Exercise Capacity, Endothelial Function, Muscle Mass, and Strength in Pediatric Patients With Fontan Circulation

Fontan circulation carries high morbidity and mortality, driven in part by impaired exercise capacity, muscle deficits, and endothelial dysfunction. In a pediatric cohort with Fontan circulation, we examined associations between exercise capacity, endothelial function, and muscle parameters before enrollment in a randomized exercise intervention.

Patients aged 8-19 years who have Fontan circulation were included. Exclusion criteria included New York Heart Association class IV, active illness, protein-losing enteropathy, pacemaker, or cognitive delay. Assessments included cardiopulmonary exercise testing (peak VO₂), endothelial function testing (reactive hyperemia index [RHI]), fasting lipid profile, dual-energy x-ray absorptiometry and dynamometry (muscle mass and strength), and functional movement screening (FMS).

Among 137 participants (median age 12.7 years; 53% single right ventricle), median time since Fontan was 8.6 years. Peak VO₂ was 1402 ± 509 mL/min (75.7% ± 17.9% predicted; 31.1 ± 7.4 mL/kg/min indexed). RHI was 1.45 ± 0.6; NOx 22.2 ± 17.4 μmol/L. The low-density lipoprotein cholesterol level was 65.8 ± 18.9 mg/dL. Length-adjusted leg lean mass, handgrip strength, and leg extension strength z scores were -1.02 ± 1.0, -0.76 ± 0.9, and -0.70 ± 1.0, respectively. The FMS score averaged 11.9 ± 3.0. Peak VO₂ correlated with RHI (r = 0.50), lnRHI (r = 0.51), FMS (r = 0.30) (all P < 0.001), and length-adjusted leg lean mass z score (r = 0.25, P = 0.003). Indexed and percent-predicted peak VO₂ also correlated with FMS (r = 0.31 and 0.30, respectively) and high-density lipoprotein (r = 0.24 and r = 0.25, respectively).

In youth with Fontan circulation, lower aerobic capacity was associated with lower endothelial function, leg lean mass, strength, and mobility, underscoring the interdependence of cardiovascular, vascular, and musculoskeletal health.

NCT04195451.