ObjectivesThis study aimed to provide a perspective for the interpretation of exercise capacity (peakVO2) in patients with repaired Tetralogy of Fallot (patients with rTOF) by describing the course of peakVO2 from patients aged 6–63 years.MethodsA retrospective study was performed between September 2001 and December 2016 in the German Heart Centre Munich, Germany, and in the University Medical Centre Groningen, the Netherlands. A total of 1175 cardiopulmonary exercise tests (CPETs) were collected from 586 patients with rTOF, 46% female. Maximal exertion was verified using a respiratory exchange ratio ≥1.00. PeakVO2 was modelled using time-dependent multilevel models for repeated measurements (n=889 in 300 patients), and compared with subject-specific reference values calculated by the models of Bongers et al and Mylius et al.ResultsThe peakVO2 of patients with rTOF was reduced at all ages. At the age of 6, the peakVO2 was 614 mL/min (70% of predicted (95% CI 67 to 73)). The reduced increase in peakVO2 during adolescence resulted in a significant lower maximum peakVO2 of 1209 mL/min at 25 years (65% predicted, p<0.001). A linear decline after 25 years was observed in patients and references, although patients showed an accelerated decline, with a -0.24% point of predicted (95% CI 0.11 to 0.38) per year without differences between sexes (p=0.263).ConclusionsThis study provides a context for peakVO2 across ages in patients with rTOF under contemporary treatment strategies. It showed that the reduction in peakVO2 originates from childhood and declines over time. Sex differences in patients with rTOF were similar to natural existing sex differences.