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


  • VinceD says:

    That last ECG looks just like what Dr. Mattu talks about here:

    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.

  • 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.

  • Tom B says:

    You just drive and ambulance but you read Garcia and Holtz and you know Dr. Smith’s views on concordance! HAHAHA! 🙂

  • Christopher says:

    Gotta have something to read if your system is on SSM 🙂

  • andrew says:

    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

  • Tom B says:

    Andrew –

    Yes! Or, in the presence of LBBB, with “excessive discordance” in the anterior leads.


  • Pete says:

    if you look closely most of the qrs complexes are only 2 boxes wide 0.08 not 0.12 there is numerous st depressions in multiple leads and avr st elevation which again would lead to lmca occlusion or proximal lad occlusion was there trops done was he ill old ecg's and why was the machine on 150 hz 40hz gives you less interference especially in limb leads

  • Pete says:

    andrew yes as tom says we would also expect reciprocal st depression inferiorly

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