1. Department of Cardiology, Boston Children’s Hospital, Department of Pediatrics, Harvard Medical School, MA (T.G., K.G., K.H., A.J.P., A.M.V.).
2. Department of Cardiology, Academic Medical Centre, Amsterdam, the Netherlands (B.M.).
3. Royal Brompton and Harefield National Health Service Foundation Trust, National Heart and Lung Institute, Imperial College London, United Kingdom (S.V.B.-N., M.A.G.).
4. Division of Cardiology, University of Toronto, Peter Munk Cardiac Centre, Canada (R.M.W.).