1. Department of Cardiology, Oslo University Hospital, Rikshospitalet, PO Box 4950 Nydalen, 0424 Oslo, Norway
2. Institute for Clinical Medicine, University of Oslo, PO Box 1171 Blindern, 0318 Oslo, Norway
3. Departement of Thoracic Surgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway
4. K. G. Jebsen Center for Cardiac Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, PO Box 1171 Blindern, 0318 Oslo, Norway