[1] Univ Calif Irvine, Dept Med, Div Cardiol, Irvine, CA 92717 USA
[2] Univ Calif Irvine, Dept Med, Div Epidemiol, Irvine, CA 92717 USA
[3] Univ Minnesota, Sch Publ Hlth, Div Epidemiol, Minneapolis, MN 55455 USA
[4] Northwestern Univ, Sch Med, Dept Prevent Med, Chicago, IL 60611 USA
[5] NHLBI, Div Epidemiol & Clin Applicat, Bethesda, MD 20892 USA
[6] AI PuPont Hosp Children, Nemours Cardiac Ctr, Wilmington, DE USA