1. Boston Children’s Hospital and Harvard Medical School, MA (J.W.N., L.A.S., C.D.-M.).
2. Children’s Hospital of Philadelphia and University of Pennsylvania Medical School, Philadelphia (J.W.G.).
3. New England Research Institutes, Watertown, MA (D.H.-P., S.C., P.S.).
4. Children’s Hospital of Wisconsin and Medical College of Wisconsin, Milwaukee (P.C.F., N.S.G.).
5. North Carolina Consortium, Duke University, Durham (J.S.L.).
6. East Carolina University, Greenville, NC (J.S.L.).
7. Wake Forest University, Winston-Salem, NC (J.S.L.).
8. Children’s Healthcare of Atlanta and Emory University, GA (W.T.M.).
9. Morgan Stanley Children’s Hospital of New York-Presbyterian, Columbia College of Physicians and Surgeons, NY (I.A.W.).
10. Medical University of South Carolina, Charleston (A.M.A.).
11. National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (KM.B.).
12. Cincinnati Children’s Medical Center, OH (J.C.).
13. University of Michigan Medical School, Ann Arbor (C.S.G., R.G.O.).
14. Congenital Heart Institute of Florida, St. Petersburg (J.P.J.).
15. Children’s Hospital Los Angeles, CA (A.B.L.).
16. Hospital for Sick Children, Toronto, Ontario, Canada (S.M.).
17. Nemours Cardiac Center, Wilmington, DE (C.P.).
18. Primary Children’s Hospital and the University of Utah, Salt Lake City (A.E.).