1. From the Cardiovascular Research Institute Maastricht, Maastricht, the Netherlands (H.J.W.), and the Department of Cardiology, Electrophysiology and Cardiac Pacing Unit, San Raffaele University Hospital, Milan, Italy (C.P., V.S.)., From the Department of Cardiology, Electrophysiology and Cardiac Pacing Unit, San Raffaele University Hospital, Milan, Italy (C.P., V.S.).