What is a right bundle branch block (RBBB)?

Right Bundle Branch Block (RBBB): Definition and Characteristics

Right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system, characterized by QRS duration ≥120 ms in adults, an rSR' pattern in leads V1-V2, and S waves of greater duration than R waves in leads I and V6. 1, 2

Diagnostic ECG Criteria for Complete RBBB

• QRS duration ≥120 ms in adults (>100 ms in children 4-16 years, >90 ms in children <4 years) 2
• rSR', rsR', or rSR pattern in leads V1 or V2, with the R' deflection usually wider than the initial R wave 2
• S wave of greater duration than R wave or >40 ms in leads I and V6 2, 3
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 2
• Often accompanied by ST depression and T wave inversion in right precordial leads (V1-V2) 3

Pathophysiology

• RBBB occurs when conduction is delayed or blocked in the right bundle branch of the His-Purkinje system 1
• The normal conduction axis consists of the sinus node, atrial muscle, atrioventricular node, His bundle, bundle branches, fascicles, Purkinje fibers, and ventricular muscle 1
• When the right bundle branch is blocked, the right ventricle is activated by impulses traveling through the left bundle branch and then crossing the interventricular septum, causing delayed right ventricular activation 3

Epidemiology and Clinical Significance

• Complete RBBB has a prevalence of approximately 1% in the general population 2
• In young adult athletes, the prevalence ranges from 0.5% to 2.5% 2
• RBBB may be an isolated and clinically benign finding or associated with underlying cardiovascular disorders 2
• RBBB is commonly seen after repair of tetralogy of Fallot and in Ebstein's anomaly 2

Distinguishing Features from Other Conditions

• Incomplete RBBB has a QRS duration between 110-120 ms in adults 2, 4
• RBBB must be differentiated from Brugada syndrome, which can have similar ECG patterns but is associated with a family history of sudden death 3
• RBBB should be distinguished from right ventricular enlargement, arrhythmogenic right ventricular cardiomyopathy, and ventricular pre-excitation 4

Clinical Evaluation

• In patients with newly detected RBBB, a transthoracic echocardiogram is reasonable if structural heart disease is suspected 1
• In symptomatic patients with conduction system disease where atrioventricular block is suspected, ambulatory electrocardiographic monitoring is useful 1
• The European Society of Cardiology recommends that demonstration of complete bundle branch block should lead to a cardiological work-up including exercise testing, 24-hour ECG monitoring, and imaging 2

Prognostic Implications

• The prognosis of RBBB in the absence of underlying cardiac disease is generally good 3
• RBBB may have hemodynamic consequences in cardiac failure with associated asynchrony of the left ventricle or in certain cases of right ventricular dilatation encountered in congenital heart disease 3
• The progression of RBBB to complete atrioventricular block is rare in the absence of associated cardiac disease 3
• In heart transplant recipients, RBBB is common but does not appear to be associated with increased mortality or sudden cardiac death 5

Special Considerations

• Preexisting RBBB does not invalidate interpretation of the exercise ECG, except in the anterior precordial leads (V1, V2, and V3) 1
• RBBB has been associated with underlying coronary artery disease, particularly with obstructive disease affecting the left anterior descending artery, though this association has been questioned 1
• RBBB can be induced by catheter manipulation during cardiac procedures (catheter-induced RBBB), which is typically transient 6