1. Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim and Faculty of Medicine, Medical Technology Center, Olav Kyrres gt. 3, 7489 Trondheim, Norway
2. Department of Cardiology and Lung Medicine, St Olavs Hospital HF, Trondheim, Norway
3. Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA