A comparison of methods used to calculate ultrasonic myocardial backscatter in the time domain

The cyclic variation of ultrasonic integrated backscatter from the left ventricular posterior wall and interventricular septum of the heart is now well documented in the literature, with minimal values occurring at end-systole and maximal at end-diastole. However, little work has been performed to date to determine whether cyclic cardiac variation of other, more easily derived, backscatter parameters exists. In this study, 20 baseline, epicardial, long-axis cardiac-cycle sequences were obtained from eight open-chest pigs, yielding a total of 285 ultrasonic frames of RF data, which were analysed off-line on a Sun workstation. In addition, the video data from these studies was digitised and collected from each scan. Five backscatter parameters, calculated in the time-domain, including (1) the average integrated backscatter; (2) the average of the backscatter power from the log-compressed data; (3) the square of the average of the uncompressed radio frequency (RF) amplitude; (4) the square of the average of the RF amplitude from the log-compressed data; and (5) the square of the average grey-scale video data, were analysed and their variation throughout the cardiac cycle correlated against that obtained from integrated backscatter measurements. The backscatter values obtained were referenced to a gel calibration phantom widely used for 2-D calibration studies. Significant (p < 0.001), good correlation existed between the four backscatter parameters derived from the RF data. Reduced correlation was obtained between the video backscatter parameter and those derived from the RF data. Maximum cyclic variation between systole and diastole was measured from the integrated backscatter parameter and minimum from the three log-compressed data sets.

Effect of dietary polyunsaturated fatty acids on contraction and relaxation of rat femoral resistance arteries

We investigated the effects of dietary polyunsaturated fatty acids (PUFA) derived from fish oil (n-3 PUFA) and plant seed oil (n-6 PUFA), in amounts relevant to human consumption, on the alpha 1-adrenoceptor-mediated contractile responses of isolated rat resistance arteries. Rats were fed semisynthetic diets, deriving 40% of total calories from fat. The control diet, which had sufficient linoleic acid to prevent essential fatty acid deficiency, had a polyunsaturated/saturated fatty acid (P/S) ratio of 0.3. The n-3 PUFA were given as a daily oral supplement of fish oil. For the n-6 PUFA diet, the proportion of linoleic acid in the diet was increased to obtain P/S ratio of 2.0. Diets were administered for 8 weeks. At the end of the feeding period, second-order branches of the femoral artery (< 300-micros diameter) were mounted in pairs in an isometric myograph, and responses to norepinephrine (NE) 3 nM-10 microM with addition of yohimbine 1 microM and timolol 1 microM were examined. Subsequently, the vessels were preconstricted with NE to 60% of their maximal response and relaxation to acetylcholine 1 nM-0.1 mM was observed. Dietary n-3 PUFA supplements led to attenuation of the contractile responses of isolated resistance arteries (p < 0.01, repeated-measures analysis of variance, ANOVA-RM) versus control. The n-6 PUFA diet did not exert this effect although there was a downward trend. Diet did not affect EC50 values for NE. Neither n-3 nor n-6 PUFA diet influenced relaxation responses. The fatty acid composition of myocardial phospholipid fractions was significantly altered by both diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Linoleic acid and risk of sudden cardiac death

OBJECTIVE

To test the hypothesis that the essential fatty acid, linoleic acid, measured in adipose tissue as an indicator of long term dietary intake, is inversely related to the risk of sudden cardiac death.

DESIGN

A population case-control study.

SETTING

A regional health district.

SUBJECTS

84 men (age 25-64 years) who died instantaneously or within 24 hours of the onset of symptoms with no history of coronary heart disease or medically treated hyperlipidaemia, and in whom coronary artery disease was diagnosed at postmortem examination as the primary cause of death, were compared with 292 age (to within two years) and sex matched healthy controls and their partners drawn from the general practitioners' records with whom the cases were registered.

MAIN OUTCOME MEASURES

Fatty acid composition of adipose tissue and the risk of sudden cardiac death.

