Bundle Branch Block: Right

Question 1

What diagnostic criteria can be observed on an ECG for RBBB?

Answer 1

• QRS > 0.12s
• ‘RSR’ (“M” shaped) pattern in V1
• Dominant R in V₁
• Inverted T waves in V₁-V₃ or V₄
• Wide slurred S wavw in V₆

Question 2

Briefly describe what can be seen from this ECG of RBBB

Answer 2

V₁: RSR pattern in V₁ (“M” shaped)

V₆: widened slurred S shape

Question 3

Briefly describe the electrophysiology of RBBB

Answer 3

• 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

Question 4

Give examples of causes of RBBB

Answer 4

• Normal variant (isolated RBBB)
• Pulmonary embolism
• Cor pulmonale
• Ischaemic heart disease
• Rheumatic heart disease
• Congenital heart disease (e.g. atrial septal defect)
• Myocarditis
• Cardiomyopathy
• Lenègre-Lev disease: primary degenerative disease (fibrosis) of the conducting system

Question 5

What is the pneumonic to remember RBBB?

Answer 5

WiLLiaM MaRRoW

• WiLLiaM- in LBBB there is a ‘W’ in lead V1 and an ‘M’ wave in lead V6
• MaRRoW- in RBBB there is an ‘M’ wave in lead V1 and a ‘W’ wave in lead V6