Electrocardiographic right and left bundle branch block patterns in athletes: Prevalence, pathology, and clinical significance

• Typical complete RBBB may be an ECG marker of physiologic athletic cardiac remodeling.
• Atypical RBBB in athletes suggests the presence of structural or electrical cardiac pathology and should prompt comprehensive evaluation.
• LBBB in athletes is unrelated to exercise physiology and warrants thorough clinical investigation.
• Long-term cardiovascular outcomes of athletes with both RBBB and LBBB are unknown.

Differentiating benign electrocardiographic (ECG) patterns in athletes from those representative of underlying cardiac pathology is both clinically relevant and challenging. Complete right (RBBB) and left (LBBB) bundle branch block are relatively rare in asymptomatic athletic populations, and current expert consensus guidelines recommend further clinical investigation upon detection of either ECG pattern. However, present data suggest that typical RBBB is not associated with structural cardiac pathology and may alternatively represent an ECG marker of exercise-induced right ventricular remodeling. In accordance with current guidelines, the presence of asymptomatic LBBB in athletes is not associated with normal exercise physiology and more likely indicative of underlying cardiac pathology. While long-term outcomes for asymptomatic athletes with RBBB or LBBB remain unknown, current evidence regarding these ECG patterns should be considered to improve the specificity of future athlete-specific ECG interpretation guidelines.