Cardiorespiratory Fitness in Paediatric Congenital Heart Disease

Abstract

The aims of the current thesis were to: 1) assess the association between peak oxygen consumption (peak V̇O2) to mortality and morbidity in people with congenital heart disease (ConHD); 2) assess the validity of peak V̇O2 as a marker for cardiorespiratory fitness in people with ConHD; 3) evaluate the effectiveness of physical activity interventions in improving peak V̇O2; and 4) to explore the external factors that may influence young people with ConHD participating in physical activity. Study one (Chapter 4) used a systematic review and meta-analysis methodology to identify that peak V̇O2 (scaled by body mass or expressed as a percentage of predicted value [%Pred]) was a significant prognostic factor in people with ConHD (Hazard ratio [HR] 0.88, 95% CI 0.83 to 0.93). Studies 2 and 3 (Chapter 5 and 6) demonstrated peak V̇O2 scaled by body mass or expressed as a %Pred (derived from the recommended reference equations) were invalid when applied to people with complex ConHD. Furthermore, study 2 (Chapter 5) reported that peak V̇O2 scaled to measures of fat-free mass (FFM) or lean mass (LM) were valid expressions of cardiorespiratory fitness as they were body size-and-composition independent (FFM r=0.11, 95% CI -0.12 to 0.33; LM r=0.08, 95% CI -0.13 to 0.29). Study 4 (Chapter 7) confirmed that peak V̇O2 scaled to FFM or LM were significantly associated to mortality and morbidity in people with ConHD (peak V̇O2 mL·FFM-1·min-1 HR 0.90, 95% CI 0.82 to 0.99; peak V̇O2 mL·LM-1·min-1 0.90, 95% CI 0.83 to 0.98). For every one-unit increase in peak V̇O2 scaled to either FFM or LM there was a 10% reduction in the risk of Fontan failure. Study 5 (Chapter 8) synthesised the available randomised control trial (RCT) evidence using a systematic review and meta-analysis and reported that with moderate certainty, physical activity interventions, in particular exercise training, improved peak V̇O2 (mean difference 1.89 mL·kg-1·min-1, 95% CI -0.22 to 3.99; 14 RCT) with zero serious iv adverse events reported. Finally, study 6 (Chapter 9) reported that parents of young-people with ConHD are significant enablers of their children’s physical activity behaviours and a qualitative theme of “knowledge is power and comfort” emerged as parents were uncertain about what activities are appropriate for their children, due to a lack of and inconsistent advice from health professionals. In conclusion, the current thesis challenges current practices regarding the scaling and interpretation of peak V̇O2 in people with ConHD. It is recommended that in future clinical practice and research that peak V̇O2 should be scaled to measures of body composition, as this valid fitness metric is significantly associated to Fontan failure. Furthermore, the thesis reports that peak V̇O2 can be improved in people with ConHD with very low risks of serious adverse events and that clinical teams should be providing individualised physical activity advice to children and families who have ConHD