Authors' objectives:

Epidemiological studies and clinical trials have reported beneficial effects of fish or fish oil consumption on cardiovascular disease outcomes including sudden death and arrhythmia. The mechanisms of this reported benefit are, however, unclear. As one component of a series of reports on the impact of omega-3 fatty acids on cardiovascular disease, we also performed a systematic review of the literature on whole animal and isolated organ and cell culture studies to assess the effects of omega-3 fatty acids on arrhythmogenic mechanisms and outcomes.

Authors' results and conclusions: Thirteen whole animal studies (rat models) were included in a meta-analysis that compared the anti-arrhythmic effects of ALA or fish oil to omega-6 oils. These meta-analysis results showed that fish oil supplementation showed a significant risk reduction in the number of deaths, ventricular tachycardia (VT), and ventricular fibrillation (VF). The combined risk ratio (RR) for deaths was 0.48 (95% CI: 0.24-0.95). With fish oil supplementation, for VT the RR was 0.49 (95%CI 0.29-0.83), and 0.68 (95%CI 0.50-0.91), for ischemia and reperfusion-induced arrhythmias, respectively. With fish oil supplementation, for VF, the RR was 0.21 (95%CI 0.07-0.63), and 0.44 (95%CI 0.25-0.79), for ischemia and reperfusion-induced arrhythmias, respectively. There was no significant effect for ALA oil supplementation, however. There were twenty-one studies using isolated organs and cells from whole animals fed omega-3 fatty acids that examined the following parameters: contractile, basoelectromechanical, ion pumps and ion movements, ion currents, and ion channels. Although seven of these studies evaluated the effect of omega-3 fatty acid enriched diets on contractile parameters, they each compared different diets and used different experimental conditions. Thirty-nine studies evaluated the effect of omega-3 fatty acids on isolated organ and cell cultures. Omega 3 fatty acids were applied either directly to the cell culture medium (free) or incubated with the cells to allow incorporation into membrane phospholipids (bound). These studies examined parameters similar to the whole animal isolated organ and cell studies. Seven studies of arrhythmia reported that omega- 3 fatty acids (predominantly EPA and DHA but in one instance ALA) appeared to have a protective effect against spontaneous or induced arrhythmias in both rat and guinea pig models. Four of these studies, however, were from the same collaborative group. In the presence of various arrhythmogenic agents and across the different types of species studied, omega-3 fatty acids compared to controls were reported to consistently decrease contraction rate, thereby exerting a protective effect with respect to arrhythmia. In studies without an arrhythmogenic agent, the results were inconsistent, with three showing a decrease in contractility and three showing no effect.

Authors' recommendations: Fish oil supplementation (EPA and/or DHA) might have anti-arrhythmic effects when compared with omega-6, monounsaturated, or saturated fatty-acids in pre-fed fish oil in studies of various animal species. Fish oil supplements in rats showed significant protective effects for ischemia- and reperfusion- induced arrhythmias by reducing the incidence of ventricular tachycardia and fibrillation but no beneficial effects for ALA supplementation were found. The arrhythmic effects for infused omega-3 fatty-acid treatments are still unknown. In studies using isolated organs and cells from animals fed omega-3 fatty acids and in studies using isolated organ and cell culture where fatty acids were directly applied to the culture medium, the question regarding plausible biochemical or physiological mechanisms to explain the potential antiarrhythmogenic effects of omega 3 fatty acids cannot be answered definitively at this time, despite some apparent trends. Due to numerous sub-parameters within each of the major electrogenesis areas (i.e. ion channels, ion currents, ion pumps and ion movement, contractility) studied , and a variety of experimental conditions, it is more difficult to draw a conclusion about the various parameters.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/tp/o3arrtp.htm

Year Published: 2004

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)