1. From Department of Clinical Epidemiology (M.Z.L., M.S.O.) and Center for Rare Diseases, Department of Pediatrics (J.R.O.), Aarhus University Hospital, Aarhus N, Denmark; Heart Institute (N.L.M.) and Division of Biostatistics and Epidemiology (J.G.W.), Cincinnati Children’s Hospital Medical Center, Cincinnati, OH; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH (N.L.M., J.G.W.); Heart Center at the Ann & Robert H. Lurie Children’s Hospital of Chicago,...