What causes a right bundle branch block?

What Causes Right Bundle Branch Block

Right bundle branch block results from interruption of conduction through the right bundle branch, with causes ranging from benign idiopathic conduction delay to serious underlying cardiovascular disease including ischemic heart disease, cardiomyopathies, congenital heart disease, and infiltrative processes. 1

Pathophysiologic Mechanisms

RBBB represents delayed activation of the right ventricle due to conduction interruption through the right bundle branch, manifesting as QRS duration >120 ms on ECG. 1 The underlying pathophysiology can be:

• Developmental 1
• Hereditary/genetic 1
• Metabolic 1
• Infectious 1
• Inflammatory 1
• Infiltrative 1
• Traumatic 1
• Ischemic 1
• Malignant 1
• Degenerative 1

The block can be either static or progressive in nature, with varying degrees of conduction delay. 1

Specific Etiologies by Category

Structural Heart Disease

• Ischemic heart disease, particularly anterior myocardial infarction with persistent intraventricular conduction disturbances, carries an unfavorable prognosis. 1
• Hypertensive heart disease is a recognized cause of RBBB. 1
• Cardiomyopathies of various types can produce RBBB. 1

Degenerative and Infiltrative Processes

• Primary degenerative lesions of the specialized conducting tissue can lead to RBBB, particularly in older individuals as an isolated phenomenon. 2, 1
• Sarcoidosis is an infiltrative cause requiring prophylactic pacing even if AV block is transient due to disease progression risk. 2, 1
• Cardiac tumors and other infiltrative processes can cause RBBB. 1
• Amyloidosis may cause RBBB and requires prophylactic pacing consideration. 2

Infectious and Inflammatory Causes

• Myocarditis is an inflammatory cause of RBBB. 1
• Chagas' disease is an infectious cause of RBBB. 1
• Lyme disease can cause AV block during the acute phase, though this typically resolves and does not require permanent pacing. 2

Congenital and Genetic Conditions

• Congenital heart disease, both unoperated and operated (particularly atrial septal defects and after tetralogy of Fallot repair), commonly presents with RBBB. 1, 3
• Ebstein's anomaly of the tricuspid valve displays prolonged PR interval and wide RBBB. 1, 3
• 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 including RBBB in young individuals. 2, 1
• Congenital isolated complete RBBB is very rare in neonates. 1

Other Causes

• Pulmonary embolism, particularly high-risk PE, can cause RBBB with a QR pattern in V1, which has high positive predictive value for cardiac arrest due to PE. 4
• Right ventricular strain and pulmonary hypertension may manifest as incomplete RBBB. 5
• Neuromuscular diseases may cause RBBB and require prophylactic pacing consideration due to progression risk. 2

Epidemiology and Clinical Context

RBBB has a prevalence of approximately 1% in the general population, with 0.6% in males under 40 years. 2, 3 In young adult athletes, prevalence ranges from 0.5% to 2.5%. 3 Complete RBBB is uncommon in healthy individuals and athletes (<2%). 2, 1

Male sex (HR = 3.8) and advancing age (HR = 1.05 per year) are the primary factors associated with development of complete RBBB. 6

Critical Clinical Pitfalls

When RBBB Signals Serious Disease

• Bifascicular block (RBBB with left anterior or posterior hemiblock) carries increased risk of progression to complete AV block and requires comprehensive evaluation. 2, 1
• Alternating bundle branch block (RBBB and LBBB on successive ECGs) indicates severe conduction system disease with rapid progression to complete heart block. 2
• RBBB with symptoms (syncope, presyncope, dizziness, fatigue, exercise intolerance) requires urgent evaluation for arrhythmic etiology. 1
• RBBB with ST-elevation in V1-V3 represents Brugada pattern and requires immediate specialized evaluation due to sudden cardiac death risk. 1
• RBBB with family history of sudden cardiac death warrants genetic evaluation. 1

When RBBB May Be Benign

Isolated RBBB in asymptomatic young athletes may represent idiopathic, clinically benign conduction delay through the right bundle branch, though follow-up is warranted. 2, 1 However, isolated fascicular and bundle branch blocks rarely cause symptoms on their own, but their presence may be a marker for underlying structural heart disease. 1

Mandatory Evaluation

Always evaluate for structural heart disease with transthoracic echocardiography in newly detected cases, particularly when associated with other conduction abnormalities. 1 The European Heart Journal recommends cardiological work-up including exercise testing, 24-hour ECG monitoring, and imaging for all athletes with complete bundle branch block. 2

Before attributing RBBB to chronic causes, exclude reversible etiologies such as electrolyte abnormalities, hypothermia, or perioperative inflammation near the AV junction. 2

Special Diagnostic Considerations

Arrhythmogenic right ventricular cardiomyopathy (ARVC) shows localized QRS prolongation in right precordial leads (V1-V3) with epsilon waves (terminal notch in QRS complex) and should be considered in the differential diagnosis of RBBB, especially with family history of sudden death or ventricular arrhythmias. 2, 1

Incomplete RBBB may reflect right ventricular strain, pulmonary hypertension, or predisposition to atrial fibrillation, and should not be routinely regarded as harmless in high-risk individuals. 5