1. Adult Congenital Heart Centre and Centre for Pulmonary Hypertension, Royal Brompton Hospital, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, London, United Kingdom (K.D., A.C.).
2. National Heart and Lung Institute, Imperial College London, United Kingdom (K.D., A.C.).
3. Department of Cardiology, Queen Elizabeth Hospital Birmingham, United Kingdom (P.C.).
4. Pulmonary Vascular Disease Unit, Royal Hallamshire Hospital, Sheffield, United Kingdom (R.C.).
5. National Paediatric Pulmonary Hypertension Service UK, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom (S.M.).
6. Institute of Cardiovascular Science, University College London, United Kingdom (S.M.).
7. Adult Congenital and Paediatric Heart Unit, Freeman Hospital Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom (K.J.).
8. Population Health Sciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom (K.J.).
9. Department of Pediatrics, The University of Tokyo Hospital, Japan (R.I.).
10. Scottish Adult Congenital Cardiac Service, Golden Jubilee Hospital, Glasgow, Scotland, United Kingdom (G.R.V.).
11. The Heart Center, Nationwide Children’s Hospital, Columbus, OH (C.L.C.).
12. Department of Cardiology, National University Hospital Singapore (E.T.L.W.).
13. The Heart Institute, Department of Pediatrics, Cincinnati Children’s Hospital, University of Cincinnati College of Medicine, OH (A.R.O.).
14. Department of Cardiology, AHEPA University Hospital School of Medicine, Aristotle University of Thessaloniki, Greece (G.G.).
15. Division of Cardiology, Toronto General Hospital, University Health Network, Peter Munk Cardiovascular Center, University of Toronto, Canada (R.A.-G.).
16. Toronto Adult Congenital Heart Disease Program, Canada (R.A.-G.).
17. Department of Cardiology, Royal Prince Alfred Hospital and Sydney Medical School, University of Sydney, New South Wales, Australia (R.C.).
18. Down Syndrome Clinical and Research Center, Kennedy Krieger Institute, Baltimore, MD (G. Capone).
19. Johns Hopkins School of Medicine, Baltimore, MD (G. Capone).
20. Department of Paediatric Cardiology, Uganda Heart Institute, Kampala (J.N.).
21. Department of Paediatrics and Child Health, Makerere University College of Health Sciences, Kampala, Uganda (J.N.).
22. University Hospital of the West Indies, Kingston, Jamaica (C.H.S.).
23. Department of Cardiology, University “L. Vanvitelli”–Monaldi Hospital, Naples, Italy (M.D.).
24. Department of Cardiovascular Surgery, Benjamin Bloom Children’s Hospital, El Salvador (F.J.G.).
25. Advocate Medical Group Adult Down Syndrome Center, Park Ridge, IL (B.C.).
26. Department of Pediatric Cardiology, Beijing Anzhen Hospital, Capital Medical University, China (H.G.).
27. Division of Pediatric Cardiology, Department of Pediatrics, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand (A.L.).
28. Department of Cardiology, Euracare Multi-specialist Hospital, Nigeria (T.M.).
29. Division of Congenital and Structural Cardiology, University Hospitals Leuven, and Department of Cardiovascular Science, Catholic University Leuven, Belgium (W.B.).
30. Department of Cardiology, Royal Free Hospital, London, United Kingdom (G. Coghlan).
31. Knight Cardiovascular Institute, Oregon Health and Science University, Portland (C.S.B.).