1. From the Departments of Cardiology (D.M.H., C.I.B., F.C., T.G., K.G., E.P.W.) and Cardiac Surgery (F.P.), Children’s Hospital Boston, and Departments of Pediatrics (D.M.H., C.I.B., F.C., T.G., K.G., E.P.W.) and Surgery (F.P.), Harvard Medical School, Boston, Mass.