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

Workup for Right Bundle Branch Block (RBBB)

For patients with newly detected right bundle branch block (RBBB), a focused cardiac evaluation is recommended to exclude underlying structural heart disease, with the specific workup guided by the presence of symptoms and risk factors. 1

Initial Evaluation

• 12-lead ECG: Confirm RBBB diagnosis using standard criteria 1:

  • rsr', rsR', or rSR' pattern in leads V1 or V2
  • S wave duration greater than R wave or >40 ms in leads I and V6
  • Normal R peak time in leads V5 and V6 but >50 ms in lead V1
  • QRS duration ≥120 ms

• Comprehensive history: Focus on:

  • Cardiac symptoms (syncope, presyncope, palpitations, dyspnea, chest pain)
  • Risk factors for cardiovascular disease
  • Family history of sudden cardiac death or cardiomyopathy
  • Medication use that may affect cardiac conduction

• Physical examination: Assess for signs of structural heart disease or hemodynamic compromise

Diagnostic Testing

For Asymptomatic Patients with Isolated RBBB:

1. Transthoracic echocardiography: Reasonable if structural heart disease is suspected 1

   • While echocardiography is definitively recommended for LBBB, it is considered reasonable (Class IIa) for RBBB when structural heart disease is suspected

2. No further testing required if:

   • No symptoms
   • No evidence of structural heart disease on initial evaluation
   • No other conduction abnormalities

For Symptomatic Patients or Those with Additional Conduction Abnormalities:

1. Ambulatory ECG monitoring: Recommended for patients with symptoms suggestive of intermittent bradycardia or higher-degree AV block 1

   • 24-48 hour Holter monitoring for frequent symptoms
   • Event recorder or mobile cardiac telemetry for less frequent symptoms
   • Implantable loop recorder for very infrequent symptoms

2. Exercise stress testing: Consider for:

   • Evaluation of exercise capacity and heart rate response
   • Assessment of exercise-induced conduction abnormalities
   • Patients with suspected ischemic heart disease

3. Advanced cardiac imaging: Consider in selected cases with suspected structural heart disease:

   • Cardiac MRI
   • CT angiography
   • Nuclear studies

4. Electrophysiology study (EPS): Reasonable in patients with symptoms suggestive of intermittent bradycardia with no demonstrated AV block on monitoring 1

Special Considerations

Bifascicular Block (RBBB + Left Anterior or Posterior Fascicular Block):

• Higher risk of progression to complete heart block
• Consider ambulatory ECG monitoring to detect higher-degree AV block 1
• More aggressive evaluation may be warranted

Athletes with RBBB:

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

RBBB in Acute Settings:

• In patients with suspected acute myocardial infarction, new or presumably new RBBB should prompt consideration for reperfusion therapy 1
• RBBB with a QR pattern in V1 has high positive predictive value for high-risk pulmonary embolism 2

Clinical Implications

Recent evidence suggests that even isolated RBBB without known cardiovascular disease may be associated with increased risk of all-cause mortality and cardiovascular-related mortality 3. This challenges the traditional view of RBBB as a completely benign finding and may warrant closer follow-up in some patients.

Follow-up Recommendations

• Asymptomatic patients with isolated RBBB and no evidence of structural heart disease: routine follow-up
• Patients with bifascicular block: consider periodic ambulatory monitoring to detect progression
• Any development of symptoms (syncope, presyncope) should prompt immediate reevaluation

Remember that while RBBB is often benign, it can be a marker of underlying cardiac disease in some patients, and the workup should be tailored to identify potential cardiovascular pathology that could affect morbidity and mortality.