The right Bundle Branch doesn’t contribute significantly to Septal Activation. Therefore early part of the QRS complex is unchanged in the right Bundle Branch Block. Left Ventricular activation proceeds normally.

The right ventricule which is located anteriorly and to the right is activated Late and from Left to Right. Therefore terminal forces (Conduction or Depolarization) are directed anteriorly and rightward. In addition, this late Depolarization of right ventricule proceeds by slow muscle to muscle Conduction with variable participation of the right sided specialized Conduction system.

The discordant ST-T wave changes with right Bundle Branch Block are due to activated Left ventricule recover (repolarize) earlier than right Ventricule, So recovery vectors are directed toward the left and away from the right that is why negative deflection of ST-T waves in V1 and positive deflection in V6.

Thus T Wave inversion and Down sloping of ST segment in V1 and V2. #Broad Notched R waves (rSR’ , rsr’ ) in V1 and V2 and Deep S wave in V5 and V6.

The right Bundle Branch Block requires all of the following criteria to be present:

  1. QRS duration equal or more than 0.12 second
  2. Broad notch R waves ( rsr’ rsR’ or rSR’ ) in V1 and V2.
  3. Wide deep S wave in V5 and V6.
  4. T-wave inversion and down sloping ST depression are often seen in leads V1 and V2.

Clinical Significance of the right Bundle Branch Block:

  • The relative fragility of right bundle brunch corresponds to the high prevalence of the right bundle brunch block in general population. In absence of heart disease, it has no prognostic significance.
  • New onset right bundle brunch block predicts higher rate of cardiovascular mortality.
  • Association of RBBB – like pattern with persistent ST segment elevation in the right precordial leads (Brugada syndrome) predicts Ventricular arrhythmias and sudden death.
  • Arrhythmogenic right Ventricular dysplasia may present with right bundle brunch block and /or T Wave inversion in leads V1 – V3.