RESULTS

Linoleic acid in adipose tissue was inversely related to the risk of sudden cardiac death. The estimated relative risk (95% CI) of sudden cardiac death was 5.7 (1.8 to 17.9) for the lowest quintile and 4.0 (1.2 to 12.9) for the next quintile of adipose linoleic acid in the control population when compared with the highest quintile. This inverse relation was independent of age, reported smoking habits, history of hypertension, and diabetes, although there was a close association with cigarette smoking. The estimated adjusted proportionate increase in risk (95% CI) of sudden cardiac death was 1.14 (1.03 to 1.23) for every 1% reduction of linoleic acid in adipose tissue.

CONCLUSIONS

The percentage content of linoleic acid in adipose tissue was inversely related to the risk of sudden cardiac death. Populations with a high risk of sudden cardiac death may benefit from increasing their dietary intake of polyunsaturated fatty acid oils, principally from cereals and vegetables.

Propranolol and lidocaine inhibit neural norepinephrine release in hearts with increased extracellular potassium and ischemia

BACKGROUND

Propranolol and lidocaine are effective antiarrhythmic drugs in myocardial ischemia and infarction. As sympathetic nerve activation and norepinephrine release in ischemic hearts are arrhythmogenic, we tested the possibility that both agents inhibit neural norepinephrine release following sympathetic activation in the ischemic environment.

METHODS AND RESULTS

The model used was an in situ perfused innervated rat heart. Norepinephrine release was induced by electrical stimulation of the left cervicothoracic stellate ganglion and analyzed using radioenzymatic assay or high-performance liquid chromatography. In normoxically perfused hearts, evoked norepinephrine release was not affected by either of the two agents at doses of 1 to 10 mumol/L when extracellular K+ concentration was 4 mmol/L but dose-dependently reduced at 10 mmol/L K+ (D,L-propranolol: -53 +/- 4% at 1 mumol/L and -64 +/- 6% at 10 mumol/L K+, lidocaine: -37 +/- 11% at 0.1 mumol/L, -67 +/- 5% at 1 mumol/L, and -75 +/- 6% at 10 mumol/L). At 10 mmol/L K+, norepinephrine release was not affected by timolol or atenolol (both 10 mumol/L but was equally inhibited by D- or L-propranolol at 10 mumol/L (-56 +/- 5% and -53 +/- 9%, respectively), indicating a beta-blocking-independent mechanism. In hearts with metabolic acidosis (pH 6.85) at K+ of 4 mmol/L, neural norepinephrine release was also reduced by propranolol at 10 mumol/L (-37%). Finally, in hearts perfused with 4 mmol/L K+ and subjected to 6-minute periods of ischemia, neural norepinephrine release was similarly suppressed by D,L-propranolol (-38 +/- 6% at 0.1 mumol/L, -44 +/- 5% at 1 mumol/L, and -78 +/- 3% at 10 mumol/L) or lidocaine (-39 +/- 7% at 0.1 mumol/L, -58 +/- 9% at 1 mumol/L, and -91 +/- 3% at 10 mumol/L).

CONCLUSIONS

These data indicate that propranolol and lidocaine inhibit neural norepinephrine release via a Na+ channel-blocking mechanism that is synergistic with changes induced by ischemia, primarily raised extracellular K+. This mechanism may contribute to the anti-ischemic and antiarrhythmic properties of both agents in acute myocardial ischemia, which induces increased extracellular K+ and sympathetic activation.

Lack of modulation by dietary unsaturated fats on sympathetic neurotransmission in rat hearts

We examined the effect of dietary polyunsaturated fatty acids (PUFA) on cardiac sympathetic neurotransmission. Rats were fed semisynthetic diets (18.5% fat wt/wt) high in saturated fatty acids (control diet), high in n-6 PUFA (corn oil), or enriched with n-3 PUFA (Maxepa). A perfused innervated heart model was used to examine different aspects of sympathetic neurotransmission 10 wk after the feeding. Dietary PUFA increased the content of n-6 or n-3 PUFA in myocardial phospholipids compared with animals fed control diets. Myocardial norepinephrine content, sympathetic nerve stimulation-induced norepinephrine release, neural reuptake, presynaptic alpha-adrenergic inhibition of norepinephrine release, and postsynaptic inotropic response (+/- dP/dt) to sympathetic nerve stimulation or to a beta-agonist were essentially not influenced by dietary PUFA. Neural norepinephrine release during prolonged ischemia (60 min) was also similar in hearts from rats fed n-6 PUFA and control diets. Thus a modification of sympathetic neurotransmission was not achieved by feeding PUFA-enriched diets for 10 wk.

