1. Department of Cardiology (C.B., M.d.R., K.Z.), Leiden University Medical Center, the Netherlands.
2. Center for Electrophysiology, Bremen, Germany (J.H., J.-H.N.).
3. Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark (P.L., J.C.N.).
4. Department of Pediatric Cardiology (N.B.), Leiden University Medical Center, the Netherlands.
5. Department of Cardiothoracic Surgery, Leiden University Medical Center, the Netherlands (M.H).