[1] Hosp Sick Children, Div Cardiol, Toronto, ON M5G 1X8, Canada
[2] Harvard Univ, Sch Med, Childrens Hosp Boston, Boston, MA USA
[3] Indiana Univ, Sch Med, Indianapolis, IN USA
[4] Cincinnati Childrens Hosp Med Ctr, Cincinnati, OH USA
[5] Childrens Hosp Eastern Ontario, Ottawa, ON K1H 8L1, Canada
[6] Univ Klinikum Munster, Med Klin & Poliklin C, Munster, Germany
[7] Oregon Hlth & Sci Univ, Portland, OR USA
[8] Stanford Univ, Palo Alto, CA 94304 USA
[9] Washington Univ, Sch Med, St Louis, MO USA
[10] Columbus Childrens Hosp, Columbus, OH USA
[11] Rigshosp, Hjertectr, DK-2100 Copenhagen, Denmark