Sport Type Alone Does Not Reliably Predict Distinct Cardiac Phenotypes in Athletes

: Sport-type classification frameworks recommended by European (ESC) and American (AHA/ACC) guidelines are used to contextualize cardiac remodelling in athletes but remain unvalidated against cardiac magnetic resonance (CMR) phenotypes. We aimed to evaluate whether sport classifications predict CMR-determined cardiac remodelling phenotypes in elite athletes.

: We included 1,024 individuals: 775 elite athletes (310 women, 48 disciplines) and 249 controls. Athletes were classified by the ESC (four-category) and AHA/ACC (static-dynamic, four-quadrant) frameworks. CMR metrics were transformed to sex-specific z-scores (remodelling: z≥1.645). Because no CMR convention defines geometric phenotypes in athletes, the most strongly associated CMR metric was used to define each framework's assumed phenotype. Performance was evaluated at population (R2) and individual (balanced accuracy) levels. ESC categories were most strongly associated with RVEDV (R2=0.170); RV remodelling prevalence increased from skill to endurance (8.3%-62.2%; OR 3.82 per category; P<0.001). The AHA/ACC static component was most strongly associated with LV mass (R2=0.077) and the dynamic component with RVEDV (R2=0.072). Individual-level discrimination was poor: balanced accuracy was 34.2% (ESC) and 37.7% (AHA/ACC) (vs 25% chance). LV mass and RVEDV showed coupled increases (R2=0.23), with 67% of athletes demonstrating concordant patterns rather than discrete static or dynamic phenotypes. Misclassification was most pronounced for predominantly high-static athletes, of whom 73.8% showed normal geometry rather than expected LV hypertrophy (17.5%).

: ESC and AHA/ACC sport classifications capture population-level remodelling but cannot reliably be used to predict individual cardiac phenotypes. In individual athletes interpretation should prioritise observed mass-volume relationships and the overall clinical context rather than sport type alone.