Decreased Muscle Strength in Children With Repaired Tetralogy of Fallot: Relation With Exercise Capacity.

Background The aim of this study is to describe muscle strength in pediatric patients with repaired tetralogy of Fallot compared with healthy peers and to analyze the correlation between muscle strength and peak oxygen uptake, exercise capacity (mL/min). Methods and Results A prospective, cross-sectional study was carried out in the University Medical Center Groningen between March 2016 and December 2019, which included 8 -to-19-year-old patients with repaired tetralogy of Fallot. Exclusion criteria comprised the following: Down syndrome, unstable pulmonary disease and severe scoliosis affecting pulmonary function, neuromuscular disease, and mental or physical limitations that prohibit the execution of the functional tests. Muscle strength was compared with 2 healthy pediatric cohorts from the Northern Netherlands. Handgrip strength, maximal voluntary isometric contraction, and dynamic muscle strength in correlation with peak oxygen uptake, exercise capacity (mL/min) were the main outcomes of the study. The 67 patients with repaired tetralogy of Fallot (42% female; aged 12.9 [interquartile range, 10.0-16.3] years old) were compared with healthy children. The patients showed reduced grip strength (z-score [mean±SD] -1.5±1.2, P<0.001), and total muscle strength (z-score -0.9±1.3, P<0.001). Dynamic strength (Bruininks-Oseretsky test) was significantly reduced (z-score -0.3±0.8, P=0.001), but running, speed, and agility were normal (z-score 0.1±0.7, P=0.4). Univariate correlation analyses showed strong correlations between absolute peak oxygen uptake, exercise capacity (mL/min), and muscle strength (grip strength r=0.83, total muscle strength r=0.88; P<0.001). In multivariate analyses, including correction for age and sex, total muscle strength (B 0.3; P=0.009), and forced vital capacity (B 0.5; P=0.02) correlated with peak oxygen uptake, exercise capacity (mL/min), independent of conventional cardiovascular parameters. Conclusions Children with repaired tetralogy of Fallot show reduced muscle strength, which strongly correlated with their exercise performance.

Six-minute walking distance and decrease in oxygen saturation during the six-minute walk test in pediatric pulmonary arterial hypertension.

OBJECTIVE: To investigate the prognostic value of the 6-minute walking distance (6-MWD), transcutaneous saturation (tcSO2) and heart rate (HR) obtained during the 6-minute walk test (6-MWT) in pediatric pulmonary arterial hypertension (PAH). METHODS: This was an observational study with forty-seven pediatric PAH patients, aged ≥7 years, and diagnosed and followed at the national referral center for pediatric PAH in the Netherlands. All patients performed a comprehensive 6-minute walk test (6-MWT), which measures 6-MWD and tcSO2 and HR before ("baseline"), during ("exercise") and 5 min after ("recovery") the walk test. RESULTS: The 6-MWD expressed either in meters or in sex- and age-corrected z-scores, was associated with transplant-free survival, independently from sex, age, and the presence of a shunt-defect. Shorter 6-MWD correlated with higher WHO-FC and increased NT-pro-BNP. Absolute tcSO2 at exercise and tcSO2-decrease during 6-MWT were associated with transplant-free survival, independent from 6-MWD. Combining tcSO2-decrease with 6-MWD provided the strongest prognostic model. Patients with 6-MWD>352 m (the median 6-MWD) had a better outcome than those with smaller 6-MWD. A large tcSO2-decrease during 6-MWT (>19% for patients with and >5% for patients without a shunt defect) identified patients with worse transplant-free survival both in patients with a 6-MWD above and below the median 6-MWD. CONCLUSIONS: The 6-MWD is an independent predictor of prognosis in pediatric PAH, that reflects disease severity and clinically relevant exercise-tolerance and therefore qualifies as a treatment goal. The magnitude of tcSO2-decrease during 6-MWT, adjusted for the presence of a shunt, indicates an additional risk factor for prognosis in children with PAH.