1. From the Division of Cardiovascular Diseases (P.A.F., T.M.M.) and the Division of Biostatistics (R.L.M., W.R.B.), Mayo Clinic, Rochester, Minn; Electrophysiology, Trinity Medical Center, Rock Island, Ill (H.A.); Electrophysiology and Cardiac Pacing, Austin Heart, Austin, Tex (D.K.); Cardiology/Electrophysiology, Watson Clinic, Lakeland, Fla (N.G.K.); Internal Medicine/Cardiology, Virginia Commonwealth University, Richmond (M.W.); Cardiovascular Disease, MidWest Research Foundation, Riverside...