1. Cleveland Clinic Heart and Vascular Institute, Ohio (L.C., F.B.,T.K.).
2. University of North Caroline Medical School, Chapel Hill (M.R.K.).
3. Mayo Clinic, Rochester, MN (N.R.A.).
4. University of Michigan Medical School, Ann Arbor (M.B.D.).
5. Johns Hopkins University Medical School, Baltimore, MD (J.S.L.).
6. University of Toronto Medical School, Canada (M.O.).
7. Baylor University Medical School, Dallas, TX (O.P.).
8. Cooper University Hospital, Camden, NJ (A.M.R.).
9. Renaissance School of Medicine, Stony Brook, NY (A.-L.W.S.).
10. Duke University Medical School, Durham, NC (B.A.Z.).
11. Washington University Medical School, St Louis, MO (K.J.L.).