1. Division of Cardiovascular Medicine, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia (A.S., R.D.S., F.E.M., B.D., B.N., D.S.F.).
2. Section of Cardiac Electrophysiology, Emory University School of Medicine, Atlanta, GA (R.I., M.L., N.K.B., F.M.M.).
3. Knight Cardiovascular Institute, Oregon Health and Science University, Portland (L.A., B.N.).
4. Division of Cardiovascular Medicine, Cardiac Electrophysiology Section, University of Colorado Anschutz Medical Campus, Aurora (J.A., W.T.).