1. Clinic of Cardiology, St. Olavs Hospital, Postbox 3250 Sluppen, Trondheim, Norway
2. Department of Cardiology, Ålesund Hospital, Ålesund, Norway
3. Clinic of Thoracic Surgery, St. Olavs Hospital, Trondheim, Norway
4. Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway