What is the appropriate workup and treatment for a patient presenting with a right bundle branch block (RBBB)?

Workup for Right Bundle Branch Block

In patients with newly detected right bundle branch block (RBBB), obtain transthoracic echocardiography if structural heart disease is suspected, along with ambulatory ECG monitoring in symptomatic patients to evaluate for intermittent high-grade AV block. 1

Initial Clinical Assessment

Symptom Evaluation

• Assess specifically for syncope, presyncope, dizziness, fatigue, or exercise intolerance, as these symptoms suggest potential progression to higher-degree AV block or underlying structural disease 2, 3
• Document any palpitations or near-syncope episodes that may indicate intermittent higher-degree AV block 3
• Evaluate for family history of sudden cardiac death, which warrants genetic evaluation 2

ECG Analysis

• Confirm complete RBBB with QRS duration ≥120 ms, rSR' pattern in V1-V2, and S waves of greater duration than R waves in leads I and V6 4
• Identify any additional conduction abnormalities including left anterior or posterior hemiblock (bifascicular block) or first-degree AV block, as these combinations carry higher risk for progression to complete heart block 3
• Look for epsilon waves or localized QRS prolongation in V1-V3, which may suggest arrhythmogenic right ventricular cardiomyopathy (ARVC) 1, 2
• Exclude Brugada pattern (ST-elevation in V1-V3 with RBBB morphology), which requires immediate specialized evaluation due to sudden cardiac death risk 2

Diagnostic Testing Algorithm

Cardiac Imaging

Transthoracic echocardiography is reasonable in selected patients with RBBB if structural heart disease is suspected 1. This is a Class IIa recommendation, though the threshold is lower than for left bundle branch block since isolated RBBB is less commonly associated with structural disease 3.

• Assess for right ventricular enlargement, dysfunction, or other structural abnormalities 2, 3
• Evaluate for conditions such as ischemic heart disease, hypertensive heart disease, cardiomyopathies, or congenital heart disease 1, 2
• Consider cardiac MRI in selected patients when sarcoidosis, myocarditis, or infiltrative cardiomyopathies are suspected clinically, even with normal echocardiography, as cardiac MRI detects subclinical abnormalities in 33-42% of patients with conduction disease and normal echocardiograms 3

Ambulatory ECG Monitoring

In symptomatic patients with RBBB in whom AV block is suspected, ambulatory electrocardiographic monitoring is useful (Class I recommendation) 1

• Obtain 24-hour to 14-day ambulatory ECG monitoring to establish symptom-rhythm correlation and detect intermittent higher-degree AV block 3
• In selected asymptomatic patients with extensive conduction system disease (bifascicular block), ambulatory monitoring may be considered to document suspected higher degree of AV block 1

Exercise Testing

Cardiological work-up including exercise testing is recommended in athletes with complete bundle branch block 1

• Exercise testing helps evaluate for underlying pathological causes 1, 4
• Patients with RBBB demonstrate decreased functional aerobic capacity, slower heart rate recovery, and more dyspnea on exercise testing compared to those without RBBB 5

Electrophysiology Study

In patients with symptoms suggestive of intermittent bradycardia (e.g., lightheadedness, syncope), with RBBB identified by ECG and no demonstrated AV block, an EPS is reasonable (Class IIa recommendation) 1

• Proceed to electrophysiology study to measure HV interval in patients with syncope where other testing is unrevealing 3
• Permanent pacing is definitively indicated when syncope occurs with RBBB and EPS demonstrates HV interval ≥70 ms (Class I, Level C-LD) 3

Laboratory Testing

Laboratory tests based on clinical suspicion for potential underlying causes are reasonable (Class IIa recommendation) 1

• Consider thyroid function tests, Lyme titer, potassium, and pH based on clinical context 1

Special Populations and Contexts

Athletes

• Complete RBBB occurs in <2% of athletes and represents a potential marker of serious underlying cardiovascular disease 1
• Demonstration of complete bundle branch block should lead to cardiological work-up including exercise testing, 24-hour ECG, and imaging 1
• ECG screening of siblings is recommended if bifascicular block is present in a young athlete 3

Acute Myocardial Infarction

• In acute MI with new RBBB and first-degree AV block, transcutaneous pacing capability should be available (Class I recommendation) 3
• Temporary transvenous pacing may be considered (Class IIb) 3

Asymptomatic Patients with Isolated RBBB

In asymptomatic patients with isolated RBBB and no clinical evidence of structural heart disease, routine cardiac imaging is not indicated (Class III: No Benefit) 1

• However, regular follow-up with ECG monitoring is recommended to detect progression to more complex conduction disorders 3
• RBBB may be a marker of early cardiovascular disease even in asymptomatic patients, as studies show increased all-cause mortality (HR 1.5) and cardiovascular-related mortality (HR 1.7) over long-term follow-up 5

Common Pitfalls to Avoid

• Do not dismiss RBBB as entirely benign: While isolated RBBB may represent idiopathic conduction delay, it can be associated with serious underlying conditions including ischemic heart disease, cardiomyopathies, myocarditis, sarcoidosis, and ARVC 1, 2
• 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
• Consider ARVC in the differential: Look for epsilon waves, T-wave inversions in V1-V3, and family history of sudden death 1, 2
• Distinguish from acute pulmonary embolism: Newly emerged RBBB in the setting of acute dyspnea may indicate massive pulmonary trunk obstruction 6