Sympathetic activation and increased extracellular potassium: synergistic effects on cardiac potassium uptake and arrhythmias

During acute myocardial ischemia, a combination of increased extracellular K+ concentration and sympathetic nerve activation exists. Using a perfused innervated rat heart model, we studied the influence of increased extracellular K+ concentrations on neural norepinephrine (NE) release, adrenergic stimulation-induced K+ uptake by the heart, and the occurrence of ventricular arrhythmias. Hearts were globally perfused with control (4 mM) or increased concentrations of K+ (7-16 mM). Sympathetic nerve stimulation-induced NE release was analyzed by radioenzymatic assay. Cardiac K+ uptake was assessed by the reduction in K+ concentration in the coronary venous effluent induced by nerve stimulation. Neural NE release was not influenced by increasing K+ from 4 mM to 7, 10, and 13 mM, but was suppressed by 16 mM K+ (-40 +/- 10%). Nerve stimulation induced cardiac uptake of K+, which was blocked by the beta-adrenoceptor antagonist timolol. This stimulated K+ uptake was substantially enhanced by increasing extracellular K+ and was also dependent on the intensity of sympathetic stimulation at 10 mM K+. Sympathetic nerve stimulation, together with a high K+ of 10 mM, was potent in initiating ventricular tachyarrhythmias, and quantitative NE release was well correlated with the frequency of ventricular arrhythmias. Our results demonstrate the synergistic effects of increased extracellular K+ and sympathetic activation, which may be involved in the genesis of ventricular arrhythmias.

Serum cholesterol, triglycerides, and aggression in the general population

A higher than expected number of violent deaths and suicides in coronary prevention trials has provoked interest in the possibility that low serum cholesterol concentrations are associated in the general population with personality characteristics predisposing to aggressive and suicidal behaviour. We have investigated this possibility in the Edinburgh Artery Study. We measured serum lipid concentrations in blood samples taken from fasting subjects and assessed personality characteristics on the Bedford Foulds Personality Deviance Scales in a random sample of 1592 men and women aged 55-74 years, selected from age-sex registers of ten general practices in Edinburgh. Serum cholesterol concentration was not significantly associated with aggression in men, but it was associated in multivariate analysis (though not univariate analysis) with denigratory attitudes towards others among women. However, serum triglyceride concentration was related, especially in men, to hostile acts (r = 0.13, p < 0.001) and domineering attitude (r = 0.12, p < 0.001) independently of age, total and HDL cholesterol, cigarette smoking, and alcohol consumption. Subjects taking part in prevention trials have higher triglyceride concentrations than the general population and the relation between serum triglyceride concentration and aggression merits further investigation.

Glucose tolerance, plasma insulin, HDL cholesterol and obesity: 12-year follow-up and development of coronary heart disease in Edinburgh men

The insulin response to a standard oral glucose tolerance test (OGTT) and other anthropometric and biochemical risk factors for coronary heart disease (CHD) were measured in a random sample of 107 Edinburgh men, who were initially studied in 1976 when they were 40 and who were reexamined in 1988-89. Fasting glucose and glucose response to OGTT were higher in 1988-89 than in 1976. In contrast, insulin levels did not differ between the initial and follow-up study either before or after the glucose load. Body mass indices increased, except triceps skinfold. Changing patterns in both fasting and OGTT insulin or glucose levels in individuals were related to changes in bodyweight or in subscapular skinfolds. Modifications in serum total and HDL cholesterol were related to changes in fasting insulin and insulin area, respectively, but not to glucose data. Eleven men developed clinical CHD. Neither glucose nor insulin measures obtained in 1976 differed between those with and without CHD. Weight-height index and abdominal skin-folds were higher in those with CHD. HDL cholesterol was significantly lower (P less than 0.05). Abdominal skin-fold but not body mass index remained significant when adjusted for HDL cholesterol. This small study confirms the importance of central obesity and low HDL cholesterol but failed to identify insulin as a risk factor for CHD in this Scottish population.

