Right Bundle Branch Block



  • In RBBB, activation of the right ventricle is delayed as depolarisation has to spread across the septum from the left ventricle.
  • The left ventricle is activated normally, meaning that the early part of the QRS complex is unchanged.
  • The delayed right ventricular activation produces a secondary R wave (R’) in the right precordial leads (V1-3) and a wide, slurred S wave in the lateral leads.
  • Delayed activation of the right ventricle also gives rise to secondary repolarization abnormalities, with ST depression and T wave inversion in the right precordial leads.
  • In isolated RBBB the cardiac axis is unchanged, as left ventricular activation proceeds normally via the left bundle branch.

Tall R' wave in V1 ("M" pattern) with wide, slurred S wave in V6 ("W" pattern)

ECG changes in RBBB

Diagnostic Criteria

  • Broad QRS > 120 ms
  • RSR’ pattern in V1-3 (‘M-shaped’ QRS complex)
  • Wide, slurred S wave in the lateral leads (I, aVL, V5-6)

Associated Features

  • ST depression and T wave inversion in the right precordial leads (V1-3)


  • Sometimes rather than an RSR’ pattern in V1, there may be a broad monophasic R wave or a qR complex.

Typical RSR' pattern ('M'-shaped QRS) in V1

Wide slurred S wave in lead I

Typical pattern of T-wave inversion in V1-3 with RBBB

Causes of RBBB

  • Right ventricular hypertrophy / cor pulmonale
  • Pulmonary embolus
  • Ischaemic heart disease
  • Rheumatic heart disease
  • Myocarditis or cardiomyopathy
  • Degenerative disease of the conduction system
  • Congenital heart disease (e.g. atrial septal defect)

More ECG Examples of RBBB

Example 1

Right Bundle Branch Block


Example 2


Example 3


Incomplete RBBB

  • Incomplete RBBB is defined as an RSR’ pattern in V1-3 with QRS duration < 120ms.
  • It is a normal variant, commonly seen in children (of no clinical significance).

Incomplete RBBB (RSR' pattern in V1) in a 2-year old child


Differential Diagnosis of RBBB

  • An RSR’ pattern in V1-3 may also be caused by Brugada syndrome — an ECG pattern associated with malignant ventricular arrhythmias.

Brugada syndrome


Related Topics

Author Credits

Further Reading


  • Da Costa D, Brady WJ, Edhouse J. Bradycardias and atrioventricular conduction block. BMJ. 2002 Mar 2;324(7336):535-8. Review. PMID: 11872557. Full text.
  • Hampton, JR. The ECG in Practice (5th edition), Churchill Livingstone 2008.
  • Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice (6th edition), Saunders 2008.
  • Wagner, GS. Marriott’s Practical Electrocardiography (11th edition), Lippincott Williams & Wilkins 2007.
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