1. Division of Cardiology; Children's National Medical Center, George Washington University School of Medicine and Health Sciences
2. Department of Pediatrics; George Washington University School of Medicine and Health Sciences
3. Division of Cardiology; The Children's Hospital of Philadelphia
4. Department of Pediatrics; Perelman School of Medicine, The University of Pennsylvania; Philadelphia
5. Mid America Heart Institute St. Luke's Health System
6. Center for Clinical Epidemiology and Biostatistics; Perelman School of Medicine at the University of Pennsylvania