Smoking, lipids, glucose intolerance, and blood pressure as risk factors for peripheral atherosclerosis compared with ischemic heart disease in the Edinburgh Artery Study

The aim was to determine if certain risk factors in the general population are more strongly related to peripheral arterial disease than to ischemic heart disease. Arterial disease in the lower limbs was measured by means of the World Health Organization questionnaire on intermittent claudication, the ankle brachial pressure index, and a reactive hyperemia test in 1,592 men and women aged 55-74 years selected randomly in 1988 from the age-sex registers of 10 general practices in Edinburgh, Scotland. Peripheral arterial disease was strongly related to lifetime cigarette smoking, with additional risks in current and exsmokers of less than 5 years. Multiple regression of risk factors on measures of peripheral arterial disease showed associations with diabetes mellitus (but not impaired glucose tolerance), systolic blood pressure, and serum cholesterol; inverse association with high-density lipoprotein cholesterol; and only univariate association with triglycerides. In multiple logistic regressions of risk factors on six separate indicators of cardiovascular disease, the only consistent difference was that smoking increased the risk of peripheral arterial disease (range of odds ratios, 1.8-5.6) more than heart disease (range of odds ratios, 1.1-1.6). Diabetes mellitus was not a stronger risk factor for peripheral arterial disease.

Effects of presynaptic α-adrenoceptors and neuronal reuptake on noradrenaline overflow and cardiac response

Using an in situ perfused, innervated rat heart model, we studied the effects of presynaptic alpha-adrenergic and neuronal reuptake inhibition on evoked noradrenaline (NA) overflow and the postsynaptic response by sympathetic ganglion stimulation. NA overflow was significantly increased by neuronal reuptake inhibitors (desipramine and (+)-oxaprotiline) or by alpha-adrenoceptor antagonists (phentolamine and yohimbine), but the inotropic response was augmented only by alpha-antagonists. In the presence of desipramine, nerve stimulation induced a frequency-dependent increase in NA overflow and postsynaptic response, both were enhanced by yohimbine. In the absence of desipramine, however, postsynaptic response was potentiated by yohimbine despite an unchanged (at 2 and 5 Hz) or even reduced NA overflow (at 10 Hz). Thus, this study suggests that NA release and cardiac response are modulated by presynaptic alpha-adrenoceptors, and that the neuronal reuptake modifies the amount of NA overflow but has little effect on the postsynaptic response.

Total cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol and coronary heart disease in Scotland

OBJECTIVE

To investigate long term changes in total cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol concentrations and in measures of other risk factors for coronary heart disease and to assess their importance for the development of coronary heart disease in Scottish men.

DESIGN

Longitudinal study entailing follow up in 1988-9 of men investigated during a study in 1976.

SETTING

Edinburgh, Scotland.

SUBJECTS

107 men from Edinburgh who had taken part in a comparative study of risk factors for heart disease with Swedish men in 1976 when aged 40.

INTERVENTION

The men were invited to attend a follow up clinic in 1988-9 for measurement of cholesterol concentrations and other risk factor measurements. Eighty three attended and 24 refused to or could not attend.

MAIN OUTCOME MEASURES

Changes in total cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol concentrations, body weight, weight to height index, prevalence of smoking, and alcohol intake; number of coronary artery disease events.

RESULTS

Mean serum total cholesterol concentration increased over the 12 years mainly due to an increase in the low density lipoprotein cholesterol fraction (from 3.53 (SD 0.09) to 4.56 (0.11) mmol/l) despite a reduction in high density lipoprotein cholesterol concentration. Body weight and weight to height index increased. Fewer men smoked more than 15 cigarettes/day in 1988-9 than in 1976. Blood pressure remained stable and fasting triglyceride concentrations did not change. The frequency of corneal arcus doubled. Alcohol consumption decreased significantly. Eleven men developed clinical coronary heart disease. High low density lipoprotein and low high density lipoprotein cholesterol concentrations in 1976, but not total cholesterol concentration, significantly predicted coronary heart disease (p = 0.05). Almost all of the men who developed coronary heart disease were smokers (91% v 53%, p less than 0.05).

