All patients admitted for cardioversion for atrial fibrillation and flutter will be potentially eligible for the study. Patients will be recruited at the Regional Hospital of Randers as a part of the pre-cardioversion check. This is the first contact to patients, and they will receive oral and written information. The oral and written information will be given by a doctor and/or the primary investigator. The information will be given in a quiet setting, and the patients may ask questions about the study. It will be possible for the patient to have a companion present. Informed consent will be obtained from all participants during the pre-cardioversion check or alternatively prior to cardioversion allowing the patient to have a companion present before consent is given. Patients declining to participate in the study will receive treatment according to the standard protocol.