What is the initial approach to managing right bundle branch block?

Management of Right Bundle Branch Block (RBBB)

The initial approach to managing right bundle branch block (RBBB) depends on whether it is isolated or associated with other conduction abnormalities, with asymptomatic isolated RBBB generally requiring no specific intervention beyond regular monitoring.

Definition and Diagnosis

• RBBB is characterized by QRS duration ≥120 ms in adults, an rSR' pattern in leads V1-V2, and S waves of greater duration than R waves in leads I and V6 1
• RBBB is detected in approximately 1-2.5% of the general population and may be an isolated finding or associated with underlying cardiovascular disorders 1, 2

Initial Evaluation

• Evaluate for symptoms such as syncope, presyncope, dizziness, fatigue, or exercise intolerance, which may indicate more significant conduction system disease 1
• Document the presence of any bifascicular block (RBBB plus left anterior or posterior fascicular block), which carries a higher risk of progression to complete heart block 1, 2
• Transthoracic echocardiography is reasonable if structural heart disease is suspected 1
• Ambulatory electrocardiographic monitoring is useful in symptomatic patients where atrioventricular block is suspected 1

Management Algorithm Based on Clinical Presentation

Asymptomatic Patients with Isolated RBBB

• No specific treatment is required for asymptomatic patients with isolated RBBB 1
• Regular ECG monitoring is recommended to assess for changes in conduction patterns or QRS duration 1
• Permanent pacing is not indicated in asymptomatic patients with isolated RBBB and normal 1:1 atrioventricular conduction (Class III: Harm recommendation) 1
• In a follow-up study, 94% of RBBB subjects had no evidence of cardiovascular disease at initial diagnosis 3

Symptomatic Patients with RBBB

• For patients with syncope and RBBB, consider electrophysiological study to measure HV interval 4
• Permanent pacing is recommended in patients with syncope and bundle branch block who have an HV interval ≥70 ms or evidence of infranodal block on electrophysiology study (Class I recommendation) 1
• The prognostic value of the HV interval is significant - progression rate to AV block at 4 years was 4%, 2%, and 12% for patients with HV intervals of <55 ms, 55-69 ms, and ≥70 ms respectively 4

Patients with Bifascicular Block (RBBB plus Left Anterior or Posterior Fascicular Block)

• Patients with bifascicular block are at higher risk for progression to complete heart block 1, 2
• In patients with syncope and bifascicular block, an implantable loop recorder or pacemaker implantation may be considered (Class IIa, level of evidence C) 4
• In a recent study, patients with bifascicular block (BFB) showed a statistically significant association with increased all-cause mortality 2

Patients with Alternating Bundle Branch Block

• Permanent pacing is recommended in patients with alternating bundle branch block (QRS complexes with alternating LBBB and RBBB morphologies) (Class I recommendation) 1
• This presentation suggests trifascicular conduction system disease and intermittent or impending high-degree AV block 4

Special Considerations

Medication Precautions

• Flecainide is contraindicated in patients with RBBB when associated with a left hemiblock (bifascicular block), unless a pacemaker is present 5
• If second- or third-degree AV block, or right bundle branch block associated with a left hemiblock occur during flecainide therapy, the medication should be discontinued unless a temporary or implanted ventricular pacemaker is in place 5
• Be cautious with medications that may further impair cardiac conduction in patients with RBBB 6

Diagnostic Challenges

• RBBB can sometimes mask other conditions such as Brugada syndrome, which might be demonstrated by relief of RBBB or by spontaneous or drug-induced ST-segment elevation 7
• "Masquerading" RBBB (RBBB with left anterior fascicular block) can mimic left bundle branch block in standard leads, potentially leading to missed diagnosis 8

Follow-up and Prognosis

• Regular ECG monitoring is recommended to assess for changes in conduction patterns or QRS duration 1
• Watch for symptoms of worsening cardiac conduction, including dizziness, syncope, or palpitations 1
• In a general population cohort with no cardiovascular disease, patients with isolated incomplete RBBB showed no increased risk of morbidity or mortality 2
• However, patients with incomplete RBBB who progressed to complete RBBB had a higher incidence of heart failure and chronic kidney disease 2