Abstract Body (Do not enter title and authors here): Objectives:
Physically active lifestyles are important for patients with congenital heart disease, including Fontan. This study aims to establish the effect of an active lifestyle in paediatric Fontan patients, determine its relationship with body composition, exercise capacity, ventricle function and quality of life.

Methods:
30 Fontan patients were recruited. Mean age of 14.8±2 years.
Cardiopulmonary exercise tests, bio-impedance analyser, echocardiography and PedsQL questionnaires, generic (V4.0) and cardiac modules (V3.0) were performed. Physical activity level includes structured sports participation, daily stepcounts, and active-zone-minute, AZM (minute spend doing activity ≥ moderate intensity) measured by accelerometer (Fitbit Inspire3).
Patients were considered active if they met 2 of the 3 criteria:
1/ Structured sports training ≥ 2 per week (moderate-vigorous intensity >30 minutes)
2/ Daily steps ≥ 10k
3/ AZM ≥ 60 minutes per day

Results:
60% of patients were considered active, predominantly male, mean age of 14.1 years old. Overall BMI was normal, however 17% (5 of 30) were overweight or obese (Table 1).

The less active Fontan had higher fat% (24.8±8.7 vs 16.6±5.2%; p=0.003), lower percentage appendicular skeletal muscle mass, SMMa%(29.8±3.6 vs 33.7±3.1%; p=0.004), and muscle to fat ratio, MFR (1.4±0.8 vs 2.3±0.9; p=0.015).

The less active group had lower peak oxygen consumption, VO_2peak (23.5±7.2mL/kg/min vs 35.1±3.96mL/kg/min; p < 0.001), lower peak oxygen pulse (7.9±1.2 vs 10.01±2.9) ml/beat; (p=0.024). No statistical significant differences observed in the ventricle function.

Higher self-report PedQL V4.0 scores noted in the active group, indicated better HRQOL (child’s QOL 88.26±8.6 vs 72.89±17.2%; p=0.003 and parent’s QOL 87.22±10.8 vs 71.6±23.4%; p=0.020).

Higher physical activity level is associated with lower body fat% (r=– 0.521, p=0.003), greater SMMA% (r=0.513, p=0.004), higher peak and submaximal VO2, [VO2/kg peak (r=0.787, p < 0.001) VO2 at ventilatory threshold 1, VT1 (r=0.451, p=0.012)], peak O2pulse (r=0.411, p=0.024), and importantly, higher HRQOL reported [child’s QOL V4.0 (r=0.524,p=0.003), parent’s QOL V4.0 (r=0.423, p=0.020)].

Conclusions:
Higher physical activity levels in paediatric Fontan patients are associated with normal skeletal muscle mass, higher exercise capacity and better HRQOL. Conversely, lower physical activity levels are associated with skeletal muscle mass deficit, increased adiposity and reduced exercise capacity.