What is a right bundle branch block (RBBB) and what is its clinical significance?

What is Right Bundle Branch Block (RBBB)?

Right bundle branch block (RBBB) is a conduction delay through the right bundle branch causing delayed right ventricular activation, characterized on ECG by QRS duration ≥120 ms, an rSR' pattern in V1-V2, and wide S waves in leads I and V6. 1, 2

Definition and ECG Characteristics

RBBB represents an interruption of electrical conduction through the right bundle branch of the cardiac conduction system, resulting in delayed activation of the right ventricle. 1, 3

Key diagnostic ECG criteria include:

• QRS duration ≥120 ms in adults (>100 ms in children 4-16 years, >90 ms in children <4 years) 2
• Classic rSR', rsR', or rSR pattern in leads V1-V2, with the R' deflection typically wider than the initial R wave 2
• S wave duration greater than R wave or >40 ms in leads I and V6 2
• Normal R peak time in V5-V6 but >50 ms in V1 2
• Some cases show a wide, notched R wave in V1-V2 instead of the typical rSR' pattern 2

Clinical Significance and Prevalence

RBBB can range from a benign incidental finding to a marker of serious underlying cardiovascular disease, requiring careful clinical evaluation to distinguish between these scenarios. 1

Prevalence

• Detected in approximately 1% of the general population 2
• Occurs in 0.6% of males and 0.3% of females under age 40 1
• Found in less than 2% of athletes 1, 2

When RBBB May Be Benign

Complete RBBB in healthy individuals/athletes may represent an idiopathic, isolated, and clinically benign conduction interruption through the right bundle branch. 1 However, this determination requires excluding pathological causes through appropriate workup. 1

When RBBB Signals Serious Disease

Bundle branch block may develop from primary degenerative lesions of specialized conducting tissue or from a variety of serious cardiac pathologies. 1 The pathophysiology can be developmental, hereditary/genetic, metabolic, infectious, inflammatory, infiltrative, traumatic, ischemic, malignant, or degenerative. 3

Specific concerning etiologies include:

• Ischemic heart disease: Particularly anterior infarction with persistent intraventricular conduction disturbances carries an unfavorable prognosis 3
• Cardiomyopathies: Including arrhythmogenic right ventricular cardiomyopathy (ARVC), which shows localized QRS prolongation in V1-V3 with epsilon waves 1, 3
• Myocarditis and infectious diseases: Including Chagas' disease 1, 3
• Infiltrative processes: Sarcoidosis, cardiac tumors 1, 3
• Congenital heart disease: Both unoperated and operated, including atrial septal defects and Ebstein's anomaly 1, 3
• Channelopathies: Including Lenegre disease (progressive cardiac conduction disease), an autosomal dominant SCN5A gene mutation causing various conduction defects in young individuals 1, 3
• Hypertensive heart disease 3

Critical Clinical Pitfalls and Red Flags

Always evaluate for structural heart disease with transthoracic echocardiography in newly detected RBBB, particularly when associated with other conduction abnormalities. 3

Immediate Specialized Evaluation Required For:

• RBBB pattern with ST-elevation in V1-V3 (Brugada pattern) due to sudden cardiac death risk 3
• Syncope, palpitations at time of syncope, or exertional symptoms suggesting arrhythmic etiology 3
• Family history of sudden cardiac death warranting genetic evaluation 3
• Symptoms suggesting ARVC (family history of sudden death, ventricular arrhythmias) 3

High-Risk Combinations:

Bifascicular block (RBBB with left anterior or posterior hemiblock) carries increased risk of progression to complete AV block. 1, 3 Combinations of bundle branch block and hemiblock reflect more extensive involvement of the specialized conduction system. 1

Specific Symptoms to Assess:

• Syncope or presyncope 3
• Dizziness 3
• Fatigue 3
• Exercise intolerance 3
• Palpitations 3

Recommended Workup

The European Society of Cardiology recommends that demonstration of complete bundle branch block should lead to a cardiological work-up including exercise testing, 24-hour ECG monitoring, and imaging to evaluate for underlying pathological causes. 1, 2

Specific evaluation components:

• Transthoracic echocardiography to rule out structural heart disease (Ebstein anomaly, hypertrophic cardiomyopathy, glycogen storage cardiomyopathy) 2, 3
• Exercise stress testing 1, 2
• 24-hour Holter monitoring 1, 2
• Family screening: ECG should be obtained in siblings of young patients with bifascicular block to exclude genetically determined progressive cardiac conduction disease 1

Functional Consequences

In heart failure patients, RBBB is an important predictor of mortality comparable to left bundle branch block. 4 Research shows that 50% of patients with RBBB have left ventricular mechanical dyssynchrony, with an odds ratio of 3.6 compared to those without RBBB. 5

In athletes with complete RBBB, studies demonstrate larger right ventricular dimensions and lower right ventricular ejection fraction but preserved fractional area change compared to those with normal QRS complexes. 2

Procedural Considerations

In patients undergoing transcatheter aortic valve replacement (TAVR), pre-existing RBBB significantly increases the need for permanent pacemaker implantation (adjusted OR: 4.18), cardiac arrest (adjusted OR: 2.46), and post-procedural heart failure (adjusted OR: 2.75). 6