1. Center for Congenital Heart Diseases, Division of Pediatric Cardiology, Beatrix Children's Hospital; University of Groningen, University Medical Center Groningen; 9713 AV Groningen The Netherlands
2. Department of Cardiology; University of Groningen, University Medical Center Groningen; Groningen The Netherlands
3. Departments of Cardiology and Cardiothoracic Surgery; Leiden University Medical Center; Leiden The Netherlands