1. Karolinska Institutet, Department of Clinical Sciences, Unit of Cardiology, Danderyd University Hospital, Stockholm, Sweden
2. Department of Clinical Physiology, Capio S:t Görans Hospital, Stockholm, Sweden
3. Department of medical engineering, KTH Royal Institute of Technology, Stockholm, Sweden
4. Karolinska Institutet, Department of Clinical Science, Section of cardiology, South Hospital, Stockholm, Sweden