Right Bundle Branch Block (RBBB)

ECG Diagnostic criteria

  • QRS duration > 120ms
  • RSR’ pattern in V1-3 (“M-shaped” QRS complex)
  • Wide, slurred S wave in lateral leads (I, aVL, V5-6)
Right-Bundle-Branch-Block-RBBB ECG-Strip LITFL
RBBB: Right Bundle Branch Block
V1: RSR’ pattern in V1, with (appropriate) discordant T wave changes
V6: Widened, slurred S wave in V6

Associated features incude:

  • Appropriate discordance with ST depression and/or T-wave inversion in right precordial leads (V1-3).


In normal cardiac conduction, impulses travel equally down the left and right bundles, with the septum activated from left to right and the formation of small Q waves in lateral leads

  • In RBBB, the left ventricle is activated normally, thus the early part of the QRS complex correlating to septal depolarisation is unchanged
  • There is delayed activation of the right ventricle as depolarisation originates from the left ventricle across the septum. This produces a secondary R wave (R’) in the precordial leads, and a wide, slurred S wave in lateral leads
  • Normal activation of the left ventricle means that cardiac axis remains normal in isolated RBBB
Sequence of conduction in RBBB:
1) Left ventricular activation via the left bundle (black arrow) occurs normally
2) Septal depolarisation (yellow arrows) is thus unaffected, producing a normal early QRS complex
3) Activation of the RV originates across the septum. The resultant depolarisation vector (red arrow) produces delayed R waves in leads V1-3, and S waves in lateral leads

ECG QRS Morphology

QRS Morphology in V1

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

ECG Right Bundle Branch Block RBBB V1 RSR Complex
Typical RSR’ pattern (‘M’-shaped QRS) in V1

QRS Morphology in Lateral Leads
ECG Right Bundle Branch Block RBBB Lead I wide S
Wide slurred S wave in lead I

Appropriate discordance
  • Appropriate discordance refers to the fact that abnormal depolarisation should be followed by abnormal repolarisation, which appears discordant to the preceding QRS complex
  • In RBBB, this manifests as ST depression and/or T-wave inversion in leads V1-3
ECG Right Bundle Branch Block RBBB T wave inversion
Appropriate discordance: Typical pattern of T-wave inversion in V1-3 with RBBB

Causes of Right Bundle Branch Block

There is increasing literature suggesting that in the context of chest pain, a new RBBB is highly concerning for OMI and a potential indication for immediate reperfusion therapy. The right bundle branch is supplied by LAD perforators in most patient populations and thus occlusion of this branch may manifest as a new RBBB +/- LAFB.

ECG Examples of Right Bundle Branch Block
Example 1
ECG Right Bundle Branch Block RBBB 6


  • Broad QRS > 120ms
  • Note the prominent delayed RV conduction, manifested as a tall, broad R wave (R’) best seen in lead V1
  • Widened S wave is best appreciated in lead I
  • There is appropriate discordance in the right precordial leads with T-wave inversion

Example 2
ECG Right Bundle Branch Block RBBB 5

Isolated RBBB.

  • Typical RSR’ pattern in V1-2
  • Widened S waves again demonstrated in lateral leads, especially V4-6
  • Appropriate discordance in leads V1-2

Example 3
ECG Right Bundle Branch Block RBBB 3

Isolated RBBB.

  • RSR’ pattern in V1-3
  • Lateral S wave changed are not evident here
  • Note note normal axis in isolated RBBB

Example 4

RBBB with LAFB in the context of chest pain.

  • RBBB is seen with RSR’ pattern in V1-3 and slurred S waves in lateral leads
  • There is concordant ST segment changes best seen in V2, and hyper-acute T waves inferiorly. This patient was found to have a 99% proximal LAD occlusion. See OMI: Replacing the STEMI misnomer for further case details

Incomplete RBBB
ECG Incomplete RBBB Normal Pediatric 2 year old
  • 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).

Differential Diagnosis of RBBB
ECG Brugada Tyope 1 RBBB mimic 2
  • An RSR’ pattern in V1-3 may also be caused by Brugada syndrome — an ECG pattern associated with malignant ventricular arrhythmias.

Further reading

Advanced Reading



LITFL Further Reading



Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner


  1. Quick question for clarification: For a it to be classified as an RSR pattern the S wave needs to be a negative deflection below the isoelectric line right?

    So how can the ecg example under “variations” be called a RSR pattern. Isnt it more indicative of a rR pattern?

    Keep up the good work – you guys are lifesavers

  2. How about in rsR’ where r wave is greater than the R” wave (Lead V1 and V2). opposite above. is it still called RBBB

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