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Rhythm

Right bundle branch block

Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

In right bundle branch block, activation of the right ventricle is delayed, producing a wide QRS with a terminal rsR’ pattern in the right precordial leads and a wide S wave in the lateral leads. It may be a normal variant or a sign of right heart disease.

ECG criteria

  • QRS duration 120 ms or more (complete RBBB); the same morphology with a QRS under 120 ms is incomplete RBBB.
  • rsR’ (M-shaped) or broad notched R in V1-V2, with R’ taller than the initial r.
  • Wide, slurred S wave in I, aVL and V5-V6.
  • Secondary ST depression and T inversion in V1-V3.
  • Normal initial septal activation, so the early QRS forces are unchanged; axis is usually normal.

Mechanism

Block in the right bundle branch lets the septum and left ventricle depolarise normally through the left bundle, while the right ventricle is activated late by cell-to-cell spread. The delayed rightward forces appear as the terminal R’ in V1 and the broad terminal S in the left-sided leads.

Common causes

  • Normal variant (incomplete or complete) in otherwise healthy people.
  • Right ventricular strain or enlargement: pulmonary embolism, pulmonary hypertension, cor pulmonale.
  • Congenital heart disease, especially atrial septal defect; Brugada pattern needs distinction.
  • Ischaemic heart disease, cardiomyopathy, myocarditis, degenerative conduction disease, cardiac surgery.

Management principles

Isolated RBBB in an asymptomatic person usually needs no specific treatment. Look for underlying cardiac or pulmonary disease, particularly if the block is new or associated with syncope, and follow local guidelines for further evaluation.

High-level principles for study. Treatment decisions follow local guidelines and the clinical situation.

Pitfalls and mimics

  • A new RBBB with right ventricular strain features (S1Q3T3, T inversion in V1-V3) should prompt consideration of pulmonary embolism.
  • Persistent ST elevation in V1-V2 in a coved or saddleback pattern with RBBB-like QRS may be Brugada pattern, not simple RBBB.
  • RBBB does not hide ST changes of acute infarction as LBBB does, but the secondary ST-T changes in V1-V3 can be mistaken for ischaemia.

Practise in the ECG trainer — Recognise this pattern on generated tracings.

References

  1. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram, Parts I to VI. American Heart Association / American College of Cardiology Foundation / Heart Rhythm Society (2009) — Tier 2 (guidelines / primary literature)
  2. Wagner GS, Strauss DG. Marriott's Practical Electrocardiography. Wolters Kluwer, 12th edition (2013) — Tier 3 (textbook)
  3. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. Elsevier, 12th edition (2022) — Tier 3 (textbook)

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