The RATAF II study is a randomized, prospective, parallel group study, designed to compare the effects of two different drug regimens for rate control in permanent AF (atrial fibrillation). We will investigate on the difference in effects on exercise capacity, biomarkers (NT-proBNP (N-terminal pro-brain natriuretic peptide), troponins, hs-CRP), heart rate, echocardiographic measurements and symptoms.