1. From the Division of Cardiology (M.G.-H., N.W.), Brigham and Women's Hospital and Harvard Medical School, Boston, MA; Departments of Cardiology (L.B.S.), Anesthesia (M.E.K., L.B.G.), Genetics (D.T.M.), and Pediatric Oncology (M.W.K.), Children's Hospital Boston and Harvard Medical School, Boston, MA; Division of Pediatric Oncology (M.W.K.) and Department of Biostatistics and Computational Biology (A.S., A.G.-H., D.N.), Dana-Farber Cancer Institute, Boston, MA; Department of Biostatistics (A.S., D.N....