What is the evaluation and management of Right Bundle Branch Block (RBBB)?

Evaluation of Right Bundle Branch Block (RBBB)

In patients with newly detected RBBB, perform a comprehensive history and physical examination, obtain a 12-lead ECG to confirm the diagnosis, and proceed with transthoracic echocardiography if structural heart disease is suspected, followed by ambulatory monitoring in symptomatic patients to exclude intermittent high-degree AV block. 1

Initial Clinical Assessment

History and Physical Examination

• A comprehensive history and physical examination should be performed in all patients with suspected or documented RBBB 1
• Specifically assess for:
  • Symptoms of bradycardia (lightheadedness, syncope, presyncope, fatigue) 1
  • Symptoms of heart failure (dyspnea, orthopnea, edema) 1
  • Family history of cardiomyopathy or sudden cardiac death 2
  • History of ischemic heart disease, hypertension, or valvular disease 3
  • Presence of neuromuscular diseases (Kearns-Sayre syndrome, Anderson-Fabry disease, muscular dystrophies) 1

Electrocardiographic Confirmation

12-Lead ECG Criteria for Complete RBBB

• QRS duration ≥120 ms in adults 1
• Secondary R wave (R') in lead V1 or V2, creating an rSR', rsR', or rSR' pattern 1
• S wave of greater duration than R wave or >40 ms in leads I and V6 1
• Normal R peak time in leads V5 and V6 but >50 ms in lead V1 1

Incomplete RBBB has the same QRS morphology criteria but with QRS duration between 110-119 ms 1

Risk Stratification Based on Clinical Context

Asymptomatic RBBB

• Isolated RBBB in asymptomatic patients without structural heart disease generally has a benign prognosis 3, 4
• In apparently healthy men, RBBB showed no excess ischemic heart disease incidence, no progression to advanced AV block, and no sudden death over long-term follow-up 4
• However, permanent pacing is NOT indicated in asymptomatic patients with isolated conduction disease and 1:1 atrioventricular conduction 1

Symptomatic RBBB or RBBB with Additional Risk Factors

• RBBB with syncope requires more aggressive evaluation for intermittent high-degree AV block 1
• RBBB in the setting of acute MI is associated with increased mortality risk, though it does not necessarily indicate need for urgent angiography unless accompanied by ischemic symptoms 5
• RBBB combined with fascicular blocks (bifascicular block) indicates more extensive conduction system disease with higher risk of progression to complete heart block 2, 6

Diagnostic Testing Algorithm

Transthoracic Echocardiography

• Transthoracic echocardiography is reasonable for patients with RBBB when structural heart disease is suspected 2
• Evaluate for:
  • Left and right ventricular systolic function 2, 6
  • Cardiomyopathy (dilated, hypertrophic, arrhythmogenic right ventricular cardiomyopathy) 2, 6
  • Valvular heart disease 6
  • Congenital heart disease 1

Advanced Imaging (When Echocardiography is Unrevealing)

• If structural heart disease is suspected but echocardiogram is unrevealing, advanced imaging with cardiac MRI, CT, or nuclear studies is reasonable 1, 2
• Cardiac MRI is particularly useful for detecting:
  • Infiltrative cardiomyopathies (sarcoidosis, amyloidosis) 2, 6
  • Myocarditis 1, 2
  • Arrhythmogenic right ventricular cardiomyopathy 7
  • Subclinical cardiomyopathy 1, 6

Ambulatory Electrocardiographic Monitoring

• Cardiac rhythm monitoring is useful to establish correlation between heart rate or conduction abnormalities with symptoms 1
• The specific type of cardiac monitor should be chosen based on the frequency and nature of symptoms, as well as patient preferences 1
• In selected asymptomatic patients with extensive conduction system disease (such as bifascicular block), ambulatory electrocardiographic recording may be considered to document suspected higher degree of atrioventricular block 1, 2

Stress Testing

• In selected asymptomatic patients with RBBB in whom ischemic heart disease is suspected, stress testing with imaging may be considered 1, 2
• Note that RBBB does not interfere with stress test interpretation for ischemia detection as significantly as LBBB does 2

Electrophysiological Study (EPS)

• In patients with symptoms suggestive of intermittent bradycardia (lightheadedness, syncope) with conduction system disease identified by ECG and no demonstrated atrioventricular block, EPS is reasonable 1, 8
• In patients with syncope and bundle branch block who are found to have an HV interval ≥70 ms or evidence of infranodal block at EPS, permanent pacing is recommended 1

Special Clinical Scenarios

RBBB with Alternating Bundle Branch Block

• In patients with alternating bundle branch block (alternation between RBBB and LBBB), permanent pacing is recommended due to high risk of developing complete heart block 1

RBBB in Neuromuscular Diseases

• In patients with Kearns-Sayre syndrome and conduction disorders, permanent pacing is reasonable, with additional defibrillator capability if appropriate and meaningful survival >1 year is expected 1
• In patients with Anderson-Fabry disease and QRS prolongation >110 ms, permanent pacing with additional defibrillator capability may be considered if meaningful survival >1 year is expected 1

RBBB in Acute Coronary Syndrome

• RBBB in patients with suspected MI is associated with increased mortality risk 5, 9
• However, RBBB alone does not trigger urgent angiography unless accompanied by ischemic symptoms, as the likelihood of MI is similar to patients without bundle branch block 5
• RBBB was associated with worse prognosis in patients with reduced LV systolic function following MI 9

RBBB with Bifascicular Block

• RBBB combined with left anterior or left posterior fascicular block indicates more extensive conduction system disease 2
• Ambulatory monitoring should be strongly considered even in asymptomatic patients to exclude intermittent high-degree AV block 2
• Regular clinical and ECG follow-up is recommended, with frequency determined by symptoms and underlying heart disease 2

Common Pitfalls and Caveats

Do Not Assume All RBBB is Benign

• While isolated RBBB in asymptomatic patients without structural heart disease generally has good prognosis, RBBB may be the first manifestation of progressive cardiac conduction disease or cardiomyopathy 2
• Always evaluate for underlying structural heart disease, especially in symptomatic patients 2

Do Not Miss Intermittent or Rate-Dependent RBBB

• Use appropriate duration of ambulatory monitoring to capture intermittent conduction abnormalities 2
• Rate-dependent RBBB may indicate underlying conduction system disease 1

Do Not Overlook Bifascicular Block

• RBBB combined with fascicular blocks represents more extensive conduction system disease with higher risk of progression 2
• These patients require closer monitoring even if asymptomatic 2

Consider Underlying Infiltrative Diseases

• Infiltrative cardiomyopathies (sarcoidosis, amyloidosis) can cause conduction disease before overt structural changes appear on standard echocardiography 2
• Maintain low threshold for advanced imaging if clinical suspicion exists 2, 6