Lenient Rate Control Versus Strict Rate Control for Atrial Fibrillation. The Danish Atrial Fibrillation Randomised Clinical Trial

Inclusion Criteria: 1. Participants with atrial fibrillation (ECG confirmed and diagnosed by the treatment provider) who at inclusion have either persistent (defined as atrial fibrillation for more than 7days) or permanent atrial fibrillation (only rate control is considered going forward). 2. Rate control must be accepted as being the primary management strategy going forward. Consideration towards whether rhythm control is more appropriate must be considered, especially given the results of the Early treatment of Atrial fibrillation for Stroke prevention Trial (EAST). 3. Informed consent. 4. Adult (18 years or older). Exclusion Criteria: 1. No informed consent. 2. Initial heart rate under 80 bpm at rest (assessed via ECG before randomisation). 3. Less than 3 weeks of anticoagulation with new oral anticoagulants or 4 weeks with efficient warfarin if indicated. 4. If the treating physician deems that the participant is not fit to be randomised into both groups based on an individual assessment. Such a decision will be made before randomisation by the treating physician. This can e.g. be participants dependent on a high ventricular rate to maintain a sufficient cardiac output. Such participants could be participants with heart failure, participants with a hemodynamically significant valve dysfunction, or severely dehydrated participants. 5. Participants who are haemodynamically unstable and therefore require immediate electrical cardioversion