PREVENTION OF ISCHEMIA-INDUCED VENTRICULAR-FIBRILLATION BY OMEGA-3-FATTY-ACIDS

A specially prepared dog model of myocardial infarction was used to te st the efficacy of the long-chain polyunsaturated fish oil omega 3 fat ty acids eicosapentaenoic (20:5 n-3) and docosahexaenoic (22:6 n-3) ac ids to prevent ischemia-induced malignant cardiac arrhythmias. The dog s had sustained a prior experimental myocardial infarction from ligati on of the left anterior descending coronary artery, and a hydraulic cu ff was implanted around the left circumflex artery at that operation. After recovery from that procedure the animals were tested during a tr eadmill exercise test. With compression of the left circumflex artery sensitive animals will predictably develop ventricular fibrillation (V F). In such prepared dogs an emulsion of fish oil fatty acids was infu sed i.v. over a 50- to 60-min period just before the exercise-plus-isc hemia test, and the effect on development of VF was recorded. The infu sion was 100 ml of a 10% (vol/vol) emulsion of a fish oil concentrate containing 70% omega 3 fatty acids with free eicosapentaenoic acid and docosahexaenoic acid composing 33.9% and 25.0% of that total, respect ively. Alternatively, some animals similarly received an emulsion cont aining 5 ml of the free fatty acid concentrate plus 5 ml of a triacylg lyerol concentrate containing 65% omega 3 fatty acids with eicosapenta enoic acid and docosahexaenoic acid composing 34.0% and 23.6% of that total, respectively. In seven of eight animals the infusion of the fis h oil emulsion completely prevented the acute occurrence of VF in the susceptible animals (P < 0.005). In five of five of these animals the subsequent exercise-plus ischemia test after a similar infusion of an emulsion in which soy bean oil replaced the fish oil fatty acid concen trates resulted in prompt development of VF. Possible mechanisms for t his protective effect of omega 3 fatty acids against exercise and isch emia-induced malignant arrhythmias are considered.