1. Department of Paediatric Cardiology Queen Silvia Children′s Hospital Sahlgrenska University Hospital Gothenburg Sweden
2. Department of Paediatrics Vestfold Hospital Trust Tønsberg Norway
3. Department of Paediatric Cardiology Children's Hospital Helsinki University Central Hospital Helsinki Finland
4. Department of Paediatrics Copenhagen University Hospital Rigshospitalet Denmark
5. Department of Paediatric Cardiology Children′s Hospital Reykjavik Landspitali University Hospital Reykjavik Iceland