1. Dept. of Cardiology, Oslo University Hospital Ullevaal , Kirkeveien 166, 0450 Oslo , Norway
2. Institute of Clinical Medicine, University of Oslo , Kirkeveien 166, Soesterhjemmet, 0450 Oslo , Norway
3. Division of Cardiology, Clinical Electrophysiology Unit, Instituto Cardiocentro Ticino , Lugano , Switzerland
4. Department of Medical Science, Uppsala University , Uppsala , Sweden
5. Department of Cardiology, School of Medical Sciences, Faculty of Medicine and Health, Örebro University , Örebro , Sweden