1 Cardiac Intensive Care Unit, Department of Nursing, Respiratory Care and Neurodiagnostic Services, The Children's Hospital of Philadelphia, Philadelphia, PA; Department of Cardiology, Boston Children's Hospital, Boston, MA; Department of Pediatrics, Harvard Medical School, Boston, MA; and Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA; Department of Cardiology, Boston Children's Hospital, Boston, MA; Ellen and Robert Kapito Professor of Nursing Science, Department of Family and Community Health in the School of Nursing at the University of Pennsylvania, Philadelphia, PA; and Department of Anesthesia and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.