CONCLUSION

Over 12 years the lipid profile deteriorated significantly in this healthy cohort of young men. Smoking, a low high density lipoprotein concentration and a raised low density lipoprotein concentration were all associated with coronary heart disease in middle aged Scottish men, whereas there was no association for total cholesterol concentration. The findings have implications for screening programmes.

Relationships of plasma viscosity, coagulation and fibrinolysis to coronary risk factors and angina

Plasma viscosity, molecular markers of activated coagulation and fibrinolysis (fibrinopeptides A and B beta 15-42), coagulation factors (fibrinogen and factor VII) and antiplasmins were measured in 529 men aged 35-54 years and related to new angina pectoris (n = 117) and to coronary risk factors in controls without angina (n = 412). Five major risk factors (cigarette-smoking, blood pressure, cholesterol, triglyceride and body mass index) were each associated with increases in plasma viscosity, coagulation factors, and imbalance of coagulation over fibrinolysis (increased ratio of fibrinopeptide A/fibrinopeptide B beta 15-42). Increased viscosity and fibrinogen in smokers were partly reversed in ex-smokers, but the imbalance of coagulation and fibrinolysis persisted. Cholesterol and triglyceride were also associated with increased antiplasmin activity. In men with angina, only fibrinogen was elevated compared to controls. We suggest that increased plasma viscosity and an imbalance of coagulation over fibrinolysis may be mechanisms by which known risk factors promote arterial thrombosis, but are not present in stable angina.

Sex difference in presynaptic adrenergic inhibition of norepinephrine release during normoxia and ischemia in the rat heart

Using a perfused innervated rat heart model, we studied the sex difference in the sympathetic nerve stimulation-induced norepinephrine release and its presynaptic alpha 2-adrenergic inhibition in normoxic and ischemic conditions. During normoxic perfusion, the alpha 2-adrenoceptor antagonist rauwolscine resulted in a higher overflow of norepinephrine during nerve stimulation in females than in males (p less than 0.05). This more marked potentiation of norepinephrine overflow in females was accompanied by an increased chronotropic and inotropic response (p less than 0.01). During early stop-flow ischemia neural norepinephrine overflow was lower in female than in male hearts (p less than 0.005). Rauwolscine enhanced norepinephrine overflow more in females than in males (p less than 0.05), thereby eliminating the initial difference in norepinephrine overflow during ischemia between the two sexes. Ovariectomy attenuated the presynaptic alpha 2-adrenergic inhibition of norepinephrine release compared with sham-operated females (p less than 0.02). No sex difference was found in either cardiac norepinephrine content or nonexocytotic norepinephrine overflow induced by a 40-minute period of stop-flow ischemia. Thus, presynaptic alpha 2-adrenergic inhibition of myocardial norepinephrine release is greater in female than in male rats. This difference persists into the early phase of ischemia and is largely responsible for the lower neural norepinephrine release in the female heart. Female hormones may increase presynaptic alpha 2-adrenergic activity in the heart.

Risk of angina pectoris and plasma concentrations of vitamins A, C, and E and carotene

The relation between risk of angina pectoris and plasma concentrations of vitamins A, C, and E and carotene was examined in a population case-control study of 110 cases of angina, identified by the Chest Pain Questionnaire, and 394 controls selected from a sample of 6000 men aged 35-54. Plasma concentrations of vitamins C and E and carotene were significantly inversely related to the risk of angina. There was no significant relation with vitamin A. Smoking was a confounding factor. The inverse relation between angina and low plasma carotene disappeared and that with plasma vitamin C was substantially reduced after adjustment for smoking. Vitamin E remained independently and inversely related to the risk of angina after adjustment for age, smoking habit, blood pressure, lipids, and relative weight. The adjusted odds ratio for angina between the lowest and highest quintiles of vitamin E concentrations was 2.68 (95% confidence interval 1.07-6.70; p = 0.02). These findings suggest that some populations with a high incidence of coronary heart disease may benefit from eating diets rich in natural antioxidants, particularly vitamin E.

