Management of Right Bundle Branch Block (RBBB)

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

The American College of Cardiology recommends evaluating 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 2, 1
The American College of Cardiology recommends a transthoracic echocardiogram to exclude structural heart disease in patients with newly detected LBBB (Class I recommendation) 2
For RBBB, transthoracic echocardiography is reasonable if structural heart disease is suspected 2
Ambulatory electrocardiographic monitoring is useful in symptomatic patients with conduction system disease where atrioventricular block is suspected (Class I recommendation) 2

In asymptomatic patients with isolated RBBB and normal 1:1 atrioventricular conduction, permanent pacing is not indicated (Class III: Harm recommendation) 3
The American College of Cardiology recommends permanent pacing 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) 3
The European Heart Journal reports that the presence of bundle branch block in a patient with syncope is a predictor for abnormal conduction properties identified at electrophysiology study 4
Permanent pacing is recommended in patients with alternating bundle branch block (QRS complexes with alternating LBBB and RBBB morphologies) (Class I recommendation) 3

Patients with bifascicular block (RBBB plus left anterior or posterior fascicular block) are at higher risk for progression to complete heart block 4, 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
Be cautious with medications that may further impair cardiac conduction in patients with RBBB 1

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 patients with bifascicular block, closer monitoring is warranted due to the higher risk of progression to complete heart block 4, 1

The American College of Cardiology describes the distinctive double-peaked appearance of the QRS complex, known as "rabbit ears", which consists of an initial small r wave, a deep S wave, and a second, taller R wave (R'), creating the rSR' configuration, most prominently visible in right precordial leads V1 and V2 5
The rSR' pattern is characterized by an initial small r wave 6

The American College of Cardiology considers incomplete RBBB in athletes as a normal finding when isolated and asymptomatic, with the same rSR' morphology but QRS duration 110-119 ms 5
The American Heart Association notes that Brugada syndrome is a pathologic condition to exclude, characterized by downward coved or saddleback ST-segment elevations in V1-V3, distinct from simple rSR' 6, 7

The European Society of Cardiology recommends assessing for bifascicular block (RBBB plus left anterior or posterior fascicular block), which carries higher risk, in asymptomatic patients with isolated rSR' pattern 8

The American Heart Association notes that in patients with repaired tetralogy of Fallot, RBBB is present in the vast majority, and an RBBB configuration during tachycardia does not reliably distinguish ventricular tachycardia from supraventricular tachycardia 9