1 University of Oslo, Medical Faculty, Institute for Clinical Medicine, Oslo, Norway; Oslo University Hospital Ullevaal, Departments of Cardiology and Nephrology, Oslo, Norway. Electronic address: s.e.kjeldsen@medisin.uio.no.
2 Department of Internal Medicine, Lovisenberg Hospital, Oslo, Norway.
3 University of Oslo, Medical Faculty, Institute for Clinical Medicine, Oslo, Norway; Oslo University Hospital Ullevaal, Departments of Cardiology and Nephrology, Oslo, Norway.