1. Department of Medicine; The Johns Hopkins University; Baltimore Maryland
2. Department of Pediatrics; The Johns Hopkins University; Baltimore Maryland
3. Division of Pediatric Oncology; The Johns Hopkins University; Baltimore Maryland
4. Department of Epidemiology; The Johns Hopkins Bloomberg School of Public Health; Baltimore Maryland
5. Division of Pediatric Cardiology; The Johns Hopkins University; Baltimore Maryland
6. Division of Cardiology; Section for Cardiac Electrophysiology; The Johns Hopkins University; Baltimore Maryland
7. Division of Cardiology; Section for Cardiac Electrophysiology; Hospital of the University of Pennsylvania; Philadelphia Pennsylvania