Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. AF treatment involves management of precipitating factors, rate- and rhythm control and anticoagulation for prevention of stroke and systemic thromboembolism. The aims of this thesis were to describe clinical practice in prescription of anticoagulation therapy and trends in ischemic stroke incidence among AF patients, to report plasma concentrations of anticoagulant dabigatran at 110 mg bid under concomitant treatment with antiarrhythmic agent dronedarone in real-life patients and to assess ECG-derived indices of AF organization as predictors of cardioversion with vernakalant. A considerable proportion of AF patients do not receive adequate stroke prevention therapy with oral anticoagulation, despite increased guideline adherence. Efforts to reduce under-treatment should particularly be targeted on female patients < 65 years with additional stroke risk factors and elderly > 84 years. The increased use of oral anticoagulants between 2011 and 2013 in patients with incident AF is associated with decline in the cumulative incidence of ischemic stroke in Skåne County. Dronedarone and dabigatran are often indicated in the same patient population. Trough plasma concentration of dabigatran at 110 mg bid dose with dronedarone was comparable to plasma dabigatran concentration at the dose of 150 mg bid without concomitant dronedarone in RE-LY study with reportedly low rates of major bleeding and thrombosis. Larger trials on efficacy and safety of this treatment strategy might refute the present contraindication. ECG-derived markers of atrial remodelling failed to predict treatment response in acute cardioversion of AF with vernakalant.