1. From the Department of Cardiac Electrophysiology, Hammersmith Hospital, Imperial College Healthcare Trust, London, United Kingdom (S.J.-C., N.L., M.K.-W., V.L., D.P.F., N.S.P., D.W.D., P.K.); Arrhythmology and Cardiac Electrophysiology Division, San Raffaele Hospital, University of Milan, Milan, Italy (P.V., P.D.B.); and Department of Arrhythmology and Electrophysiology, Centro Cardiologico Monzino, Milan, Italy (C.C., C.T.).