What causes right bundle branch block (RBBB)?

Causes of Right Bundle Branch Block

Right bundle branch block (RBBB) develops from multiple etiologies including primary degenerative lesions of the specialized conducting tissue, ischemic or hypertensive heart disease, cardiomyopathies, myocarditis, channelopathies, cardiac tumors, sarcoidosis, Chagas' disease, and congenital heart disease. 1

Primary Pathophysiologic Mechanisms

RBBB represents interruption of conduction through the right bundle branch, causing delayed activation of the right ventricle with QRS duration >120 ms for complete block. 1 The pathophysiology may be:

• Developmental, hereditary/genetic, metabolic, infectious, inflammatory, infiltrative, traumatic, ischemic, malignant, or degenerative 2
• Characterized as either static or progressive in nature 2

Specific Etiologies by Category

Structural Heart Disease

• Ischemic heart disease: In acute myocardial infarction, particularly anterior infarction with persistent intraventricular conduction disturbances carries unfavorable prognosis 2
• Cardiomyopathies: Familial cardiomyopathy with fibrofatty replacement of the right ventricular free wall and sclerotic interruption of the right bundle branch has been documented 3
• Right ventricular abnormalities: Right ventricular dilation, myocardial atrophy with adipose replacement, and structural right ventricular abnormalities on echocardiography 3
• Hypertensive heart disease 1

Degenerative and Infiltrative Processes

• Primary degenerative lesions of specialized conducting tissue 1
• Sarcoidosis 1
• Cardiac tumors 1

Infectious and Inflammatory

• Myocarditis 1
• Chagas' disease 1

Congenital Conditions

• Congenital heart disease: Ebstein's anomaly of the tricuspid valve classically displays prolonged PR interval and wide RBBB 2
• Atrial septal defect (ostium secundum): RBBB is a common finding, requiring particular attention to splitting of the second heart sound 4
• Congenital isolated complete RBBB is very rare in neonates 2

Channelopathies

• Brugada syndrome: Type-2 Brugada ECG pattern must be differentiated from IRBBB 4
• Arrhythmogenic right ventricular cardiomyopathy 4

Other Causes

• Pulmonary embolism: High-risk PE can present with RBBB, particularly with QR pattern in V1 5
• Hyperkalemia 4
• Ventricular preexcitation (Wolff-Parkinson-White syndrome) 4

Benign Variants

• Athletes: RBBB occurs in <2% of athletes and may be benign in the absence of symptoms, family history, or structural heart disease 1, 6
• Crista supraventricularis (CSV) pattern: RSR' pattern with QRS width <100 ms may result from posterior apex deviation, subpulmonic area delay, or late CSV activation 4
• Technical factors: Higher placement of electrodes V1 and V2, pectus excavatum 4

Clinical Pitfalls

Isolated fascicular and bundle branch blocks rarely cause symptoms on their own, though their presence may be a marker for underlying structural heart disease. 2 The key is distinguishing benign from pathological patterns:

• Always evaluate for structural heart disease with transthoracic echocardiography in newly detected cases, particularly when associated with other conduction abnormalities 2, 6
• Assess for symptoms including syncope, presyncope, dizziness, fatigue, or exercise intolerance 6
• Consider progression risk: Bifascicular block (RBBB with left anterior or posterior hemiblock) carries increased risk of progression to complete AV block 2, 1