Noradrenaline release from the rat heart during anoxia: effects of changes in extracellular sodium concentration and inhibition of sodium uptake mechanisms

1. Anoxic perfusion of the isolated rat heart releases noradrenaline in the absence of sympathetic nerve fibre stimulation. 2. Anoxic noradrenaline release is enhanced by reducing the extracellular Na+ concentration, consistent with the proposal that such release occurs by carrier-mediated efflux. 3. Release is also enhanced by lignocaine but inhibited by amiloride and ethylisopropylamiloride, suggesting that sodium entry into adrenergic nerve terminals during anoxia occurs by Na+/H+ (and possibly Na+/Ca2+) exchange.

Reduced neuronal noradrenaline overflow in the ischaemic rat heart: importance of the severity of coronary flow reduction

The effects of severity and duration of acute myocardial ischaemia on left stellate ganglion stimulation-induced noradrenaline (NA) overflow were studied in the retrogradely perfused, innervated rat heart. A 10-min period of ischaemia induced by a coronary flow reduction of 100% (0 ml/g/min), 95% (0.24 ml/g/min) and 90% (0.48 ml/g/min) reduced neuronal NA overflow to 24 +/- 4% (p less than 0.01), 62 +/- 6% (p less than 0.05) and 70 +/- 6% (p less than 0.05) of the normoxic control values, respectively. During low-flow ischaemia, a progressive decline in neuronal NA overflow was found in hearts subjected to 95% flow reduction, but not to 90% flow reduction. The effect of ischaemia on presynaptic control of NA release was also examined. After 10 min of stop-flow ischaemia, the alpha-adrenergic antagonist phentolamine (1 microM) and the adenosine receptor antagonist 8-phenyltheophylline (10 microM) failed to restore neuronal NA overflow to pre-ischaemic levels (from 24 +/- 4% without drug to 23 +/- 4% or 41 +/- 10%, respectively, NS). In contrast, after 60 min of low-flow ischaemia (95% flow reduction), phentolamine and 8-phenyltheophylline largely restored neuronal NA overflow to normoxic control values (from 32 +/- 3% without drug to 61 +/- 11% (p less than 0.05) or 79 +/- 11% (p less than 0.01), respectively). During prolonged low-flow ischaemia (95%), the neuronal NA reuptake inhibitor desipramine (0.1 microM) doubled NA overflow induced by nerve stimulation, suggesting an effective neuronal reuptake during these conditions. In conclusion, the severity of ischaemia critically affects neuronal NA release and its controlling mechanisms. Thus, heterogeneity of myocardial ischaemia may lead to gradients in NA release and myocardial adrenergic stimulation.

Failure of the cholinergic modulation of norepinephrine release during acute myocardial ischemia in the rat

The effect of ischemia on cholinergic presynaptic inhibition of exocytotic norepinephrine release was studied in the innervated perfused rat heart. In normoxic hearts, vagal nerve stimulation significantly reduced exocytotic norepinephrine overflow to 75% of control values. This inhibitory effect was not affected by 3 minutes of low-flow ischemia (67% of control overflow values), but was attenuated or abolished by 10-minute low-flow ischemia or by 1-, 3-, and 5-minute stop-flow ischemia (107%, 85%, 101%, and 120% of control overflow values, respectively). The alpha-adrenergic antagonist phentolamine could completely or partly restore the failure of vagally induced inhibition of norepinephrine overflow in hearts with 1-, 3-, and 5-minute stop-flow ischemia (72%, 73%, and 85% of control overflow values, respectively). The muscarinic agonist methacholine substantially inhibited norepinephrine overflow to 18% of control overflow values in normoxic hearts. This effect was also significantly attenuated by 10-minute low-flow ischemia or by 1-, 3-, and 5-minute stop-flow ischemia (46%, 38%, 53%, and 55% of control overflow values, respectively). The cholinesterase inhibitor physostigmine did not restore the methacholine-induced inhibition of norepinephrine overflow after 3-minute stop-flow ischemia to normoxic level (55% vs. 17%). These results indicate that myocardial ischemia interferes with endogenous and exogenous cholinergic presynaptic inhibition of norepinephrine overflow in the rat heart. The extent of this attenuation depends on the severity and duration of ischemia. Reduced exocytotic acetylcholine release, which is at least in part due to an enhanced adrenergic presynaptic modulation, and dysfunction of presynaptic muscarinic receptors are suggested as two possible mechanisms.

