[1] Childrens Hosp, Neuroepidemiol Unit, Dept Neurol, Boston, MA 02115 USA
[2] Childrens Hosp, Dept Med, Boston, MA 02115 USA
[3] Childrens Hosp, Dept Anesthesia, Boston, MA 02115 USA
[4] Childrens Hosp, Dept Cardiol, Boston, MA 02115 USA
[5] Childrens Hosp, Dept Cardiovasc Surg, Boston, MA 02115 USA
[6] Harvard Univ, Sch Med, Dept Neurol, Cambridge, MA 02138 USA
[7] Harvard Univ, Sch Med, Dept Pediat, Cambridge, MA 02138 USA
[8] Harvard Univ, Sch Med, Dept Anesthesia, Cambridge, MA 02138 USA
[9] Harvard Univ, Sch Med, Dept Surg, Cambridge, MA 02138 USA
[10] Harvard Univ, Sch Publ Hlth, Dept Biostat, Cambridge, MA 02138 USA