1. Inova Heart and Vascular Institute, Falls Church, VA (M.W.S.).
2. Duke Clinical Research Institute, Durham, NC (K.X., R.M., Z.L., S.V., E.D.P.).
3. UPMC Pinnacle, Harrisburg, PA (A.N.V.).
4. Hospital of the University of Pennsylvania, Philadelphia (A.F.).
5. Duke University Medical Center, Durham, NC (J.K.H., S.V.R.).
6. Marcus Heart and Vascular Center, Piedmont Atlanta Hospital, GA (V.H.T.).
7. Mayo Clinic, Rochester, MN (D.H.).
8. NewYork-Presbyterian Hospital, Columbia University Medical Center (A.K.).
9. University of Florida College of Medicine, Jacksonville (A.M.P.).