 Fontan-palliated patients aged 8-30 will be recruited for this study. Eligible patients will be identified from the cardiology and surgery database here. Patients will be contacted by phone andor formal letter informing them of the study. If their primary cardiologist is not in our group, a courtesy call will be made or letter sent. Age and gender matched healthy controls will be sought as well through local recruitment schools, university campus, local community postings. 