Diagnostic criteria for right bundle branch block

Just as in the case of left bundle branch block, QRS duration should be 120 ms or more in complete right bundle branch block.

If the duration is less than 120 ms, with RBBB pattern, then it will be called incomplete RBBB, sometimes written as IRBBB. IRBBB pattern could be a normal variant and is often a feature of right ventricular volume overload as in atrial septal defect with large left to right shunt.

rsr’, rsR’ or rSR’ patterns in leads V1 and V2. The terminal R’ wave indicates delayed activation of right ventricle in RBBB.

S waves in leads I and V6  ≥40 ms wide. That also represents delayed activation of right ventricle as seen from left oriented leads.

Normal time to peak R wave in V5 and V6, but >50 ms in V1. That represents delayed activation of right ventricle as noted from right oriented leads in RBBB.