1. From the Adult Congenital Heart Centre and Centre for Pulmonary Hypertension, Royal Brompton Hospital, London, United Kingdom (R.F.-J., A.K., M.P., R.T., A.U., G.-P.D., K.D., L.S., M.A.G.); the Cardiovascular Institute, Hospital Universitario Clínico San Carlos, Madrid, Spain (R.F.-J.); and the Department of Cardiac Surgery (M.A.) and the Department of Medical Imaging (T.M.), Harefield Hospital, London, United Kingdom.