Adequate exercise response at artificial altitude in Fontan patients

Area of Science:

• Cardiology
• Exercise Physiology
• Pediatric Cardiology

Background:

• Fontan-palliated patients face uncertainties regarding altitude exposure effects on cardiac output during exercise.
• Hypoxic pulmonary vasoconstriction's impact on cardiac function in Fontan physiology remains unclear.

Purpose of the Study:

• To investigate the effects of simulated altitude (normobaric hypoxia, 2,500 m) on cardiopulmonary and metabolic parameters in Fontan patients.
• To assess the benefit of daily physical activity (PA) on exercise capacity under hypoxic conditions.

Main Methods:

• 21 Fontan patients and 20 controls underwent cardiopulmonary exercise tests in normoxia and hypoxia.
• Capillary lactate (cLa) and activity tracking via accelerometer were measured.

Main Results:

• Hypoxic exercise was safe for Fontan patients, with no adverse events.
• Fontan patients exhibited reduced physical capacity but similar relative hypoxic impairment (≈10%) compared to controls.
• Oxygen uptake ($$ O₂), heart rate (HR), and cardiac output (Qc) were comparable up to 2 W/kg workloads.
• Higher daily PA correlated with improved $$ O_2p in hypoxia.

Conclusions:

• Short-term simulated altitude exercise is safe for young Fontan patients.
• Oxygen uptake, heart rate, and cardiac output are not limiting factors up to 2 W/kg workloads.
• Increased physical activity may enhance exercise capacity in Fontan patients at altitude.