1. Division of Cardiac Electrophysiology, Virginia Commonwealth University Pauley Heart Center, Richmond (A.S., J.K., G.K., S.K.P., R.K.S., J.N.K., K.A.E.).
2. Division of Cardiac Electrophysiology, Rush University Medical Center, Chicago, IL (N.J.S., R.Z., R.T., P.S.S.).
3. Medtronic Inc, Minneapolis, MN (S.C., W.B.W., T.J.S.).
4. Division of Cardiac Electrophysiology, Geisinger Heart Institute, Wilkes Barre, PA (P.V.).