1. From the Department of Pediatrics, Division of Pediatric Cardiology (G.H., S.S., V.A.D.J.P., T.U., L.W., M.R.), Department of Medicine, Division of Cardiovascular Medicine (R.A.W.), and Department of Cardiovascular Surgery (A.Y.S.), Stanford University School of Medicine, Stanford, Calif, and Department of Medicine, Division of Cardiology, University of Toronto, Toronto, Ontario, Canada (R.S.S., D.J.S.).