Effects of safflower oil and evening primrose oil in men with a low dihomo-gamma-linolenic level

Low levels of essential polyunsaturated fatty acids of the n-6 series are associated with coronary heart disease. Linoleic acid, but not gamma-linolenic acid requires the activity of delta 6-desaturase for its conversion to dihomo-gamma-linolenic and arachidonic acid. Evening primrose oil (EPO) and safflower oil (SO) are rich in linoleic acid, but EPO contains also 9% gamma-linolenic acid. The effect of EPO (10, 20 and 30 ml/day) and SO (20 ml/day) for 4 months on the deposition of linoleic acid metabolites in adipose tissue of 4 groups of 6-9 men with low adipose dihomo-gamma-linolenic acid was examined. EPO but not SO increased adipose dihomo-gamma-linolenic acid level from 0.080 +/- 0.005% to 0.101 +/- 0.005% (P less than 0.01; 20 ml/day for 4 months). Adipose dihomo-gamma-linolenic/linoleic acid ratio increased with EPO from 0.99 +/- 0.16 X 10(2) to 1.13 +/- 0.14 X 10(2) and fell on SO from 1.04 +/- 0.10 X 10(2) to 0.90 +/- 0.07 X 10(2) (P less than 0.01). Similar qualitative changes in the relative amount of dihomo-gamma-linolenic acid in serum triglyceride and cholesteryl ester fractions were observed. At the dose of 20 ml/day, SO and EPO did not differ in their effect on serum cholesterol (7.13 +/- 0.43 vs. 7.33 +/- 0.42 mmol/l (NS)), LDL-cholesterol (5.10 +/- 0.32 vs. 4.88 +/- 0.46 mmol/l (NS)) nor did the 2 oils differ in their effect on HDL-cholesterol. These results suggest that linoleic acid is not readily converted to dihomo-gamma-linolenic acid due to a low activity of delta 6-desaturase in these highly selected men. EPO was not an effective hypocholesterolaemic agent in this study.

Plasma antioxidants and coronary heart disease: vitamins C and E, and selenium

The possibility of a relation between plasma antioxidants such as vitamins C and E and selenium, and mortality from coronary heart disease (CHD) was examined. A cross-sectional survey was undertaken of random population samples of apparently healthy middle-aged men in four European regions with differing mortalities from CHD [rate/100,000 for men aged 40-49]: north Karelia (eastern Finland) (n = 99) [212/100,000]; south-west Finland (n = 85) [146/100,000]; Scotland (n = 131) [140/100,000]; and south Italy (n = 80) [43/100,000]. Median (5th-95th percentile) plasma vitamin C concentrations were lower in Scotland: 18.2 (5.7-61.3) microM than in other regions: north Karelia 28.4 (6.2-85.2); south-west Finland 33.5 (5.7-76.6); south Italy 38.0 (10.2-69.8) microM (P less than 0.001). The median levels in the four areas did not however reflect the regional CHD mortality rates. Regional differences in plasma vitamin E levels were also observed: Scottish levels were low 20.0 (12.1-29.3) microM (P less than 0.001) and did not differ between the other areas: 23.0 (16.7-35.1), 22.5 (13.7-31.6) and 23.9 (15.6-41.3) microM respectively. The vitamin E gradient could be explained in part by differences in serum cholesterol. However, cholesterol-adjusted vitamin E levels were low in the three high CHD areas: Scotland 3.41 (2.41-4.62); north Karelia 3.53 (2.67-5.18); south-west Finland 3.53 (2.58-4.92); Italy 4.81 (3.25-5.99) mumol/mmol cholesterol (P less than 0.001). Cholesterol-adjusted vitamin E was not lower in north Karelia, the higher CHD mortality area in Finland. Serum selenium values also varied with the area examined and reported low levels in Finland were confirmed. Nevertheless, selenium levels did not correlate with the reported mortality rates of CHD. Thus in our small cross-cultural study the evidence did not support our hypothesis that plasma antioxidants explain regional differences in CHD mortality.

