1. Institute of Clinical Medicine, University of Oslo, Oslo, Norway
2. Division of Paediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
3. Department of Paediatric and Adolescent Medicine, Haukeland University Hospital, Bergen, Norway
4. Department of Clinical Science, University of Bergen, Bergen, Norway
5. Division of Cardiovascular and Pulmonary Diseases, Department of Cardiothoracic Surgery, Oslo University Hospital, Oslo, Norway
6. Department of Biomedicine, University of Bergen, Bergen, Norway