Background: The most effective procedure to restore sinus rhythm in patients with persistent atrial fibrillation (AF) is electrical cardioversion, but AF recurs in 60-80% of the patients during the first year. AF is associated with electrical and anatomical remodelling of the atria, and angiotensin II is involved in the remodelling process. Studies have indicated that the angiotensin II type 1 receptor antagonist candesartan may counteract both electrical and anatomical remodelling induced by AF. The investigators therefore hypothesised that treatment with candesartan may reduce the recurrence rate of AF after electrical cardioversion.