1. Duke Clinical Research Institute, Duke University, Durham, NC (D.S.C., E.B.-M., Z.L., D.B.M., J.P.P.).
2. Department of Cardiovascular Diseases, Mayo Clinic, Rochester, MN (P.A.N., D.L.P.).
3. Libin Cardiovascular Institute of Alberta, University of Calgary, Canada (D.V.E.).
4. Duke Center for Atrial Fibrillation, Department of Medicine, Duke University Medical Center, Durham, NC (J.P.P.).