Prevalence of RBBB in Healthy Adolescents
In healthy adolescents, complete right bundle branch block (RBBB) is found in approximately 1.6% of the population with no underlying cardiac pathology, while incomplete RBBB is more common and considered a normal variant in children and adolescents. 1
Complete vs. Incomplete RBBB in Adolescents
Complete RBBB
- Defined by QRS duration >100 ms in children ages 4-16 years 2
- Characterized by:
- rSR', rsR, or rSR pattern in leads V1 or V2
- S wave of greater duration than R wave or >40 ms in leads I and V6
- Normal R peak time in V5 and V6 but >50 ms in lead V1 2
- Complete RBBB was the most common major ECG abnormality (1.6%) in a large study of adolescents 1
- Associated with height irrespective of age, sex, and BMI
- More frequent in students regularly practicing physical activity (1.80% vs. 1.02%) 1
Incomplete RBBB
- Defined by QRS duration between 90-100 ms in children 4-16 years 2
- In children, may be diagnosed when terminal rightward deflection is <40 ms but ≥20 ms 2
- Higher prevalence in underweight adolescents (21.58% vs. 15.10% in non-underweight students) 1
- Considered a normal variant in children, particularly when:
- Lead V1 is recorded higher than or to the right of normal position
- r is less than 20 ms 2
- An rSR' pattern in V1 and V2 with normal QRS duration is explicitly recognized as a normal variant in children 2
Clinical Significance and Evaluation
- The 2017 International Recommendations for ECG Interpretation in Athletes classifies complete RBBB as a "borderline" ECG finding that in isolation likely does not represent pathologic cardiovascular disease 2
- However, the presence of two or more borderline findings may warrant additional investigation 2
- A 2024 study found that CRBBB-related cardiac conditions were identified in only 5% of young individuals (14-35 years) with CRBBB 3
- Pathology was more frequently identified in individuals with:
- Non-isolated CRBBB (14% vs. 1% for isolated CRBBB)
- QRS duration ≥130 ms (10% vs. 1% for QRS <130 ms) 3
Practical Implications
- High inter-reader variability exists in the identification of incomplete RBBB, with prevalence ranging from 1-20% among different readers 4
- Despite increased use of echocardiography in patients with IRBBB, it was not associated with increased rate of echocardiographic findings compared to normal ECGs 4
- In young individuals, CRBBB is more prevalent in males and athletes (0.20% vs. 0.06% in females; 0.25% vs. 0.14% in non-athletes) 3
Conclusion
The prevalence of complete RBBB in healthy adolescents is approximately 1.6%, while incomplete RBBB is more common and considered a normal variant. The presence of isolated RBBB in adolescents rarely indicates underlying cardiac pathology, especially when QRS duration is <130 ms and no other ECG abnormalities are present.