Coronary artery ligation (CAL) was used to produce an in vivo model of cardiac arrhythmias and myocardial infarction using anaesthetized male Hooded Wistar rats which had been fed for 6-7 or 18-20 months on either a standard reference diet alone or supplemented (12% w/w) with sunflower seed oil (linoleic acid rich) or sheep kidney fat (linoleic acid poor). The number of ventricular extra beats and duration of tachycardia or fibrillation in the 30-min postligation was increased in sheep kidney fat-fed rats. Infarct size 4 h postCAL was reduced in sunflower seed oil-fed rats. Arrhythmias, infarct size, and dietary-induced differences were increased with age. The diets employed produce changes in myocardial membrane phospholipids which could result in altered prostaglandin production. These results show that in the rat (as in man), age and dietary saturated fat are risk factors for sudden cardiac death and myocardial infarction and suggest that the rat is a useful model for the investigation of dietary interventions in heart disease.

Dietary fish oil and sunflower seed oil increased the left ventricular ejection fraction in the marmoset monkey by enhancing ventricular filling, thus providing an energy sparing promotion of diastolic relaxation.

Marmoset monkeys (Callithrix jacchus) were maintained for 24 mo on a standard primate diet [reference (Ref) diet] or this diet supplemented (8% wt/wt) with either sheep fat (SF), sunflower seed oil (SSO), or tuna fish oil (TFO). The polyunsaturated fatty acids (PUFA) of myocardial phospholipids demonstrated significant alterations as a result of the dietary (n-3) or (n-6) lipid supplementation. The reduction (P less than 0.05) in prostaglandin (PG) I2 in PUFA diet-fed groups (SSO, 113.8 +/- 7.8; TFO, 87.9 +/- 8.2 compared with Ref, 153.9 +/- 7.4 pg/mg dry wt) seems to be due to the rate limitation of the endogenous substrate, because the addition of exogenous arachidonic acid (AA) has obliterated the dietary difference. However, AA did not increase the basal PGI2 production in the Ref or SF dietary groups, which differed from that for thromboxane (Tx) A2 where 2- to 5-fold stimulation was observed. It is suggested that there exists a preferential channeling mechanism to direct AA derived from phospholipase hydrolysis of membrane phospholipids toward PGI2 synthesis. Conversely, the bulk of the AA for TxA2 biosynthesis appears to be supplied by a cytosolic nonesterified fatty acid pool. The effective replacement of AA of this pool and a specific inhibition of TxA2 synthetase enzyme complex by the (n-3) PUFA of fish oil are offered as likely mechanisms for the greater inhibition of TxA2 compared with PGI2 production observed in the present and previous studies. The present data on myocardial eicosanoids correlate well with the beneficial qualities of (n-3) and (n-6) dietary PUFA on cardiac function that we have reported previously.

The effect of long-term feeding of various dietary fats and oils on cardiac arrhythmia was studied in an animal model of sudden cardiac death. After confirmation that a dietary supplement of saturated animal fat (SF) increased the animals' susceptibility to develop cardiac arrhythmia under ischemic stress whereas the polyunsaturated fatty acids of sunflower seed oil (SSO) reduced this susceptibility, we found that diets supplemented with either chemically refined palm oil (PO-I) or physically refined palm oil (PO-II) gave results that were generally intermediate in value between the SF and the SSO groups. However, during reperfusion of a previously ischemic heart, both PO-I- and PO-II-supplemented diets appeared to be as effective as SSO in reducing ventricular premature beats. In addition, the incidence of animals displaying severe ventricular fibrillation was much less after palm-oil feeding than it was after SF feeding. These preliminary results warrant further investigation of the potential antiarrhythmic effects of commercial palm oil.

The influence of dietary fat on myocardial vulnerability to arrhythmia was examined using coronary artery occlusion and reperfusion in the anesthetised rat as a whole animal model of ventricular fibrillation and sudden cardiac death. Animals were fed a reference (REF) diet alone or supplemented 12% by weight with tuna fish oil (TFO) (rich in n-3 fatty acids), sunflower seed oil (SSO) (rich in n-6 fatty acids) or sheep perirenal fat (SF) (rich in saturated fatty acids). Feeding periods of 6, 12, and 18 months and a total of 108 rats were used. The incidence of ventricular fibrillation in occlusion was reduced from 46% of REF animals to 6% and 21% in TFO and SSO groups respectively and increased to 68% in the SF-fed rats. The incidence of ventricular tachycardia was also reduced by TFO and SSO. The duration of arrhythmic episodes was increased by SF and reduced by TFO and SSO. The incidence of fibrillation on reperfusion of acutely ischemic myocardium (15 minutes occlusion) was significantly reduced by TFO only (12%, REF = 50%, SSO = 30%, SF = 70%). Severity of arrhythmias increased with age as did the extent of dietary influence. Mortality from fibrillation which only occurred in rats aged 12 months or older (REF = 13%) was increased by SF (43%) mainly in reperfusion (38%) but did not occur in TFO or SSO. These results indicate the potential benefit of dietary modification to include a higher proportion of polyunsaturated fat especially fish oil in reducing risk of sudden cardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)