DIETARY FATS AND CARDIAC-ARRHYTHMIA IN PRIMATES

Several epidemiological surveys have suggested that an alteration in t he habitual intake of the type rather than the amount of dietary fat m ay offer a nutritional means for a reduction in mortality from severe cardiac arrhythmia which cannot be achieved at present by the post hoc administration of anti-arrhythmic agents. We have examined this possi bility in a series of long term feeding studies with the small non-hum an primate marmoset monkey Callithrix jacchus. In both in vitro and in vivo studies of the mechanical performance of cardiac muscle we have found that diets rich in saturated fatty acids promote arrhythmia when the heart is subjected to pharmacological or ischemic stress. Convers ely, diets enriched in either omega-6 or omega-3 PUFA are beneficial, reducing the vulnerability to pharmacologically induced dysrhythmia in vitro or ischemic arrhythmia in vivo. In addition, PUFA enriched diet s enhance myocardial performance (left ventricular ejection fraction a nd end diastolic volume) and raise the electrical threshold at which v entricular fibrillation can be induced. These diet-induced changes in cardiac performance are accompanied by significant alterations in the PUFA composition of cardiac muscle membranes, and the subsequent produ ction of myocardial eicosanoids. Both omega-6 and omega-3 PUFA increas e the ratio of myocardial prostacyclin:thromboxane, but omega-3 PUFA i s more effective as less is required to achieve a significant decrease in pro-arrhythmic thromboxane. These results offer a nutritional basi s for the epidemiological findings of reduced mortality from sudden ca rdiac death in populations who consume less saturated fatty acids of e ither animal or plant origin, but maintain their total fat intake by s ubstitution with polyunsaturated fatty acids. Nevertheless, the greate st benefit might be expected amongst those populations having a regula r intake of the long-chain omega-3 PUFA found in many marine species, even if considerable saturated fatty acids remain in the diet.