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

Causes of Right Bundle Branch Block (RBBB)

RBBB results from interruption of conduction through the right bundle branch, with etiologies spanning structural heart disease, congenital conditions, infiltrative processes, infections, degenerative changes, and acute conditions like pulmonary embolism. 1

Pathophysiologic Categories

The American College of Cardiology classifies RBBB causes as developmental, hereditary/genetic, metabolic, infectious, inflammatory, infiltrative, traumatic, ischemic, malignant, or degenerative in nature. 1

Structural and Ischemic Heart Disease

• Ischemic heart disease, particularly anterior infarction with persistent intraventricular conduction disturbances, carries an unfavorable prognosis. 1
• Hypertensive heart disease is a recognized structural cause of RBBB. 1
• Cardiomyopathies of various types can produce RBBB, occurring either as part of the disease process or as primary degenerative lesions of the specialized conducting tissue, particularly in older individuals. 1

Congenital Heart Disease

• Unoperated and operated congenital heart disease, including atrial septal defects, commonly present with RBBB. 1
• Ebstein's anomaly of the tricuspid valve can display prolonged PR interval and wide RBBB. 1
• Congenital isolated complete RBBB is very rare in neonates. 1
• Heart transplant recipients develop RBBB as the most common electrocardiographic abnormality, with prevalence increasing over time post-transplantation (8% at mean 1.8 years, 20% at mean 5.6 years), though the prognosis is benign. 2

Genetic and Channelopathies

• 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
• Arrhythmogenic right ventricular cardiomyopathy shows localized QRS prolongation in right precordial leads (V1-V3) with epsilon waves and requires specialized evaluation when RBBB occurs with symptoms suggesting this diagnosis (family history of sudden death, ventricular arrhythmias). 1

Infiltrative and Inflammatory Processes

• Sarcoidosis can cause RBBB through infiltration of the conduction system. 1
• Cardiac tumors may produce RBBB through direct involvement of the right bundle branch. 1
• Myocarditis represents an infectious/inflammatory cause of RBBB. 1
• Chagas' disease is a specific infectious etiology for RBBB. 1

Acute Conditions

• Acute pulmonary embolism, particularly massive trunk obstruction, can cause transient or new-onset RBBB as a marker of acute right ventricular overload. 3, 4, 5
• RBBB with a QR pattern in V1 has high positive predictive value for cardiac arrest caused by high-risk pulmonary embolism and may warrant thrombolytic therapy even before CTPA confirmation. 4
• In massive pulmonary trunk embolism, 80% of patients develop newly emerged RBBB on ECG. 5

Degenerative and Idiopathic

• Primary degenerative lesions of specialized conducting tissue occur as an isolated phenomenon, particularly in older individuals. 1
• Isolated RBBB in asymptomatic young athletes (prevalence <2%) may represent idiopathic, clinically benign conduction delay, though follow-up is warranted. 1

Critical Clinical Pitfalls

• Always evaluate for structural heart disease with transthoracic echocardiography in newly detected RBBB cases, particularly when associated with other conduction abnormalities. 1
• Assess for symptoms including syncope, presyncope, dizziness, fatigue, or exercise intolerance in all patients with RBBB. 1
• RBBB pattern with ST-elevation in V1-V3 represents Brugada pattern and requires immediate specialized evaluation due to sudden cardiac death risk. 1
• Bifascicular block (RBBB with left anterior or posterior hemiblock) carries increased risk of progression to complete AV block and requires closer monitoring. 1, 6
• Family history of sudden cardiac death warrants genetic evaluation. 1
• Complete RBBB is uncommon in healthy individuals (<2% in athletes, 0.6% in males <40 years) and should prompt investigation for underlying cardiovascular disease. 1