Effects of exercise training, with or without supplemental oxygen, in adults with complex congenital heart disease

Background: The number of adults with complex congenital heart disease (ACHD) is increasing and patients are living longer with the condition; therefore, there is a need to investigate lifestyle factors and assess the physical fitness of these patients and to prescribe exercise. We aimed to evaluate the effects of exercise, with or without supplemental oxygen, in patients with complex ACHD. Methods: Between August 2018 and December 2019, 35 patients were assessed and eight were included in the study. A randomized crossover design was used, and participants were randomized to start exercising with supplemental oxygen (OxyStart) or without (OxyEnd). Muscle function, maximal oxygen uptake (VO2peak), walking distance, physical activity level, patient-reported outcome measures, and blood parameters were assessed. Results: Four participants were randomized to the OxyStart group (n = 4) and four to the OxyEnd group (n = 4). No-one dropped out of the OxyStart group, but two patients dropped out of in the OxyEnd group. Exercise training resulted in improvements in VO2peak (Δ +1.9 ​ml/kg/min), three of four tests of muscle function, walking distance (Δ +97.5 ​m), and patient-reported outcome measures in participants who completed the study (n ​= ​6). No adverse events occurred during exercise. However, the participants showed diverse responses to oxygen supplementation. Conclusion: Patients with complex ACHD benefit from peripheral muscle function exercises. Exercise with supplemental oxygen appears to be safe for such patients but may not affect patients with differing ACHD etiology uniformly; therefore, further studies are required to investigate this.