Confusion over ECG territories

[Maxilla54]

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I have in my notes:
Anterolateral = I, aVL, V4-6 = LCx
Anteroseptal = V2-4 = LAD
Anterior = V2-6 = LMS

If the LMS branches into LCx and LAD, why are there not changes in a combination of the above i.e. I, aVL, V2-6?

I had an exam q where changes were ST elevation in the V1–V6, I, and aVL leads. I selected Left Main Coronary Artery but the given answer is Left Anterior Descending Artery.
Why am I wrong?

Kind regards

 

[Matthew9Thirtyfive]

I have in my notes:
Anterolateral = I, aVL, V4-6 = LCx
Anteroseptal = V2-4 = LAD
Anterior = V2-6 = LMS

If the LMS branches into LCx and LAD, why are there not changes in a combination of the above i.e. I, aVL, V2-6?

I had an exam q where changes were ST elevation in the V1–V6, I, and aVL leads. I selected Left Main Coronary Artery but the given answer is Left Anterior Descending Artery.
Why am I wrong?

Kind regards

Iirc, LAD can be V1-4 as well as I and aVL. And a left main would have ST elevation in aVR and ST depressions in I, II, and V4-6.

 

[Instatewaiter]

I have in my notes:
Anterolateral = I, aVL, V4-6 = LCx
Anteroseptal = V2-4 = LAD
Anterior = V2-6 = LMS

If the LMS branches into LCx and LAD, why are there not changes in a combination of the above i.e. I, aVL, V2-6?

I had an exam q where changes were ST elevation in the V1–V6, I, and aVL leads. I selected Left Main Coronary Artery but the given answer is Left Anterior Descending Artery.
Why am I wrong?

Kind regards

So lateral wall supplied by lad-diags and lcx.


So it could be either. A prox lad will supply septal v1-2 (septal branches from lad), anterior v3-4 (lad proper) and the lateral wall (diagonals).

 

[Maxilla54]

So lateral wall supplied by lad-diags and lcx.


So it could be either. A prox lad will supply septal v1-2 (septal branches from lad), anterior v3-4 (lad proper) and the lateral wall (diagonals).

Thanks to both for replying!

The basis of my question is - if A supplies B and C. And B supplies territory D and E; C supplies F and G. Then surely blocking A would block off territories D and E and F and G combined?

If LMS supplies LAD and LCx then why are there not elevation is ALL the subterritories?

 

[Instatewaiter]

I would argue it is not a good question.

There may also be something you're missing and not telling us about the question...

 

[Maxilla54]

I would argue it is not a good question.

There may also be something you're missing and not telling us about the question...

13. A 44-year-old man has had a sudden-onset chest pain radiating to his jaw, plus sweating and nausea. An ECG is performed and shows ST elevation in the V1–V6, I, and aVL leads. Which is the single most likely occluded coronary artery? ★
A Left anterior descending artery (LAD)
B Left circumflex coronary artery (LCx)
C Left main coronary artery (LCA)
D Posterior descending artery (PDA)
E Right coronary artery (RCA)

It's a 1 star question so meant to be very easy...
I might be missing something obvious

 

[ChiefsKingdom]

I agree with what was said above about seeing ST elevation in aVR and ST depressions in I, II, and V4-6. Also my guess is that an occlusion in the left main is rare and generally fatal so harder to get an ECG before the patient dies.

 

[Instatewaiter]

I've see 2 LM stemis in the last year. They both survived to discharge . Ekgs Look a lot like a prox LAD stemi.

I would argue the question was not a good one.

St depressions with aVR elevation is usually stenosis in LM. Not occlusion. It is not diagnostic either and there are a handful of things that will cause it including LM, prox lad and mutivessel disease with diffuse ischemia.

 

[Maxilla54]

Thanks for the help everyone! I'll leave the question for now

 

[Dr Alo]

I have an entire lecture series on this topic. But the left main branches, if it's left main disease, you'll see much more ST elevations in many leads. Usually when they say V1-V6 are elevated, they want you to think anterior for boards.

http://DrAlo.tv