What is the appropriate management for a new right bundle branch block (RBBB)?

Management of New Right Bundle Branch Block (RBBB)

For a newly detected RBBB, no specific treatment is required unless there are associated symptoms or structural heart disease is suspected, in which case further evaluation is warranted.

Initial Evaluation

Asymptomatic Patients

• RBBB alone is generally considered benign and does not require specific treatment 1
• Unlike LBBB, isolated RBBB has not been strongly associated with development of coronary disease and heart failure 1
• No permanent pacemaker implantation is indicated for fascicular block without AV block or symptoms 1

Symptomatic Patients

If the patient has symptoms potentially related to bradycardia (lightheadedness, syncope):

• Ambulatory electrocardiographic monitoring is recommended to document suspected higher degree of atrioventricular block 1
• Electrophysiological study (EPS) is reasonable if symptoms suggest intermittent bradycardia with no demonstrated AV block 1

Diagnostic Workup

Echocardiography

• For RBBB, echocardiography is reasonable if structural heart disease is suspected 1
• Pay particular attention to:
  • Right ventricular size and function
  • Presence of atrial septal defect (listen for splitting of S2, as RBBB is common in ostium secundum ASD) 2
  • Evidence of pulmonary hypertension

Advanced Testing (if indicated)

• If symptoms suggest intermittent bradycardia and conduction system disease is identified, an electrophysiological study is reasonable 1
• Consider stress testing if ischemic heart disease is suspected

Special Considerations

Bifascicular Block

• If RBBB is accompanied by left anterior or posterior fascicular block (bifascicular block):
  • More vigilant monitoring is warranted
  • Consider ambulatory ECG monitoring to detect higher-degree AV block 1
  • Note that progression from bifascicular block to third-degree AV block is typically slow 1

Post-TAVR Evaluation

• New RBBB after transcatheter aortic valve replacement requires careful surveillance for bradycardia 1
• New RBBB after TAVR is associated with increased risk of PPM implantation and increased late all-cause mortality 1

Acute Myocardial Infarction Context

• New RBBB in the setting of suspected acute myocardial infarction should prompt consideration for reperfusion therapy if presenting within 12 hours of symptom onset 1

Indications for Permanent Pacing

Permanent pacemaker implantation is NOT indicated for:

• Isolated RBBB without AV block or symptoms 1
• RBBB with first-degree AV block without symptoms 1

Permanent pacemaker implantation IS indicated for:

• Alternating bundle branch block (RBBB alternating with LBBB) 1
• RBBB with syncope when other causes have been excluded 1
• RBBB with markedly prolonged HV interval (≥100 ms) found incidentally during EPS 1

Prognosis

• Isolated RBBB without structural heart disease has a generally favorable prognosis 3, 4
• Long-term prognosis is more related to any underlying cardiac condition than to the RBBB itself
• In one follow-up study, only 4% of patients with RBBB died during the follow-up period, and progression to complete heart block was rare 3

Common Pitfalls

• Don't confuse incomplete RBBB (QRS <120 ms) with complete RBBB; incomplete RBBB is often a normal variant, especially in young adults and athletes 2
• Don't miss underlying structural heart disease that may be masked by focusing only on the conduction abnormality
• Avoid unnecessary pacemaker implantation for isolated RBBB without symptoms or higher-degree AV block
• Remember that RBBB pattern may be seen in other conditions requiring different management (Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy, etc.) 2