1. From the Pediatric Heart Center (P.S.M., S.E.G.H., T.R.K., D.T., S.P.M.) and Departments of Neurology (M.J.P., A.J.B., S.P.M.), Radiology (A.J.B.), Epidemiology (D.V.G.), and Biostatistics (D.V.G.), University of California, San Francisco, and the Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada (S.P.M.).