Dietary fish oil and ischaemic arrhythmias

Ventricular fibrillation (VF), a serious arrhythmia, is an important cause of death from ischaemic heart disease. There is substantial evidence that experimental diets with a high polyunsaturated (linoleic acid) to saturated fatty acid ratio offer protection against VF. In this article the effects of large amounts of dietary fish oil (up to 30% cal) are reviewed. It is concluded that in all recently published studies marked increases in the incorporation of n-3 fatty acids in membranes was achieved. Two studies were too small, however, to demonstrate any statistically significant difference in VF. The results from a third, a long term feeding study, show a reduction in VF when compared with a highly saturated fat diet, but not when compared to a polyunsaturated fatty acid (n-6) rich diet. Using a more realistic fish oil supplement (0.4% cal) for 8 weeks, we observed a small but nonsignificant reduction in the incidence of VF during acute myocardial ischaemia in the isolated perfused rat heart. The need for further work on the effect of dose, dietary period and confounding influences of saturated fatty acids and linoleic acid are discussed.

Effects of Maxepa on serum lipids in hypercholesterolaemic subjects

The effect of dietary supplementation with 20 capsules/day Maxepa or olive oil on serum lipids has been studied in 21 hypercholesterolaemic patients using a double-blind crossover design. Platelet membrane eicosapentaenoic acid percentage rose by more than 10-fold after 2 months dietary supplementation with Maxepa. Total serum cholesterol was unchanged and there was a rise in LDL-cholesterol and HDL-cholesterol concentration in men, but no change in LDL-cholesterol, and a fall in HDL-cholesterol in women. In men and women there was a marked fall in total serum triglyceride, VLDL-triglyceride and VLDL-cholesterol levels. Thus, Maxepa is not an effective treatment for isolated hypercholesterolaemia.

Low plasma vitamins E and C. Increased risk of angina in Scottish men

Cross-cultural studies suggest that low plasma antioxidant levels contribute to the high incidence of coronary heart disease (CHD) in Scotland. One hundred twenty-five cases of angina without reported history were identified by a postal WHO chest pain questionnaire from a systemic population sample of 6000 Edinburgh men (35-54 years). Classical CHD risk factors (lipids, blood pressure, smoking, and relative weight), plasma vitamins, and a new independent CHD risk factor, adipose tissue linoleate, were measured in angina (n = 125) and healthy controls (n = 430). Cigarette smoking was common in angina (46% vs. 29%, p less than 0.01), and adipose tissue linoleate was lower (8.77 +/- 0.18% vs. 9.81 +/- 0.14% (p less than 0.01). Classical CHD risk factors were not different. Vitamin E/cholesterol molar ratio (micron/mM) was lower in angina than in controls: 1.58 +/- 0.03 vs. 1.66 +/- 0.02 (p less than 0.01). Plasma vitamin C was also lower in angina than in controls: 23.6 +/- 1.7 vs. 30.5 +/- 1.1 microM (p less than 0.001). The relative risk of angina for those in the lowest versus those in the highest quintile of the vitamin E/cholesterol ratio distribution was 2.2:1, irrespective of other risk factors (p less than 0.009). Adipose tissue linoleate removed the association between vitamin E and angina. The relative risk of angina for those in the lowest versus those in the highest quintile of plasma vitamin C was 2.6:1 (p less than 0.01), and the increased risk was also independent of classical risk factors, but closely related to a smoking habit. Low plasma vitamin E or adipose linoleate predisposes to angina, and smoking may increase the risk of angina by lowering plasma vitamin C levels in Scottish men.

Linoleic acid and coronary heart disease

Low tissue concentrations of the essential fatty acid, linoleic acid, occur in communities with high rates of coronary disease and in patients with angina and myocardial infarction. This relationship is independent of lipids and blood pressure, but in smokers linoleic acid is particularly low because they eat less linoleic acid-containing foods.