PATIENTS WITH ATRIAL FIBRILLATION Patients presenting with ECG-documented atrial fibrillation are included if unstable, i.e. if heart rate exceeds 100 and in-patient treatment is indicated. Patients are excluded if they suffer from unstable ischaemic heart disease (unstable angina or myocardial infarction), heart failure with LVEF ≤ 40% or if the arrhythmia is secondary to another condition such as an infection.