What is the workup for a right bundle branch block (RBBB)?

Workup for Right Bundle Branch Block (RBBB)

A patient with right bundle branch block (RBBB) requires a cardiac evaluation including history, physical examination, ECG, echocardiogram, and exercise stress test to rule out underlying structural heart disease or conduction system abnormalities. 1

Initial Assessment

• History: Focus on:

  • Symptoms (syncope, presyncope, dizziness, palpitations)
  • Exercise-related symptoms
  • Family history of sudden cardiac death or cardiomyopathy
  • Risk factors for cardiovascular disease

• Physical examination: Assess for:

  • Signs of heart failure
  • Murmurs suggesting structural heart disease
  • Blood pressure abnormalities

• 12-lead ECG: Confirm RBBB diagnosis using established criteria:

  • QRS duration ≥120 ms in adults
  • rSR' pattern in leads V1-V2
  • Wide S waves in leads I and V6 2

Risk Stratification

Higher Risk Features (Require More Extensive Workup)

• Syncope or presyncope
• Exercise-related symptoms
• Family history of sudden cardiac death
• Coexisting left anterior fascicular block (bifascicular block)
• Prolonged PR interval
• Structural heart disease

Basic Diagnostic Workup

1. Echocardiogram: Essential for all patients with RBBB to:

   • Evaluate for structural heart disease
   • Assess ventricular size and function
   • Rule out congenital heart disease 1

2. Exercise stress test: Recommended to:

   • Assess for exercise-induced symptoms
   • Evaluate for ischemic heart disease
   • Determine functional capacity 1

Advanced Testing (Based on Risk and Initial Findings)

1. 24-hour ambulatory ECG monitoring:

   • Indicated for patients with symptoms suggesting arrhythmias
   • Essential for those with syncope, presyncope, or palpitations
   • Helps detect progression to higher-degree AV block 1

2. Electrophysiologic study (EPS):

   • Reserved for selected high-risk patients:
     • Those with syncope and RBBB
     • RBBB with left anterior fascicular block (bifascicular block)
     • When progression to higher-degree AV block is suspected 1

3. Cardiac MRI:

   • Consider in patients with suspected:
     • Arrhythmogenic right ventricular cardiomyopathy (ARVC)
     • Sarcoidosis
     • Other infiltrative cardiomyopathies 2

Special Considerations

Bifascicular Block (RBBB + Left Anterior Fascicular Block)

• Higher risk of progression to complete heart block
• More intensive evaluation warranted, including:
  • Electrophysiologic study in symptomatic patients
  • More frequent monitoring 2

Asymptomatic RBBB Without Structural Heart Disease

• Generally has favorable prognosis
• Annual progression to complete AV block is approximately 1-2% 2
• Recent evidence suggests increased long-term cardiovascular mortality even in those without known cardiovascular disease 3

RBBB in Athletes

• Athletes with RBBB who do not develop type II second-degree AV block or complete heart block during exercise and have no symptoms or structural heart disease can participate in all competitive athletics 1

Pitfalls and Caveats

1. Don't assume RBBB is always benign:

   • Recent studies show increased all-cause and cardiovascular mortality even in patients without known cardiovascular disease 3

2. Don't miss bifascicular block:

   • RBBB with left anterior fascicular block carries higher risk for progression to complete heart block 1, 2

3. Beware of rate-dependent conduction abnormalities:

   • Consider pharmacological stress testing rather than exercise stress in some patients 2

4. Don't overlook ARVC:

   • RBBB may be a manifestation of ARVC, particularly when associated with epsilon waves or delayed S-wave upstroke in V1-V3 1

The workup for RBBB should be thorough but proportionate to the patient's risk factors, with more extensive evaluation for those with symptoms, bifascicular block, or evidence of structural heart disease.