Criteria of left bundle branch block
1. QRS > 0.12 sec with mid-slurring.
2. Frontal plane QRS vector variable.
3. V1 rS with upright T wave.
4. V5 and V6 predominantly upright with inverted T.
5. Lead I predominantly upright with inverted T.
Scroll back up to show EKG
[EKG Atlas]
