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1. V1 down
2. I, II, III with RSR’ </aside>

LV polarize via RV myocardium conduction

Signs

• Widened QRS complex (> 120 ms)

• Lateral leads (I, aVF, V5, V6): board, slurred/notched R waves → “bunny ears”, or M, positive deflection

  

• V1, V2: small initial r + large, deep S → (rS, QS)

  

• Lack of Q waves in V5, V6

*LBBB often mask prior MI

*can see ST Depression in leads with positive QRS and ST Elevation in leads with positive

8: Left Bundle Branch Block - ECG Made Simple

• This can look like a MI → the key factor is to see if the QRS duration is normal

ECG

LBBB post MI