1. From the Department of Medicine (A.F.B., N.N., S.S., K.A.R.) and Cardiac Pacing and Electrophysiology Section (O.M.W., K.G.T., T.C., W.I.S., J.R., M.P.B., D.O.M., M.K., B.B., D.C., M.N., T.D., B.D.L., B.L.W., A.A.H.), Heart and Vascular Institute, Cleveland Clinic, OH.