1. Division of Cardiology, Department of Medicine, Duke University School of Medicine, Durham, NC (F.A., S.R.).
2. Cardiovascular Research Center, Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA (T.A.C., P.B.Y.).
3. Johns Hopkins Division of Cardiology, Baltimore, MD (M.M.).
4. Johns Hopkins Division of Pulmonary and Critical Care Medicine, Baltimore, MD (S.C.M.).