Factors Influencing Cardiorespiratory Fitness in Adolescents with Fontan Circulation

Overview

This study investigated the determinants of cardiorespiratory fitness (CRF) in adolescents with Fontan circulation, focusing on hemodynamic and pulmonary variables. Key findings revealed that elevated ventricular end-diastolic pressure (VEDP), transpulmonary pressure gradient (TPG), impaired pulmonary diffusing capacity, and somatic growth parameters significantly influence CRF in this population.

Background

Fontan circulation is a palliative surgical approach for univentricular congenital heart defects, resulting in unique hemodynamic challenges due to the absence of a subpulmonary ventricle. This physiology leads to exercise intolerance, primarily driven by preload limitations, ventricular dysfunction, and elevated pulmonary vascular resistance. Cardiorespiratory fitness, measured by peak oxygen uptake (V̇O₂peak), is a critical prognostic marker linked to morbidity and mortality in these patients. Pulmonary function abnormalities and exercise oscillatory ventilation (EOV) further complicate the clinical picture, with inconsistent associations reported in pediatric cohorts.

Data Highlights

Key Findings

• Elevated ventricular end-diastolic pressure (VEDP) is independently associated with reduced cardiorespiratory fitness in adolescents with Fontan circulation.
• Higher transpulmonary pressure gradient (TPG), indicative of increased pulmonary vascular resistance, correlates with lower peak oxygen uptake.
• Impaired pulmonary diffusing capacity (DLCO/VA) is linked to diminished exercise capacity, highlighting pulmonary contributions to CRF limitations.
• Somatic growth, particularly height, is a significant determinant of V̇O₂peak, emphasizing the role of body size in fitness assessment.
• Exercise oscillatory ventilation (EOV) prevalence was characterized, with exploration of its physiological correlates in this cohort.

Clinical Implications

Assessment of ventricular filling pressures and pulmonary vascular resistance via invasive hemodynamics can provide valuable prognostic information regarding exercise capacity in adolescents with Fontan circulation. Pulmonary function testing, including diffusing capacity measurements, should be integrated into routine evaluations to identify contributors to reduced fitness. Recognizing the impact of somatic growth on CRF underscores the need for individualized interpretation of exercise testing results in this population.

Conclusion

This comprehensive analysis highlights the multifactorial determinants of cardiorespiratory fitness in adolescents with Fontan circulation, emphasizing the interplay between ventricular diastolic function, pulmonary vascular resistance, pulmonary diffusion abnormalities, and somatic growth. These insights can guide tailored clinical management and risk stratification to improve long-term outcomes.

References

1. Norwegian Fontan Project / Oslo University Hospital / 2015-2018 -- Factors Affecting Cardiorespiratory Fitness in Adolescents with Fontan Circulation