What are the causes of Right Bundle Branch Block (RBBB)?

Causes of Right Bundle Branch Block (RBBB)

Right bundle branch block develops from either primary degenerative lesions of the specialized conducting tissue or from a wide spectrum of cardiac pathologies including ischemic heart disease, cardiomyopathies, myocarditis, infiltrative diseases, congenital heart disease, and channelopathies. 1

Pathophysiologic Framework

RBBB represents interruption of conduction through the right bundle branch, causing delayed right ventricular activation with QRS duration >120 ms. 1 The underlying mechanisms can be categorized as developmental, hereditary/genetic, metabolic, infectious, inflammatory, infiltrative, traumatic, ischemic, malignant, or degenerative in nature. 1

Specific Etiologies by Category

Structural Heart Disease

• Ischemic heart disease, particularly anterior myocardial infarction with persistent intraventricular conduction disturbances, represents a major cause and carries an unfavorable prognosis 1
• Hypertensive heart disease is a well-recognized structural cause 1
• Cardiomyopathies of various types can produce RBBB 2, 3

Degenerative and Infiltrative Processes

• Primary degenerative lesions of the specialized conducting tissue occur as an isolated phenomenon, particularly in older individuals 2, 1
• Sarcoidosis infiltrates the conduction system 1, 3
• Cardiac tumors can mechanically disrupt the right bundle branch 1, 3

Infectious and Inflammatory Causes

• Myocarditis from various infectious agents damages the conduction system 1, 3
• Chagas' disease (Trypanosoma cruzi infection) causes progressive conduction system destruction 1, 3

Congenital Heart Disease

• Ebstein's anomaly of the tricuspid valve characteristically displays prolonged PR interval and wide RBBB 1
• Unoperated and operated congenital heart disease, including atrial septal defects, commonly present with RBBB 2, 3
• Congenital isolated complete RBBB is very rare in neonates 1

Genetic and Hereditary Conditions

• Lenegre disease (progressive cardiac conduction disease) is an autosomal dominant condition linked to SCN5A gene mutations affecting cardiac sodium channels, presenting with various conduction defects in young individuals 2
• Channelopathies affecting ion channel function can produce RBBB 3

Iatrogenic Causes

• Catheter-induced RBBB occurs during right-heart catheterization, electrophysiology studies, or ablation procedures due to mechanical trauma to the endocardial right bundle branch 4
• Post-TAVR (transcatheter aortic valve replacement) procedures show increased RBBB incidence 5

Critical Clinical Pitfalls and Evaluation Strategy

Complete RBBB is uncommon in healthy individuals (<2% in athletes, 0.6% in males <40 years), making it a potential marker of serious underlying cardiovascular disease that mandates thorough investigation. 2

Mandatory Evaluation Steps:

• Always perform transthoracic echocardiography in newly detected RBBB to exclude structural heart disease 1
• Assess for specific symptoms: syncope, presyncope, dizziness, fatigue, or exercise intolerance, which indicate hemodynamically significant disease 1
• Evaluate for bifascicular block (RBBB with left anterior or posterior hemiblock), which carries increased risk of progression to complete AV block and may require pacemaker consideration 1, 3
• Consider exercise testing and 24-hour ECG monitoring when RBBB is detected to assess for underlying structural disease 6

High-Risk Scenarios Requiring Urgent Attention:

• RBBB in the setting of acute myocardial infarction, particularly anterior infarction, indicates extensive myocardial damage and poor prognosis 1
• Alternating bundle branch block (RBBB and LBBB on successive ECGs) indicates severe bilateral conduction system disease with rapid progression to complete heart block 3
• RBBB with symptoms suggesting arrhythmogenic right ventricular cardiomyopathy (family history of sudden death, ventricular arrhythmias) requires specialized evaluation 2

Important Differential Diagnosis:

• Brugada syndrome can mimic RBBB pattern and must be excluded, particularly with personal or family history of sudden death 7
• Arrhythmogenic right ventricular cardiomyopathy shows localized QRS prolongation in right precordial leads (V1-V3) with epsilon waves 2

Benign Variants:

• Isolated RBBB in asymptomatic young athletes may represent idiopathic, clinically benign conduction delay, though follow-up is warranted 2
• Exercise-induced RBBB is rare (0.24% prevalence) and appears benign with age-adjusted hazard ratio of 1.13 for all-cause mortality 8