ECG Features of Right Bundle Branch Block (RBBB)

Diagnostic Criteria

The American College of Cardiology recommends that Right bundle branch block (RBBB) be characterized by specific ECG findings including 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
The American College of Cardiology states that QRS duration ≥120 ms in adults (>100 ms in children 4-16 years, >90 ms in children <4 years) is a diagnostic criterion for complete RBBB 1
The American College of Cardiology recommends that an rSR', rsR', or rSR pattern in leads V1 or V2, with the R' deflection usually wider than the initial R wave, be used to diagnose complete RBBB 1
The American College of Cardiology states that an S wave of greater duration than R wave or >40 ms in leads I and V6 in adults is a diagnostic criterion for complete RBBB 1
The American College of Cardiology recommends that a normal R peak time in leads V5 and V6 but >50 ms in lead V1 be used to diagnose complete RBBB 1

The American College of Cardiology describes the classic RBBB pattern as showing an rSR' configuration in right precordial leads (V1-V2) 2, 3
The American College of Cardiology states that in some cases, a wide and often notched R wave pattern may be seen in leads V1 and/or V2 instead of the typical rSR' pattern 1
The American College of Cardiology recommends that RBBB reduces the amplitude of the S wave in the right precordial leads 2, 3

The American College of Cardiology states that complete RBBB must be differentiated from incomplete RBBB, which has a QRS duration between 110-120 ms in adults 1

The American College of Cardiology reports that complete RBBB is less common with a prevalence of 0.5% to 2.5% in young adult athletes 4, 5
The American College of Cardiology states that complete RBBB is detected in approximately 1% of the general population 4, 5
The American College of Cardiology recommends that in athletes with complete RBBB, studies have shown larger right ventricular dimensions and lower right ventricular ejection fraction but preserved fractional area change compared to those with normal QRS complexes 4, 5

The European Society of Cardiology recommends that demonstration of complete bundle branch block should lead to a cardiological work-up including exercise testing, 24-hour ECG monitoring, and imaging to evaluate for underlying pathological causes 6
The American College of Cardiology states that the ancillary features of left atrial abnormality and left axis deviation have enhanced value for the diagnosis of left ventricular hypertrophy in the presence of RBBB 2, 3
The American College of Cardiology recommends that special criteria for LVH in the presence of RBBB include S V1 >2 mm (0.2 mV), R V5,6 >15 mm (1.5 mV), and QRS axis to the left of -30° 2, 3

The European Society of Cardiology states that RBBB may be associated with underlying cardiovascular disorders, though it can also be an isolated and clinically benign finding 6
The American Heart Association reports that in patients with tetralogy of Fallot, RBBB is present in the vast majority of patients after repair, and SVTs are conducted with RBBB aberrancy 7
The American Heart Association states that in Ebstein's anomaly, RBBB is usually present and may be masked by ventricular pre-excitation in the presence of a right-sided accessory pathway 7

Complete right bundle branch block (RBBB) is present in approximately 1 % of the general population, with a prevalence of 0.5–2.5 % among young adult athletes and ≈0.6 % in males younger than 40 years; it may represent an isolated benign conduction delay or indicate serious underlying cardiovascular disease. 8

RBBB can be a manifestation of ischemic heart disease (especially anterior myocardial infarction with persistent conduction disturbance). 8
RBBB may arise secondary to cardiomyopathies such as dilated, hypertrophic, or arrhythmogenic right ventricular cardiomyopathy. 8
Congenital heart disease (both unoperated and post‑surgical lesions, e.g., atrial septal defects, Ebstein’s anomaly) is an established cause of RBBB. 8
Genetic conduction disorders (e.g., Lenègre disease caused by SCN5A mutations) can produce progressive RBBB in younger individuals. 8

The combination of RBBB with a left posterior fascicular block produces a right‑axis deviation greater than +90°; this pattern is uncommon but clinically relevant. 8
Bifascicular block (RBBB + left anterior or posterior hemiblock) signals extensive conduction system disease and is associated with an increased risk of progression to complete atrioventricular block, warranting closer monitoring. 8

Transthoracic echocardiography should be performed in all patients with newly identified complete RBBB to exclude structural heart disease (e.g., cardiomyopathy, ischemic disease, hypertensive heart disease, congenital anomalies). 8
A detailed family history focusing on sudden cardiac death and inherited cardiac or conduction disorders is recommended. 8

Exercise stress testing is advised when ischemia or exercise‑induced arrhythmias are suspected. 8
24‑hour Holter monitoring can identify intermittent conduction abnormalities or arrhythmias. 8

Syncope or presyncope accompanied by palpitations in a patient with RBBB mandates prompt cardiology evaluation. 8
A family history of sudden cardiac death in the setting of RBBB calls for urgent genetic and clinical assessment. 8
Presence of a bifascicular block (RBBB + left anterior or posterior hemiblock) indicates heightened risk for progression to complete AV block and should trigger expedited referral. 8
Clinical features suggestive of arrhythmogenic right ventricular cardiomyopathy (e.g., ventricular arrhythmias, localized QRS prolongation >110 ms in right precordial leads, epsilon waves) together with RBBB require immediate specialist input. 8

In asymptomatic young athletes, an isolated RBBB is often idiopathic and benign, but periodic follow‑up is advisable to monitor for any emerging structural abnormalities. 8

Do not assume RBBB is benign without imaging; echocardiographic assessment is essential even in the absence of symptoms. 8
Intermittent or rate‑dependent RBBB carries the same prognostic weight as a stable RBBB and should be managed accordingly. 8