From the Department of Pediatrics, New England Medical Center, Tufts University School of Medicine, Boston, Mass (HCM, HLD); Children's Hospital, Buffalo, NY (RCW); Creighton University School of Medicine, Omaha, NE (SAC); University of Manitoba, Winnipeg, Manitoba, Canada (BJL); Baylor College of Medicine, Houston, TX (LEW); and Children's Hospital National Medical Center, Washington, DC (WJR).