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Abstract
Background There is limited information on the clinical significance of complete right bundle branch block (CRBBB) in young asymptomatic individuals. We sought to determine the prevalence and prognostic significance of CRBBB by reporting on clinical outcomes of a nationwide cardiac screening programme for young individuals in the United Kingdom.
Methods Between 2007 and 2018, 104,369 consecutive individuals, aged 14 to 35 years, underwent voluntary cardiac screening (mean age 20.2 ± 6.2 years, 62% male, 89% white, 91% non-athletes). Initial evaluation consisted of a health questionnaire (HQ), electrocardiogram (ECG) and clinical consultation. Selective on-site transthoracic echocardiography (TTE) was available at the discretion of the consulting physician. Secondary cardiac evaluation was recommended for individuals with abnormal findings. CRBBB was classified as ‘isolated’ or ‘non-isolated’ based on the absence or presence, respectively, of concomitant cardiovascular symptoms, relevant family history and other ECG abnormalities (Table 1). Follow-up data were obtained via telephone consultations.
Results One hundred and fifty-four (0.1%) individuals were identified with CRBBB (Figure 1). The mean QRS duration was 131 ± 12 ms. CRBBB was more prevalent in males compared to females (0.22% vs. 0.06%, p < 0.05) and in athletes compared to non-athletes (0.26% vs. 0.14%, p < 0.05). There was no significant difference in terms of age or ethnicity. The majority (n=110; 74%) of individuals presented with isolated CRBBB. Of the 39 (26%) individuals with non-isolated CRBBB, 3 (2%) had CRBBB with associated symptoms and 36 (24%) had CRBBB and additional ECG finding (Table 2).
On-site TTE and or follow-up was available for 149 (97%) individuals. On-site TTE identified 4 individuals with atrial septal defects (ASD). During a mean follow-up period of 7.3 ± 2.7 years, a further 3 individuals were identified with CRBBB-related conditions, including 1 with Brugada syndrome, 1 with progressive cardiac conduction disease (PCCD) and 1 with atrial fibrillation (AF).
A total of 7 (4%) individuals were identified with CRBBB-related conditions; including 4 (3%) with ASD, 1 (0.7%) with Brugada syndrome, 1 (0.7%) with PCCD and 1 (0.7%) with AF. An additional 2 (1%) individuals were identified with non-CRBBB-related cardiac conditions which could be considered incidental findings; including 1 (0.7%) with mitral valve prolapse, and 1 (0.7%) aortic coarctation.
The prevalence of CRBBB-related cardiac conditions was significantly greater in individuals with non-isolated CRBBB compared to individuals with isolated CRBBB (15% vs 3%, p < 0.001), and in individuals with an abnormal ECG according to the International Recommendations for ECG interpretations in Athletes compared to those with ECGs which would be considered normal (17% vs 3%, p < 0.001) .1
Five (3%) individuals required cardiac intervention including 3 individuals who underwent percutaneous ASD closure, 1 individual implanted with a primary prevention implantable cardioverter defibrillator for a diagnosis of Brugada syndrome and 1 individual implanted with a permanent pacemaker for progressive cardiac conduction disease.
Conclusion The prevalence of CRBBB in a large cohort of young individuals was 0.1% which is similar to large observational studies of the general population. CRBBB-related cardiac conditions were identified in 5% of young individuals with CRBBB and were more likely in individuals with non-isolated CRBBB. These findings highlight the clinical significance of CRBBB in young individuals and suggest that secondary cardiac evaluation should be considered for all young individuals with CRBBB, but particularly those with CRBBB and associated symptoms or additional ECG anomalies.
ECG findings considered in non-isolated complete right bundle branch block. CRBBB = complete right bundle branch block. * Definition according to 2017 International recommendations for ECG Interpretation in Athletes.1
Characteristics of individuals identified with complete right bundle branch block at screening. AF: atrial fibrillation; ASD: atrial septal defect; AV: atrioventricular; BrS: Brugada Syndrome; CRBBB: complete right bundle branch block; ECG: 12-lead electrocardiogram; Ms: millisecond; PCCD: progressive cardiac conduction disease. * Definition according to 2017 International recommendations for ECG Interpretation in Athletes.1
Clinical outcomes of individuals with complete right bundle branch block referred for secondary evaluation.
Complete right bundle branch block-related cardiac conditions identified in individuals with isolated and non-isolated complete right bundle branch block.
Conflict of Interest None