1. From the Departments of Cardiology (B.D.S., M.H., A.I., T.G., A.J.P., D.A.G., W.T., G.R.M.) and Anesthesiology (B.D.K.), Children’s Hospital Boston, Boston, Mass, and the Departments of Pediatrics (B.D.S., M.H., A.I., T.G., A.J.P., D.A.G., W.T., G.R.M.) and Anaesthesia (B.D.K.), Harvard Medical School, Boston, Mass.