The upper limit of physiological cardiac remodelling in highly trained elite athletes: concepts revised by CMR

Abstract Background Elite athletes, especially endurance ones, show a high level of cardiac adaptation, making it challenging to differentiate physiological from pathological remodelling. Cardiac magnetic resonance (CMR) indication for this scope is growing rapidly; however, cohorts enrolled to define normal values suffer from limitations, as they are not explicitly selected for the absence of cardiovascular abnormalities. Objective to explore the highest spectrum of cardiac adaptation in elite athletes by CMR and provide reference values for high-level athletes. Methods 320 Olympic athletes from all the sports categories as defined by ESC classification were enrolled (mean age 26±4 years, 58% males, 13% skill, 18% power, 29% mixed, 40% endurance). They underwent a cardiovascular evaluation (comprising a basal blood test, clinical evaluation, ECG, a maximal stress test, and echocardiography) before enrollment, which did not reveal any cardiovascular abnormalities. Subsequently, they voluntarily underwent CMR without contrast administration. CMR cine-loops were post-processed to obtain left ventricular (LV) and right ventricular (RV) volumes, mass and ejection fraction (EF). Differences between sports categories and male vs. female athletes were investigated. Results The main parameters for male and female athletes are shown in the Tables. The population was homogeneous concerning the amount of training and BSA (Tables). Endurance athletes, as expected, showed the greatest cardiovascular adaptation in terms of LV and RV volumes both for male (p0.001 for both) and female athletes (p 0.001 for both). No differences were found in LV and RV EF among athletes of different sports categories (p= 0.953 and p= 0.981 for males; p= 0.159 and p= 0.111 for females). Most importantly, male and female endurance athletes showed significantly higher LV mass and interventricular septum (IVS) thickness than other athletes. Still, the upper limit of IVS thickness was 13 mm in males and 11 mm in females (Figure). Finally, only a small minority showed LVEF 50% (1%) and RVEF 50% (2%), most of whom were cyclists. Conclusion Our work describes CMR-derived cardiac adaptation in a population of Olympic athletes specifically selected without CV abnormalities, providing reference values for both LV and RV parameters across all the ESC sports disciplines. Both male and female endurance athletes showed the greatest biventricular remodelling, but there were no differences in biventricular ejection fraction between athletes of different sports categories. Virtually none of the athletes had an LV EF lower than 50%, and the majority of those showing were cyclists. The highest myocardial thickness was lower than currently known, suggesting that the definition of the grey zone should be revised, at least in Caucasian athletes.