What are the causes of right bundle branch block (RBBB) in adults?

Causes of Right Bundle Branch Block in Adults

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

Pathophysiologic Framework

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 pathophysiology may be developmental, hereditary/genetic, metabolic, infectious, inflammatory, infiltrative, traumatic, ischemic, malignant, or degenerative in nature. 2

Specific Etiologies by Category

Structural Heart Disease (Most Common in Adults)

• Ischemic heart disease, particularly anterior myocardial infarction with persistent intraventricular conduction disturbances, carries an unfavorable prognosis and is a leading cause. 1, 2 Proximal LAD occlusions affecting septal perforating branches commonly cause RBBB rather than LBBB, as these vessels perfuse the right bundle branch. 3

• Hypertensive heart disease is a recognized cause of RBBB in adults. 1, 2

• Cardiomyopathies of various types can produce RBBB, including dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy. 1, 2

Degenerative and Infiltrative Processes

• Primary degenerative lesions of the specialized conducting tissue occur as an isolated phenomenon, particularly in older individuals, representing age-related fibrosis. 1, 2

• Sarcoidosis is an infiltrative cause requiring prophylactic pacing even if AV block is transient due to disease progression risk. 1

• Amyloidosis may cause RBBB and requires prophylactic pacing consideration. 1

• Cardiac tumors and other infiltrative processes can cause RBBB. 2

Infectious and Inflammatory Causes

• Myocarditis is an inflammatory cause of RBBB. 1, 2

• Chagas' disease is an infectious cause of RBBB. 1, 2

• Lyme disease can cause AV block during the acute phase, though this typically resolves and does not require permanent pacing. 1

Congenital and Genetic Conditions

• Congenital heart disease, both unoperated and operated (particularly atrial septal defects), commonly presents with RBBB. 1, 2

• Ebstein's anomaly of the tricuspid valve displays prolonged PR interval and wide RBBB. 1, 2

• 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. 1, 2

Other Causes

• Neuromuscular diseases may cause RBBB and require prophylactic pacing consideration due to progression risk. 1

• Catheter-induced trauma during right-heart catheterization or electrophysiology procedures can cause transient RBBB due to the endocardial course of the right bundle branch. 4

Epidemiologic Context

RBBB has a prevalence of approximately 1% in the general population, with 0.6% in males under 40 years. 1, 5 In young adult athletes, prevalence ranges from 0.5% to 2.5%. 6, 1 Complete RBBB is uncommon in healthy individuals and athletes (<2%), making its presence a potential marker of serious underlying cardiovascular disease. 1, 5

Critical Clinical Pitfalls: When RBBB Signals Serious Disease

Red Flags Requiring Urgent Evaluation

• RBBB with ST-elevation in V1-V3 represents Brugada pattern and requires immediate specialized evaluation due to sudden cardiac death risk. 1, 5

• Bifascicular block (RBBB with left anterior or posterior hemiblock) carries increased risk of progression to complete AV block and requires comprehensive evaluation. 1, 2, 5

• Alternating bundle branch block (RBBB and LBBB on successive ECGs) indicates severe conduction system disease with rapid progression to complete heart block. 1

• RBBB with symptoms (syncope, presyncope, dizziness, fatigue, exercise intolerance) requires urgent evaluation for arrhythmic etiology. 1, 5

• RBBB with family history of sudden cardiac death warrants genetic evaluation. 1, 5

Specific 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. 1, 2

• Masquerading RBBB occurs with simultaneous high-degree left anterior fascicular block and severe left ventricular enlargement/fibrosis, causing terminal QRS forces to reorient leftward and upward, potentially mimicking LBBB and carrying a poor prognosis due to severe underlying heart disease. 7

Mandatory Evaluation Approach

Always evaluate for structural heart disease with transthoracic echocardiography in newly detected cases, particularly when associated with other conduction abnormalities. 1, 2, 5 The echocardiogram should specifically assess:

• Right ventricular size and function 5
• Evidence of atrial septal defects 5
• Right ventricular pressure and signs of pulmonary hypertension 5
• Associated valvular abnormalities 5
• Left ventricular function and evidence of cardiomyopathy 5

For athletes with complete bundle branch block, cardiological work-up should include exercise testing, 24-hour ECG monitoring, and imaging. 1 Consider cardiac MRI for superior detection of apical HCM, localized LVH, ARVC with predominant left ventricular involvement, and myocarditis. 6