1. Cardiovascular Research Center, Massachusetts General Hospital, Boston (J.R., A.S.).
2. Department of Internal Medicine (Cardiology) (J.A.H.), University of Texas Southwestern Medical Center, Dallas.
3. Department of Molecular Biology (J.A.H.), University of Texas Southwestern Medical Center, Dallas.
4. Whitaker Cardiovascular Institute, Boston University School of Medicine, MA (M.V.-M., F.S.).