1. Department of Pediatric Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
2. Faculty of Medicine, University of Oslo, Oslo, Norway.
3. Department of Pediatric Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
4. Department of Pediatrics, Akershus University Hospital, Norway.
5. Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
6. KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Norway.
7. Center for Heart Failure Research, Oslo University Hospital, Norway.
8. Department of Cardiothoracic Surgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway.
9. Department of Pediatrics, West Virginia University, Morgantown, VA.