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).

Electrophysiology

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

RBBB with LAFB.

  • 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
OMI ECG Proximal LAD RBBB

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.


Advanced Reading

Online

Textbooks


LITFL Further Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

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) 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

2 Comments

  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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