Affiliation: | a Department of Cardiology, Children's National Medical Center, Washington, District of Columbia b Pediatric Cardiology Division, Department of Pediatrics, University of Michigan, Ann Arbor, Michigan c Hematology Division, Department of Pediatrics, University of Michigan, Ann Arbor, Michigan d Pulmonary Division, Department of Pediatrics, University of Michigan, Ann Arbor, Michigan e Pulmonary and Vascular Medicine Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland f Department of Pediatrics and Child Health, Howard University, Washington, District of Columbia g Department of Hematology, Children's National Medical Center, Washington, District of Columbia h Center for Sickle Cell Disease, Howard University College of Medicine, Washington, District of Columbia i Department of Pulmonary, Allergy and Critical Care Medicine and Hemostasis and Vascular Biology Research Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania |