Important advances in cardiac surgery, intensive care, and diagnostic modalities over the last decades have led to a steady growth in the number of adults with congenital heart defects. Among adults with congenital heart disease, patients with a Fontan circulation typically show the lowest values of peak oxygen consumption. For these patients, strict exclusion from activities at high altitude may have an impact on quality of life. The investigators aim to elucidate the short term effects of a stay at high altitude on hemodynamic adaptation, exercise capacity and clinical well being in adult Fontan patients. The investigators hypothesize that patients with a Fontan circulation in NYHA functional class I-II are able to increase their cardiac output during exercise at high altitude in order to meet the required metabolic demands and therefore tolerate the journey to the Jungfraujoch well.

Background:

Important advances in cardiac surgery, intensive care, and diagnostic modalities over the last decades have led to a steady growth in the number of adults with congenital heart defects (Grown-up congenital heart disease GUCH). Among adults with congenital heart disease, patients with a Fontan circulation typically show the lowest values of peak oxygen consumption with peak VO2 values between 15 and 29 ml/kg/min, corresponding to 43-64 % of the predicted values in healthy controls. For these patients, strict exclusion from activities at high altitude may have an impact on quality of life. Unfortunately, the most recent recommendations for physical activity, recreation sport, and exercise training in paediatric patients with congenital heart disease do not provide specific recommendations. The investigators study therefore aims to elucidate the short term effects of a stay at high altitude on hemodynamic adaptation, exercise capacity and clinical well being in adult Fontan patients. These results are necessary to counsel GUCH patients with respect to their leasure activities in Switzerland.

Objective:

The aims of the study are to measure a)the hemodynamic adaptation (pulmonary blood flow) at rest and during exercise; b)the response of cardiopulmonary parameters to exercise (ventilation, O2 uptake) and c) heart rate variability and occurrence of arrhythmias during the journey and while performing study measures in patients with a Fontan circulation. The measurements will be performed at high altitude and at lowland and compared with an age- and gender-matched control group of healthy subjects. The objective is to test the clinical tolerance of high altitude exposure after a rapid ascent with public transport in patients with a Fontan circulation. The investigators hypothesize that patients with a Fontan circulation in NYHA functional class I-II are able to increase their cardiac output during exercise at high altitude in order to meet the required metabolic demands despite hypoxia induced pulmonary vasoconstriction and therefore tolerate the journey to the Jungfraujoch well.

Methods:

The investigators aim to include 30 patients with a Fontan circulation and 30 age and gender-matched healthy adults. Baseline testing in Bern (540m over sea level)includes: a symptom limited cardiopulmonary exercise stress test on a cycle ergometer with a ramp protocol (CPX); a pulmonary function test (spirometry); a symptom limited, stepwise increasing workload test with non-invasive inert gas rebreathing method for pulmonary blood flow measurement during exercise (Innocor®); analysis of heart rate variability (HRV); Holter-ECG monitoring for detection of arrhythmias.

Within a time period of 12 weeks, the baseline tests will be repeated on the Jungfraujoch (3454m).

The primary endpoint of this study is the increase of pulmonary blood flow during exercise in response to high altitude exposure.

Inclusion Criteria:

• Age above 18years
• Congenital heart disease and Fontan circulation
• NYHA functional class I & II
• Peak VO2 > 45% of predicted
• Signed informed consent

Exclusion Criteria:

• "Failing Fontan", peak VO2 < 45% of predicted
• Significant right-to-left shunt
• Baseline arterial O2 saturation at rest <90% at room air
• Hospitalization within the last 3 months for cardiac reasons
• Decrease in functional NYHA class within the last 3 months
• Motor skill inability to perform a maximal exercise stress test
• Respiratory Exchange Ratio < 1
• Pregnancy