Athlete’s heart represents a structural and functional adaptation to regular endurance exercise.

While left ventricular (LV) hypertrophy of the athlete’s heart has been examined in many studies, the extent of right ventricular (RV) hypertrophy is still uncertain because of its complex shape and trabecular structure. To examine RV hypertrophy, we used magnetic resonance imaging (MRI) and hypothesized that athlete’s heart is characterized by similar LV and RV hypertrophy.

The LV and RV mass, volume, and function in 21 male endurance athletes (A) (27 ± 4 years; 70 ± 8 kg; 178 ± 7 cm; maximal oxygen uptake [Vo₂max]: 68 ± 5 ml/min per kg) and 21 pair-matched untrained control subjects (C) (26 ± 3 years; 71 ± 9 kg; 178 ± 6 cm; Vo₂max: 42 ± 6 ml/min per kg) were analyzed by MRI (Magnetom Vision 1.5T, Siemens, Erlangen, Germany).

Left ventricular masses (A: 200 ± 20 g; C: 148 ± 17 g) and RV masses (A: 77 ± 10 g; C: 56 ± 8 g) differed significantly between the groups (p < 0.001). The LV and RV end-diastolic volumes (EDV) (LV-EDV 167 ± 28 ml [A]; 125 ± 16 ml [C]; RV-EDV 160 ± 26 ml [A]; 128 ± 10 ml [C]), and stroke volumes (SV) (LV-SV: 99 ± 18 ml [A], 74 ± 11 ml [C]; RV-SV: 102 ± 18 ml [A], 79 ± 8 ml [C]) were significantly different between the athletes and control subjects (p < 0.001), whereas ejection fractions (EF) (LV-EF: 59 ± 3% [A]; 59 ± 6% [C]; RV-EF: 63 ± 3% [A], 62 ± 3% [C]) and LV-to-RV ratios were similar for both groups (LV-to-RV mass: 2.6 ± 0.2 [A], 2.6 ± 0.3 [C]; LV-to-RV EDV: 1.05 ± 0.14 [A], 0.99 ± 0.14 [C]; LV-to-RV SV: 0.98 ± 0.17 [A], 0.95 ± 0.17 [C]; LV-to-RV EF: 0.93 ± 0.07 [A], 0.96 ± 0.10 [C]).

Regular and extensive endurance training results in similar changes in LV and RV mass, volume, and function in endurance athletes. This leads to the conclusion that the athlete’s heart is a balanced enlarged heart.