[1] Univ Toronto, Labatt Family Heart Ctr, Toronto, ON, Canada
[2] Stanford Univ, Div Pediat Cardiol, Stanford, CA USA
[3] Seattle Childrens Hosp, Div Pediat Cardiol, Seattle, WA USA
[4] Childrens Med Ctr, Div Cardiol, Dallas, TX 75235 USA
[5] Childrens Hosp New York Presbyterian, New York, NY USA
[6] Great Ormond St Hosp Sick Children, Div Cardiol, London WC1N 3JH, England
[7] Univ Alabama, Dept Surg, Birmingham, AL 35294 USA
[8] Johns Hopkins Univ Hosp, Div Pediat Cardiol, Baltimore, MD 21287 USA