NOTE: The Easy-Link to my 17-minute ECG Video-2 on the "Bundle Branch Blocks" is at: - 
  • Information about this Video is on my ECG Blog #96 -
  • To facilitate using this 17-minute video  I have made a timed CONTENTS. Fast Forward at the above YouTube LINK to focus in on the specific subject area you are looking for!
  • Your Feedback is welcome!  Write Me at 
TIMED CONTENTS (Click on Links to Fast Forward! ):
0:00 – Introduction (How to contact me).
1:34 – Normal conduction vs BBB (conduction is slowed).
2:19 – How do we define “Wide” for the QRS.
3:16 – Overview Algorithm for BBB Diagnosis in <5 Seconds.
4:45 – ECG Diagnosis of RBBB (criteria).
5:50 – ECG Diagnosis of LBBB (criteria).
7:13 – Criteria for IVCD (IntraVentricular Conduction Defect).
8:40 – Expected ST-T Wave Changes with BBB.
10:20 – RBBB “Equivalent” Patterns in Lead V1.
11:28 – PRACTICE Tracings: What Type of BBB?
12:44 – Practice Schematic showing a RBBB“ Equivalent” Pattern.
13:28 – Practice Schematic showing Primary ST-T Wave Changes.
14:22 – Practice Schematic showing IVCD.
15:09 – Practice Schematic showing LBBB.
15:51 – Practice (Real Tracing) – Why is the QRS Wide? (IVCD).


  1. In which situation does we see S wave only in V6 , , despite monophasic R wave in lead I , QRS complex wide (120 ms) and QS in V1 ? does it represent LBBB or IVCD ?
    and can we apply sgarbosa criteria
    This example confusing me

    1. Hello Mostafa. I will answer your Question by referring you to this link — — which provides download of a 31-page pdf (excerpted from my ECG-2014-ePub) — in which I review ECG diagnosis of the Bundle Branch Blocks. Discussion on ECG Diagnosis of BBB + Acute MI begins with Section 05.24, but I recommend that you read the Sections before this. After you review this Section — I think the approach to Sgarbossa criteria will make more sense to you. Many of the points at the link you provide are quite subtle and advanced, and my approach may be more direct and a bit easier to follow, yet still as accurate.

      As to the specifics of your question — I would have to see an actual tracing to know for any given case as to whether a tracing might best be classified as "LBBB" vs "IVCD" — and there ARE some tracings, where EITHER classification may be valid ... I discuss this in the 31-page pdf I suggested that you download. I hope that helps — :)

  2. please sir , why in above link i provided , as per Tom Bouthillet (cannot trust the ST/T complex in the lead above the transition) in LBBB
    according to you link , it considered concordance ST/T in V5, but does it affect whether transition point

  3. Hello Mostafa. As your question relates more to the post by Tom Bouthillet — I have just written an extensive Comment on Tom's excellent post. My approach in the above ECG Video ( — simplifies assessment by focus on the 3 Key Leads (I, V1, V6). In doing so — rapid assessment of conduction defects is possible without having to worry about what is happening around the area of transition. As a more advanced concept — I always look at the other 9 leads, but I agree with the point emphasized by Tom on his post that assessment of ST-T wave changes is less reliable with conduction defects in the leads close to the area of transition (in which the QRS changes from being predominantly negative to predominantly positive).

  4. Does RBBB equivalent ( qR,QR in V1) is normal variant of RBBB, or its due to RBBB+septal MI.
    I know that there should not be any Q in V1-V3

    1. Thanks for your comment Hasan. As is often the case — I'd need to see the actual ECG in order to know what I'd call for a given tracing. But, in an adult with a history consistent with possible coronary disease — the finding of RBBB with definite Q wave in V1 or V2 should at least suggest the possibility that there may have been prior anteroseptal infarction.