1. From Division of Cardiology (R.T.C., P.M.W.) and Departments of Pathology and Laboratory Medicine (T.R.B., D.S.H., P.M.W.) and Radiology (P.M.W.), the Children’s Hospital of Philadelphia, Philadelphia, Pa; and the University of Pennsylvania School of Medicine (R.T.C., D.S.H., P.M.W.), Philadelphia, Pa.