How is Left Bundle Branch Block (LBBB) or Right Bundle Branch Block (RBBB) managed?

Management of Left Bundle Branch Block (LBBB) and Right Bundle Branch Block (RBBB)

Bundle branch blocks should be managed based on symptoms, associated cardiac conditions, and risk stratification, with permanent pacing recommended for symptomatic patients with evidence of conduction system disease, while asymptomatic isolated bundle branch blocks generally require only monitoring. 1

Initial Evaluation

• A comprehensive clinical assessment is necessary to determine if the patient with bundle branch block is symptomatic or asymptomatic 2
• A 12-lead ECG is required to confirm the diagnosis and look for additional conduction abnormalities 1, 2
• Transthoracic echocardiography is recommended to exclude structural heart disease in all patients with newly detected LBBB 3
• Advanced cardiac imaging (cardiac MRI, CT, nuclear studies) is reasonable in selected patients with LBBB when structural heart disease is suspected but not evident on echocardiography 1, 2

Risk Stratification

• LBBB is considered a high-risk feature in patients with syncope, particularly when associated with severe structural or coronary artery disease 3
• RBBB with left anterior or posterior fascicular block requires monitoring and further evaluation 2
• Syncope during exertion or in supine position is a high-risk feature in patients with bundle branch blocks 3
• Family history of sudden cardiac death is a high-risk feature in patients with conduction disorders 3

Diagnostic Workup for Symptomatic Patients

• Ambulatory ECG monitoring (24-hour to 14-day) is necessary to detect potential intermittent AV block in symptomatic patients 1, 2
• Electrophysiology study (EPS) is reasonable in patients with symptoms suggestive of intermittent bradycardia with conduction system disease identified by ECG 1, 3
• Exercise testing is reasonable if symptoms are exercise-related or to assess chronotropic competence 2

Management Approach

Asymptomatic Patients

• No specific treatment is indicated for asymptomatic patients with isolated RBBB or LBBB and 1:1 AV conduction 1, 2
• Observation with annual follow-up with ECG is recommended to monitor for progression of conduction disease in asymptomatic patients with bundle branch blocks 2
• Unnecessary permanent pacing in asymptomatic patients with isolated bundle branch block is not indicated and may cause harm (Class III: Harm) 1, 2

Symptomatic Patients

• Permanent pacing is recommended for patients with syncope and bundle branch block who have an HV interval ≥70 ms or evidence of infranodal block at EPS (Class I recommendation) 1, 3
• Permanent pacing is recommended in patients with alternating bundle branch block (LBBB alternating with RBBB), regardless of symptoms (Class I recommendation) 1, 3
• In patients with Kearns-Sayre syndrome and conduction disorders, permanent pacing is reasonable, with additional defibrillator capability if appropriate 1

Special Considerations for LBBB

• Cardiac resynchronization therapy (CRT) may be considered in patients with LBBB, heart failure, and mildly to moderately reduced LVEF (36-50%) with QRS ≥150 ms (Class IIb recommendation) 1, 3
• In patients with atrioventricular block who require permanent pacing with LVEF between 36% and 50% and are expected to require ventricular pacing >40% of the time, pacing methods that maintain physiologic ventricular activation (e.g., CRT or His bundle pacing) are reasonable over right ventricular pacing 1
• LBBB may cause electrical and mechanical ventricular dyssynchrony, affecting regional myocardial function, which can be improved by biventricular pacing in carefully selected patients 4

Special Clinical Scenarios

• In tetralogy of Fallot patients, RBBB is common after repair and requires special attention 1
• In Ebstein's anomaly, RBBB may coexist with accessory pathways, requiring careful evaluation 1
• LBBB may be the first manifestation of a more diffuse myocardial disease and warrants thorough cardiac evaluation 5
• Patients with LBBB and normal left ventricular dimensions may present with abnormal increase in pulmonary artery pressure during exercise, suggesting latent cardiomyopathy 5

Common Pitfalls to Avoid

• Misdiagnosing ventricular tachycardia as SVT with RBBB aberrancy, especially in patients with structural heart disease 2
• Unnecessary permanent pacing in asymptomatic patients with isolated bundle branch block 1, 2
• Failing to recognize that vasodepressor mechanisms may be responsible for syncope in LBBB patients, not just bradyarrhythmias 3
• Overlooking the possibility of progressive conduction system disease in patients with bundle branch blocks, especially when combined with other conduction abnormalities 1