The differences between RBBB and LBBB in ECG are more simple than you imagine!. Just follow two simple steps:
- QRS duration greater than or equal to 120 ms in adults (>0.12 sec or >3 small boxes), greater than 100 ms in children 4 to 16 years of age, and greater than 90 ms in children less than 4 years of age.
- Look I, V1 and V6
Left Bundle Branch Block (LBBB): Dominant S wave in V1 with broad, notched (‘M’-shaped) R wave in V6
Right Bundle Branch Block (RBBB): Tall R’ wave in V1 (“M” pattern) with wide, slurred S wave in V6 (“W” pattern)