1. Department of Pediatrics, Labatt Family Heart Centre (G.E.P., L.G.-W., M.H., M.F., P.C., C.S., W.H., C.-P.S.F., C.M., L.M., R.H., M.K.F.), Hospital for Sick Children, University of Toronto, ON, Canada.
2. NIHR Cardiovascular Biomedical Research Centre, Bristol Heart Institute, United Kingdom (G.E.P.).
3. Department of Diagnostic Imaging (L.G.-W.), Hospital for Sick Children, University of Toronto, ON, Canada.
4. Department of Pediatrics (L.G.-W.), Hospital for Sick Children, University of Toronto, ON, Canada.