1. Department of Medicine, Division of Cardiology, Section of Electrophysiology, St. Elizabeth’s Medical Center, Boston, MA (M.V.O., I.K. M.M., A.E., A.H., J.A., J.V.W.).
2. Department of Medicine, Tufts University School of Medicine, Boston, MA (M.V.O., I.K., J.A., J.V.W.).
3. Abbott Laboratories, Boston, MA (A.J.M.).
4. Boston Scientific, Cardiac Rhythm Management Division, Marlborough, MA (D.C.).