Omega-3 fatty acids: antiarrhythmic, proarrhythmic or both?

PURPOSE OF REVIEW: Recent publications seem to indicate no or an untoward effect of the marine omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid on cardiac rhythm. This review puts these developments into perspective. RECENT FINDINGS: In-vitro or in animal models, little pro-arrhythmic effect, but many antiarrhythmic mechanisms of omega-3 fatty acids have been documented. In intervention studies in humans, eicosapentaenoic acid plus docosahexaenoic acid suppressed new atrial fibrillation in patients undergoing coronary bypass grafting. More importantly, in systematic reviews, it has been demonstrated that eicosapentaenoic acid plus docosahexaenoic acid reduce sudden cardiac death by 50%. In a recently published intervention study with eicosapentaenoic acid in patients at high cardiovascular risk in Japan, sudden cardiac death was rare. Sudden cardiac death is even rarer in the general population of Japan: it occurs 20 times less frequently than in the general population in Europe, e.g. Germany. In Japan, levels of eicosapentaenoic acid plus docosahexaenoic acid are high (omega-3 index estimated around 11%), whereas in Germany levels of eicosapentaenoic acid plus docosahexaenoic acid acids are low (omega-3 index around 4%). These and other data strengthen the concept that a low omega-3 index is a risk factor for sudden cardiac death, as a tool to assess the status of a person in terms of eicosapentaenoic acid plus docosahexaenoic acid, and as a means to monitor therapy with eicosapentaenoic acid plus docosahexaenoic acid. SUMMARY: Concerns about pro-arrhythmic effects of eicosapentaenoic acid plus docosahexaenoic acid are largely theoretical. The evidence in favour of an antiarrhythmic effect is overwhelming, especially, when factoring in the omega-3 index.