BRESCIA, ITALY. There is evidence that n-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the main components of fish oil, have antiarrhythmic effects and may help reduce sudden cardiac death. Several clinical and epidemiological studies have evaluated the effect of fish oil supplementation on the development and progression of atrial fibrillation (AF), but results have been inconclusive.

Now a team of Italian researchers reports that persistent AF patients treated with fish oil for at least 4 weeks prior to electrical cardioversion maintain normal sinus rhythm (NSR) for a considerably longer period post-conversion than do patients given placebo. Their randomized, double-blind, placebo-controlled, parallel arm clinical trial included 199 patients with persistent AF who had suffered relapse after at least one previous cardioversion. The average age of the patients was 70 years, 67% were male, 35% had diabetes, and 90% had structural heart disease, thus leaving only 10% with lone AF. All patients were on warfarin, amiodarone (200 mg/day) and an ACE inhibitor for at least 4 weeks prior to the planned cardioversion.

At the start of the study (at least 4 weeks before cardioversion), patients were randomized to a fish oil group or a control group. Members of the fish oil group received a 1-gram fish oil capsule twice daily providing a total daily intake of 920 mg of EPA and 760 mg of DHA in the form of ethyl esters (OMACOR). The control group received an identical-looking olive oil capsule twice daily. All patients underwent biphasic electrical cardioversion using an initial shock energy of 100 joule followed by a second and third 200-joule shock if the first one did not achieve NSR.

In the fish oil group, 78% of patients converted after the first shock, while only 33% in the control group did so. At the 1-year follow-up, 62% of fish oil group members were still in NSR as compared to only 36% in the placebo group. The Italian researchers conclude that fish oil supplementation for at least 4 weeks prior to electrical cardioversion markedly improves long-term maintenance of NSR in a group of persistent AF patients (90% with structural heart disease) on amiodarone and ACE inhibitor/angiotensin receptor blocker therapy.

In an accompanying editorial, Drs Camm and Savelieva of St. George's University of London emphasize that trials of fish oil supplementation have produced inconsistent results when it comes to AF. They suggest that the positive results in the Italian study may be due to the concomitant treatment with amiodarone and ACE inhibitors/angiotensin receptor blockers and/or to the fact that fish oils may be more effective in patients with extensive, long-established heart disease. They point out that "the ability of PUFAs to increase parasympathetic tone may theoretically be proarrhythmic in younger individuals with normal hearts in whom a vagal component may play a role in promoting AF. The proportion of such patients with lone AF or mild cardiovascular disease was higher in the studies that failed to demonstrate a benefit from PUFA therapy."

Nodari, S, Dei Cass, L, et al. n-3 polyunsaturated fatty acids in the prevention of atrial fibrillation recurrences after electrical cardioversion. Circulation, Vol. 124, September 6, 2011, pp. 1100-06
Camm, AJ and Savelieva, I. Fish oil for secondary prevention of atrial fibrillation – should we still believe in its antiarrhythmic effect? Circulation, Vol. 124, September 6, 2011, pp. 1093-96

Editor's comment: Although not necessarily applicable to all lone afibbers, it is possible that adrenergic and mixed persistent afibbers could benefit from fish oil supplementation (for at least 4 weeks) prior to electrocardioversion, especially if taken in combination with a suitable antiarrhythmic drug. It is interesting that no adverse events relating to fish oil supplementation were observed during the trial, thus confirming that it is safe to supplement with fish oils when on warfarin therapy.