Continuous high training loads are associated with structural cardiac adaptations and development of an athletic heart in adult athletes, especially in sport disciplines with high dynamic training components. In child and adolescent athletes these effects are increasingly reported. However, study populations are still very small. PURPOSE: To determine cardiac dimensions indicating cardiac remodeling in child and adolescent athletes.
METHODS: M Mode echocardiographs of 1021 athletes (m 575, f 446; 8-18 yrs; body surface area (BSA) 0.88-2.0 m²) from 19 sport disciplines were analyzed retrospectively. Sport disciplines were clustered into 9 groups according to Mitchell, categorizing sports by components of dynamic and static training loads. Groups were analyzed separately. Previous organized sporting experience (at least 3-13 yrs) was a requirement for inclusion. Left ventricular diameter (LVEDD), interventricular septal (IVS) and posterior wall (PW) thickness at end-diastole were analyzed and compared to cardiac z Scores (zS) for central European children. Deviations from normal mean (zS = 0) were defined as difference. Data was analyzed descriptively (median ± SD), Bland-Altman analysis was performed. RESULTS: For all analyzed parameters, athletic children and adolescents showed higher median zS though large deviations from the normal mean (zS>1.88) were only seen in single cases. Differences in sport discipline and sex were discovered. Throughout all disciplines, boys showed higher zS compared to girls (LVEDD 0.48±0.96 vs 0.22±0.92; IVS 0.47±0.99 vs 0.29±1.05; PW 0.53±0.76 vs 0.08±0.76), especially in disciplines with high dynamic training loads (Mitchel C I-III). Additionally, high zS were observed in the group of athletes with the highest static and low dynamic training load (Mitchell A III). CONCLUSIONS: Cardiac remodeling in response to athletic training starts at a young age, especially in boys exposed to high dynamic as well as static training loads. The development of zS for young athletes is essential to determine whether zS above the mean in this group are physiological adaptations or the beginning of pathologies. Differences between boys and girls and the high zS in boys with high static training loads indicate an association between fat free mass and cardiac dimensions stronger than BSA.