1. University College London Institute of Cardiovascular Science, London, United Kingdom (C.J.C., P.S., T.A.T., J.C.M., L.R.L., C.G.A.M., W.J.M., P.M.E.)
2. University College London Great Ormond Street Institute of Child Health, London, United Kingdom (C.J.C., W.E.H., N.A., K.M.)
3. Histopathology Unit, Great Ormond Street Hospital for Children, London, United Kingdom (A.V., M.A., N.J.S.)
4. Department of Anatomy and Histology, Bosch Institute, The University of Sydney, New South Wales, Australia (C.d.R.).
5. Barts Heart Centre, Barts Health NHS Trust, London, United Kingdom (T.A.T., J.C.M., L.R.L., P.M.E.).