[1] Alfred I DuPont Hosp Children, Nemours Cardiac Ctr, Wilmington, DE 19803 USA
[2] Northwestern Univ, Dept Prevent Med, Chicago, IL 60611 USA
[3] NHLBI, Bethesda, MD 20892 USA
[4] Univ Colorado, Denver, CO 80202 USA
[5] Univ Alabama Birmingham, Dept Med, Birmingham, AL USA
[6] Hackensack Univ Med Ctr, Dept Med, Hackensack, NJ USA
[7] Johns Hopkins Univ Hosp, Dept Med, Baltimore, MD USA