How is a right bundle branch block (RBBB) managed?

Management of Right Bundle Branch Block (RBBB)

Asymptomatic patients with isolated RBBB and 1:1 atrioventricular conduction require observation only—permanent pacing is not indicated and may cause harm. 1, 2

Initial Assessment Algorithm

The management of RBBB depends critically on three factors: presence of symptoms (particularly syncope), associated conduction abnormalities, and underlying cardiac disease. 1

Key Clinical Features to Evaluate:

• Syncope: Presence of syncope with bundle branch block predicts abnormal conduction properties and warrants electrophysiologic study (EPS). 1
• Alternating bundle branch block: QRS complexes alternating between LBBB and RBBB morphologies indicate unstable conduction in both bundles. 1
• HV interval on EPS: An HV interval ≥70 ms or frank infranodal block indicates high-grade conduction disease. 1
• Associated fascicular blocks: Bifascicular block (RBBB with left anterior or posterior hemiblock) requires evaluation for progressive disease. 2
• Underlying neuromuscular disease: Kearns-Sayre syndrome, Anderson-Fabry disease, or Emery-Dreifuss muscular dystrophy. 1

Treatment Recommendations by Clinical Scenario

Isolated Asymptomatic RBBB

• No treatment required—observation only with regular follow-up. 1, 2
• This represents a Class III (Harm) recommendation for permanent pacing per ACC/AHA/HRS guidelines. 1
• Despite being generally benign, recent data shows RBBB may be associated with increased all-cause mortality (HR 1.5) and cardiovascular mortality (HR 1.7) even without known cardiovascular disease, suggesting it may be an early marker of subclinical disease. 3

RBBB with Syncope

• Permanent pacing is indicated (Class I) if EPS demonstrates HV interval ≥70 ms or frank infranodal block. 1
• Important caveat: Syncope in bundle branch block patients may be vasodepressor-mediated rather than heart block-mediated, so EPS helps differentiate the mechanism. 1

Alternating Bundle Branch Block

• Permanent pacing is recommended (Class I) due to high risk of sudden complete heart block with slow or absent ventricular escape. 1
• This pattern implies unstable conduction disease in both bundle branches. 1

RBBB with Specific Underlying Diseases

Kearns-Sayre syndrome with conduction disorders:

• Permanent pacing is reasonable (Class IIa), with additional defibrillator capability if appropriate and meaningful survival >1 year expected. 1
• This mitochondrial disorder has 66% incidence of conduction delays and high risk of sudden cardiac death. 1

Anderson-Fabry disease with QRS >110 ms:

• Permanent pacing may be considered (Class IIb), with defibrillator capability if needed and meaningful survival >1 year expected. 1
• QRS duration >110 ms is an independent predictor for requiring pacing therapy (HR 1.05). 1

RBBB in Acute Myocardial Infarction

• New RBBB with first-degree AV block: Transcutaneous pacing is Class I recommendation; temporary transvenous pacing is Class IIb. 2
• This represents a higher-risk scenario requiring immediate preparedness for complete heart block. 2

RBBB with Symptoms Suggesting Intermittent AV Block

• Proceed to AV block diagnostic algorithm rather than simple observation. 1
• These patients require more intensive monitoring and evaluation. 1

Critical Pitfalls to Avoid

Do not pace isolated asymptomatic RBBB: This is explicitly contraindicated (Class III: Harm) and provides no benefit while exposing patients to procedural risks and device complications. 1, 2

Do not assume all RBBB is benign: Evaluate for underlying structural heart disease, especially when new-onset, as it may represent early cardiovascular disease. 2, 3

Beware of "masquerading" RBBB: When RBBB occurs with high-degree left anterior fascicular block and severe left ventricular disease, the typical terminal forces may be concealed, mimicking LBBB and potentially missing the diagnosis. 4 This variant carries poor prognosis as it implies severe underlying heart disease. 4

In acute coronary syndrome: RBBB patients present with higher-risk features, receive fewer interventions, and have worse outcomes (8.8% vs 3.8% in-hospital mortality). 5 After adjusting for GRACE risk score components, RBBB remains an independent predictor of in-hospital death (OR 1.45). 5

Consider pulmonary embolism: RBBB with QR pattern in V1 has high positive predictive value for high-risk PE causing cardiac arrest and may warrant thrombolysis before imaging confirmation in the appropriate clinical context. 6

Follow-Up Strategy

Regular monitoring is recommended to detect development of symptoms or progression to more complex conduction disorders, though specific intervals are not defined in guidelines. 2 Patients with RBBB demonstrate decreased functional aerobic capacity, slower heart rate recovery, and more dyspnea on exercise testing compared to those without RBBB. 3