Dietary fish oil and ischaemic arrhythmias

Ventricular fibrillation (VF), a serious arrhythmia, is an important cause of death from ischaemic heart disease. There is substantial evidence that experimental diets with a high polyunsaturated (linoleic acid) to saturated fatty acid ratio offer protection against VF. In this article the effects of large amounts of dietary fish oil (up to 30% cal) are reviewed. It is concluded that in all recently published studies marked increases in the incorporation of n-3 fatty acids in membranes was achieved. Two studies were too small, however, to demonstrate any statistically significant difference in VF. The results from a third, a long term feeding study, show a reduction in VF when compared with a highly saturated fat diet, but not when compared to a polyunsaturated fatty acid (n-6) rich diet. Using a more realistic fish oil supplement (0.4% cal) for 8 weeks, we observed a small but nonsignificant reduction in the incidence of VF during acute myocardial ischaemia in the isolated perfused rat heart. The need for further work on the effect of dose, dietary period and confounding influences of saturated fatty acids and linoleic acid are discussed.