1. Department of Cardiology, Erasmus Medical Centre, Congenital heart disease RG4, PO Box 2040, 3000 CA, Rotterdam, the Netherlands
2. Department of Cardiology, Antwerp University Hospital, Wilrijkstraat 10, 2650 Edegem, Belgium
3. Department of Cardiovascular Diseases, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium