Unlike for ventricular arrhythmias, the role of n-3 PUFAs in atrial arrhythmias has not been fully investigated. A recently published epidemiological study reported that in elderly patients, consumption of fish was associated with a lower incidence of atrial fibrillation over the 12 years of follow-up. This observation may be an indirect effect due to the overall beneficial effort of fish consumption on reducing ischaemic heart disease, however this association persisted after adjustment for confounding characteristics. Clinical data regarding the direct impact of n-3 PUFAs on atrial arrhythmias such as atrial fibrillation/flutter (AF) is lacking. However, as both INa and ICa-L are also in atrial myocytes, similar anti-fibrillatory actions by n-3PUFAs would be expected in atrial fibrillation and we would like to investigate this further. The primary aim of this study is to investigate whether dietary supplements of n-3 PUFA concentrates (1g fish oil/day comprising eicosapentaenoic acid, EPA 46% and docosahexaenoic, DHA 38%)) helps maintain sinus rhythm after cardioversion to normal sinus rhythm in patients with persistent atrial fibrillation.