[1] NHLBI, Div Heart & Vasc Dis, NIH, Bethesda, MD 20892 USA
[2] Childrens Natl Med Ctr, Dept Cardiol, Washington, DC 20010 USA
[3] George Washington Univ, Sch Publ Hlth & Hlth Serv, Ctr Hlth Serv Res & Policy, Forum Collaborat HIV Res, Washington, DC 20006 USA