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