Cardiorespiratory response to exercise in children after modified fontan operation

Area of Science:

• Cardiology
• Pediatric Cardiology
• Exercise Physiology

Background:

• The Fontan procedure is a palliative surgery for complex single-ventricle congenital heart defects.
• Long-term exercise function in Fontan survivors is crucial for quality of life and clinical management.
• Understanding exercise limitations is key to optimizing care for these patients.

Purpose of the Study:

• To assess and compare the exercise function of patients who have undergone Fontan repair with that of healthy control subjects.
• To identify specific physiological parameters affected by the Fontan circulation during exercise.

Main Methods:

• Graded treadmill exercise testing was performed on 14 Fontan patients (ages 5.7-17 years) and healthy controls.
• Cardiorespiratory parameters including oxygen uptake (VO2max), anaerobic threshold, heart rate, blood pressure, and oxygen saturation (O2sat) were continuously monitored.
• Spirometry was conducted before and during exercise.

Main Results:

• Fontan patients exhibited significantly reduced peak oxygen uptake (VO2max), anaerobic threshold, and maximal work rate compared to controls.
• Peak minute ventilation, exercise time, and heart rate at peak exercise were also significantly lower in the Fontan group.
• Oxygen saturation (O2sat) dropped significantly during peak exercise in Fontan patients, suggesting potential intrapulmonary shunting.

Conclusions:

• Fontan patients demonstrate markedly reduced aerobic capacity, work capacity, and ventilatory parameters compared to healthy controls.
• The significantly lower anaerobic threshold highlights impaired metabolic response during exercise.
• Decreased oxygen saturation during exercise may indicate intrapulmonary shunting, a known complication affecting oxygenation in Fontan physiology.