What is the recommended work‑up and management for a patient found to have a right bundle branch block on electrocardiogram?

Right Bundle Branch Block Work-Up

Initial Assessment

In a patient with newly discovered RBBB, the work-up should be guided primarily by symptom status, with asymptomatic isolated RBBB requiring minimal evaluation while symptomatic patients need urgent investigation for high-grade conduction disease. 1, 2

Symptom Evaluation

• Specifically inquire about syncope, presyncope, lightheadedness, or dizziness – these symptoms dramatically change management and suggest potential progression to higher-degree AV block, warranting urgent electrophysiology referral 1, 2
• Document palpitations or near-syncope episodes that may indicate intermittent higher-degree AV block 2
• Assess for exertional symptoms including fatigue, dyspnea, or exercise intolerance 2
• Evaluate family history of sudden cardiac death, which warrants genetic evaluation 2

ECG Analysis Beyond RBBB

• Examine for bifascicular block (RBBB plus left anterior or posterior hemiblock) – this combination carries increased risk of progression to complete AV block and requires more intensive evaluation 1, 2, 3
• Check for first-degree AV block in addition to RBBB, which represents more extensive conduction system disease 1
• Look for alternating bundle branch block (QRS complexes alternating between RBBB and LBBB morphologies) – this is a Class I indication for permanent pacing due to high likelihood of sudden complete heart block 1
• Review prior ECGs to determine if RBBB is new or chronic 2

Diagnostic Testing Algorithm

For Asymptomatic Isolated RBBB

• No specific testing is required – observation only is recommended, as permanent pacing is contraindicated (Class III: Harm) in asymptomatic patients with isolated conduction disease and 1:1 AV conduction 1
• Transthoracic echocardiography is reasonable (Class IIa) if structural heart disease is suspected based on clinical examination, though RBBB has lower association with structural disease compared to LBBB 1, 2

For Symptomatic RBBB

• Ambulatory ECG monitoring (Class I recommendation) – obtain 24-hour to 14-day monitoring in symptomatic patients to establish symptom-rhythm correlation and detect intermittent higher-degree AV block 1, 2
• Transthoracic echocardiography (Class IIa recommendation) – assess for right ventricular enlargement, dysfunction, ischemic heart disease, hypertensive heart disease, cardiomyopathies, or congenital heart disease 1, 2
• Electrophysiology study (Class IIa recommendation) – reasonable in patients with symptoms suggestive of intermittent bradycardia (lightheadedness, syncope) when conduction system disease is identified by ECG but no documented AV block 1

Advanced Imaging Considerations

• Cardiac MRI may be considered in selected patients when sarcoidosis, myocarditis, or infiltrative cardiomyopathies are suspected clinically, even with normal echocardiography 1, 2
• Stress testing with imaging may be considered if ischemic heart disease is suspected in selected asymptomatic patients 1

Special Clinical Contexts

Acute Myocardial Infarction

• New RBBB with prolonged ischemic chest pain indicates potential STEMI and warrants immediate cardiac catheterization for reperfusion therapy 4
• New RBBB with first-degree AV block during acute MI requires transcutaneous pacing capability (Class I) and consideration of temporary transvenous pacing (Class IIb) 1

Athletes

• Complete RBBB in athletes (<2% prevalence) represents a potential marker of serious cardiovascular disease and should lead to cardiological work-up including exercise testing, 24-hour ECG, and imaging 2, 3
• ECG screening of siblings is recommended if bifascicular block is present in a young athlete 2

Acute Pulmonary Embolism

• New RBBB on dynamic ECG monitoring is a significant sign of probable massive obstruction of the main pulmonary trunk (detected in 80% of trunk embolism cases) 5

Indications for Permanent Pacing

Class I Recommendations (Strong)

• Syncope with bundle branch block AND HV interval ≥70 ms or evidence of infranodal block at EPS 1
• Alternating bundle branch block (alternating RBBB with LBBB morphologies) due to high likelihood of sudden complete heart block 1

Class IIa Recommendations (Reasonable)

• Kearns-Sayre syndrome with conduction disorders – permanent pacing with additional defibrillator capability if appropriate and meaningful survival >1 year expected 1

Class IIb Recommendations (May Be Considered)

• Anderson-Fabry disease with QRS prolongation >110 ms – permanent pacing with defibrillator capability if needed and meaningful survival >1 year expected 1

Critical Pitfalls to Avoid

• Do not dismiss RBBB as entirely benign – it can be associated with ischemic heart disease, cardiomyopathies, myocarditis, sarcoidosis, and arrhythmogenic right ventricular cardiomyopathy 2, 3
• Always evaluate for bifascicular block – the combination of RBBB with left anterior or posterior hemiblock carries increased risk of progression to complete AV block 1, 2
• Do not implant permanent pacemakers for isolated asymptomatic RBBB – this is explicitly contraindicated (Class III: Harm) due to lack of benefit and exposure to procedural risks 1, 6
• Consider arrhythmogenic right ventricular cardiomyopathy in the differential, looking for epsilon waves, T-wave inversions in V1-V3, and family history of sudden death 2
• Distinguish incomplete RBBB from pathological patterns including type-2 Brugada ECG pattern, right ventricular enlargement, and Wolff-Parkinson-White syndrome 7
• Listen for splitting of the second heart sound as RBBB is a common finding in ostium secundum atrial septal defect 7