1 Division of Cardiology and Clinical Futures, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; Department of Pediatrics, Perelman School of Medicine at The University of Pennsylvania, Philadelphia, Pennsylvania, USA; Cardiovascular Outcomes, Quality, and Evaluative Research Center, Perelman School of Medicine at The University of Pennsylvania, Philadelphia, Pennsylvania, USA; Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, Pennsylvania, USA. Electronic address: obyrnem@chop.edu.