1. Department of Cardiology, University Medical Centre Utrecht, the Netherlands (P.L., R.v.E., M.H.A.G., W.K., F.H.M.W., P.A.D.).
2. Department of Electrophysiology, Alfried Krupp Krankenhaus, Essen (K.N.).
3. Witten/Herdecke University, Germany (K.N.).
4. Netherlands Heart Institute, Utrecht (P.A.D.).