1. Department of Medicine, Mayo Clinic, Rochester, MN (S.K., P.N.).
2. Department of Medicine, Cleveland Clinic, OH (M.C.).
3. Department of Medicine, Kansas City Heart Rhythm Institute, Overland Park (R.G.).
4. Department of Medicine, University of Wisconsin, Madison (L.E., M.L.).
5. Department of Medicine, Columbia University, New York, NY (E.W.).
6. Department of Medicine, Stanford University, CA (P.J.W.).