Exercise responses in children and adults with a Fontan circulation at simulated altitude

Background: Traveling to high altitude has become more popular. High-altitude exposure causes hypobaric hypoxia. Exposure to acute high altitude, during air travel or mountain stays, seems to be safe for most patients with congenital heart disorders (CHD). Still, current guidelines for CHD patients express concerns regarding safety of altitude exposure for patients with a Fontan circulation. Therefore, investigating hemodynamic and pulmonary responses of acute high-altitude exposure (±2500 m) at rest and during maximal exercise in patients with Fontan circulation can provide clarity in this dispute and may contribute to improvement of clinical counseling. Methods: Twenty-one Fontan patients with 21 age-matched healthy controls, aged 8-40 years, were enrolled in an observational study. Participants performed two cardiopulmonary exercise tests on a cycle ergometer with breath-by-breath respiratory gas analyses combined with noninvasive impedance cardiac output measurements: one at sea level (±6 m) and one at simulated high altitude (±2500 m), respectively. Results: The effect of altitude exposure was different in rest for saturation (−2.3% vs −4.1%) between Fontan patients and healthy controls (P <.05). At peak exercise the effects of high altitude exposure was different on VO ₂ (−5.1% vs 9.6%) and AvO ₂-diff (−0.3% vs −12.8%) between Fontan patients and healthy controls. Conclusion: Although, acute high-altitude exposure has a detrimental effect on exercise capacity, the impact on pulmonary and hemodynamic responses of high-altitude exposure is comparable between Fontan patients and healthy controls.