Background—Rat diets high in fish oil have been shown to be protective against ischemia-induced fatal ventricular arrhythmias. Increasing evidence suggests that this may also apply to humans. To confirm the evidence in animals, we tested a concentrate of the free fish-oil fatty acids and found them to be antiarrhythmic. In this study, we tested the pure free fatty acids of the 2 major dietary ω-3 polyunsaturated fatty acids in fish oil: cis-5,8,11,14,17-eicosapentaenoic acid (C20:5ω-3) and cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6ω-3), and the parent ω-3 fatty acid in some vegetable oils, cis-9,12,15-α-linolenic acid (C18:3ω-3), administered intravenously on albumin or a phospholipid emulsion.

Methods and Results—The tests were performed in a dog model of cardiac sudden death. Dogs were prepared with a large anterior wall myocardial infarction produced surgically and an inflatable cuff placed around the left circumflex coronary artery. With the dogs running on a treadmill 1 month after the surgery, occlusion of the left circumflex artery regularly produced ventricular fibrillation in the control tests done 1 week before and after the test, with the ω-3 fatty acids administered intravenously as their pure free fatty acid. With infusion of the eicosapentaenoic acid, 5 of 7 dogs were protected from fatal ventricular arrhythmias (P<0.02). With docosahexaenoic acid, 6 of 8 dogs were protected, and with α-linolenic acid, 6 of 8 dogs were also protected (P<0.004 for each). The before and after control studies performed on the same animal all resulted in fatal ventricular arrhythmias, from which they were defibrillated.

Conclusions—These results indicate that purified ω-3 fatty acids can prevent ischemia-induced ventricular fibrillation in this dog model of sudden cardiac death.