1. From the Centre for Cardiovascular Imaging, University College London Institute of Cardiovascular Science, London, United Kingdom (A.M.T., S.S., S.T.); Cardiorespiratory Services, Great Ormond Street Hospital for Children (A.M.T.), Department of Histopathology, University College London Institute of Child Health and Great Ormond Street Hospital for Children (N.J.S., M.T.A.), and Department of Histopathology, University College London Hospitals (R.J.S.), National Health Service Foundation Trust,...