Absence of coronary or aortic atherosclerosis in rats having dietary lipid modified vulnerability to cardiac arrhythmias.

Laboratory studies have shown that saturated fats in the diet increase vulnerability to ventricular fibrillation and other cardiac arrhythmias while polyunsaturates, especially the n-3 fatty acids of fish oils, are antiarrhythmic. Similarly, dietary saturated fat has been implicated in the development of coronary atherosclerosis while polyunsaturated fatty acids are reported to provide protection. In the present study, dietary fat supplements known to influence arrhythmic vulnerability after long term feeding in the rat were tested for their propensity to induce or prevent changes in the aorta or coronary vasculature. It was found that dietary supplementation for 15 months with saturated fat (from sheep fat) or n-6 (sunflower seed oil) or n-3 (fish oil) polyunsaturated fatty acids made no difference to the development of vascular changes in coronary arteries or aorta of the rat despite some significant differences in plasma triglyceride and cholesterol levels. The vascular lesions observed were minimal even in non-supplemented age-matched reference animals. They consisted of focal intimal thickening and slight mucopolysaccharide accumulation with no evidence of progression to fibrotic lesions or calcium accumulation and there were no fatty deposits observed. It is concluded that significant atherosclerosis-induced chronic myocardial ischaemia in no way contributes to dietary lipid modulation of arrhythmic vulnerability in the rat.