1. From the Harvard-Thorndike Electrophysiology Institute (C.M.T., M.E.J., E.A.) and Cardiovascular Division, Department of Medicine (C.M.T., S.R., R.N., M.E.J., E.A.), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; and Biosense Webster, Johnson & Johnson, Diamond Bar, CA (N.C.D.).