How well can wearables in children and adolescents with congenital heart disease represent their exercise capacity?

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Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Stiftung KinderHerz Background Wearables enjoy great popularity in children and adolescents. They suggest objectively measuring subjects’ physical activity (PA) or at least give a hint of how it is. But is there a correlation between step-count, moderate to vigorous physical activity (MVPA), and peak oxygen uptake (peakV’O2)? Purpose This study investigates this question in children with various congenital heart diseases (CHD). Methods From September 2017 to September 2021 sixty-six patients (13 ± 3 years, 20 girls) measured their daily step-count and MVPA via Garmin fit jr. over one week and underwent a cardiopulmonary exercise test (CPET) to quantify their peakV’O2. CHD severity was complex in 50%, moderate in 39%, and simple in 11%. The distribution consisted of 18% with a left heart defect, 50% with a right heart defect, 5% with a Fontan circulation, 9% with an isolated shunt, and 18% with transposition of the great arteries. The correlation was performed via first Spearman’s correlation and secondly partial correlation, adjusted for age, sex height, and weight. Results are presented in median [IQR25;IQR75]. Results Median steps on a weekly average were 7,576 [6,100;10,888] and MVPA 68 [52;95] minutes. PeakV’O2 was 33 [28;39] ml/min/kg, represented as 77 [68;91] % of predicted, which corresponds to slight impairment. Step-counts slightly correlates with peakV’O2 (r=0.277, p=0.024). However, correlation vanished after adjusting for anthropometrics (step-count: r=0.244, p=0.056). MVPA and peakV’O2 did not correlate at all. Conclusions Objectively measured PA and exercise capacity are poorly associated. Since both are independent constructs, it is necessary to assess both in a clinical setting - PA in the context of cardiovascular prevention and peakV’O2 as the strongest predictor for morbidity and mortality.