCA problem.
as for concordance/discordance, so far opinion’s been divided – garcia and holtz wrote they use terminal deflection, smith uses dominant deflection. me? i just drive an ambulance.
by burnedoutmedic on Feb 2, 2011 at 6:48 pm
You just drive and ambulance but you read Garcia and Holtz and you know Dr. Smith’s views on concordance! HAHAHA!
by Tom B on Feb 2, 2011 at 9:34 pm
Gotta have something to read if your system is on SSM
by Christopher on Feb 3, 2011 at 9:14 am
hey guys im a paramedic student and was wondering how a LAD artery occlusion would present on a 12 lead. would it present with STE in leads v1-v4
by andrew on Feb 3, 2011 at 5:22 pm
Andrew -
Yes! Or, in the presence of LBBB, with “excessive discordance” in the anterior leads.
http://ems12lead.com/2010/12/29/excessive-discordance-as-a-marker-of-acute-stemi-in-lbbb/
Tom
by Tom B on Feb 3, 2011 at 6:31 pm