Coronary heart disease and risk factor modification. Is there a threshold?

Coronary artery disease regression. Convincing evidence for the benefit of aggressive lipoprotein management

BACKGROUND

Numerous reports suggest that coronary artery disease can regress with lipoprotein manipulation. Many of these reports lack control groups and contain relatively small numbers.

METHODS AND RESULTS

Ten randomized controlled clinical trials using coronary arteriography to assess the effect of lipoprotein manipulation on the rate of progression and regression of atherosclerosis have been either published or reported as an abstract at a national meeting. These studies were critically reviewed for individual differences and combined clinically applicable lessons. These trials involved a total of 2095 subjects and have consistently reported reduction in the percentage of patients arteriographically defined as progressing (mean, 23.6%) and an increase in the percentage regressing (mean, 20.0%) compared with control groups. Compared with large clinical trials using clinical end points, lipoprotein change was greater, achieving on average a 28% reduction in low-density lipoprotein cholesterol, 11% reduction in triglycerides, and 11% increase in high-density lipoprotein cholesterol compared with control groups. Four investigations used a nonpharmacological approach, and seven used single and multiple drug therapy combined with diet. Despite the relatively brief treatment time of often 2 to 4 years, clinical events were fewer in the treatment groups; within some studies, this reached statistical significance. Side effects from the different therapies were tolerated by most patients, and severe adverse clinical events were few.

CONCLUSIONS

These trials present convincing evidence that aggressive lipoprotein manipulation can result in improved arteriographic measurements and fewer cardiovascular events in a relatively short period of time of 2 to 4 years. Extrapolation of this information to the larger population with known coronary artery disease suggests that directed lipoprotein manipulation can reduce clinical events in a cost-effective manner.

Low-intensity endurance exercise training, plasma lipoproteins and the risk of coronary heart disease

Physically active individuals generally show a reduced risk of coronary heart disease (CHD) compared to the sedentary population. However, whether such reduction in CHD risk mainly results from the concomitant improvement in cardiorespiratory fitness or from the alterations in CHD risk factors has yet to be clearly established. Furthermore, there is still some controversy regarding the potential associations between endurance training-induced changes in metabolic variables considered as CHD risk factors (plasma glucose, insulin and lipoprotein levels) and the magnitude of improvement in cardiorespiratory fitness. From the results of several studies discussed in this article, it is proposed that prolonged endurance exercise of low intensity (approximately 50% VO2max), performed on an almost daily basis, seems to significantly improve metabolic variables considered as CHD risk factors through mechanisms that are likely to be independent from the training-related changes in cardiorespiratory fitness. The notion of 'metabolic fitness' is introduced and can be defined as the state of a ste of metabolic variables relevant to CHD risk and affected by the level of physical activity. Evidence available suggests that these metabolic variables are not closely related to the adaptation of cardiorespiratory fitness in response to exercise training. The concept of metabolic fitness has several implications for the prescription of exercise and for the primary and secondary prevention of CHD. Indeed, emphasis should not be placed on aiming at increasing VO2max through high-intensity exercise, but rather on producing a substantial increase in daily energy expenditure that will eventually lead to weight loss and related improvements in carbohydrate and lipid metabolism. Therefore, from a practical standpoint, although a 1 h daily walk may not have marked effects on cardiorespiratory fitness, it probably represents an exercise prescription that is likely to substantially improve 'metabolic fitness', thereby reducing the risk of CHD.

Drug therapy and the prevention of atherosclerosis in humans

The results of the World Health Organization Cooperative Trial, the Coronary Drug Project, the Coronary Primary Prevention Trial and the Helsinki Heart Study indicate that clinical expression of coronary artery disease can be delayed with pharmacologic modification of plasma lipoproteins. Change in coronary artery disease can be semiquantitated by repeat arteriograms. Three randomized clinical trials indicate that rate of progression of atherosclerosis, as defined by arteriography, can be reduced, and existing lumen obstruction decreased. Tendon xanthomas occur in hypercholesterolemia, and reduction in xanthoma size with drug therapy suggests an improved atherosclerotic disease state. The clinician has a variety of pharmacologic therapies available. The role of bile acid-binding resins, fibric acid derivatives, hydroxymethylglutaryl coenzyme A reductase inhibitors, nicotinic acid and antioxidants is each unique. Understanding the role of lipoproteins in atherosclerosis will help in selecting the most appropriate therapy for each individual patient. Medications not designed for their lipoprotein effects can significantly alter lipoproteins. Medications, such as nonselective beta blockers, can alter low-density lipoprotein (LDL) subclass distribution with no change in LDL cholesterol content. Such changes may eradicate part of the beneficial cardiovascular effect of beta blockade therapy. In the future, therapeutic choices may depend in part on lipoprotein abnormalities such as lipoprotein (a), apolipoprotein E isoforms, hyperapobetalipoproteinemia, LDL.

Smoking accounts for adverse effect of antihypertensive medications on plasma lipids. A population-based study

Mean plasma levels of total cholesterol, high density lipoprotein cholesterol, total-to-high density lipoprotein cholesterol ratio, and total triglycerides were determined in a representative sample of the adult Israeli Jewish population, excluding known diabetics and individuals with overt atherosclerotic morbidity (n = 1,153). Levels were compared in normotensive and untreated and treated hypertensive individuals by glucose tolerance category and smoking, after adjustment for sex, age, and body mass index. In the presence of normal glucose tolerance, lipid levels in the nonsmoking normotensive and treated hypertensive groups were similar, whereas in the smoking, treated hypertensive group, lipids were significantly affected, as indicated by the respective adjusted mean levels (mg/dl): total cholesterol, 219, 221, and 240; high density lipoprotein cholesterol, 45.0, 43.6, and 42.0; ratio, 5.2, 5.3, and 6.0; and triglycerides, 114, 107, and 144. In individuals with glucose intolerance, trends were the same with the exception of triglycerides, which were significantly elevated in the nonsmoking, treated hypertensive group also; the respective values were 217, 225, and 257 for total cholesterol; 45.1, 44.9, and 41.4 for high density lipoprotein cholesterol; 5.2, 5.5, and 6.8 for the ratio; and 133, 152, and 187 for triglycerides. Lipid disturbances in treated smokers were not due to heavier smoking or differences in dietary intake. We conclude that disturbance of plasma lipid profile in treated hypertensive individuals may be mainly due to an interaction with smoking, with an additional effect of glucose intolerance.

A review of combined hyperlipidaemia and its treatment with fenofibrate

Approximately 15% of myocardial infarction survivors less than 60 years of age have a plasma lipid abnormality defined as combined hyperlipidaemia. Patients with this condition are at substantial risk for future cardiovascular events. Combined hyperlipidaemia involves elevations in both plasma triglycerides and low-density lipoprotein (LDL) cholesterol and may share similarities with hyperapolipoproteinaemia, LDL-pattern B and the small LDL-pattern. Treatment is directed at reduction of LDL-cholesterol and plasma triglyceride values. Nicotinic acid and the fibric acid derivatives are useful therapeutic agents. Fenofibrate is a fibric acid derivative that lowers both triglycerides and LDL-cholesterol in combined hyperlipidaemia. In combined hyperlipidaemia, fenofibrate has been shown to reduce significantly plasma triglycerides by approximately 40%, LDL-cholesterol by 6%, and to increase high-density lipoprotein cholesterol by 15%. Apoproteins are favourably altered with increases in apoprotein-A, decreases in apoprotein-E and inconsistent decreases in apoprotein-B. Fenofibrate is well tolerated with primarily dermatological side-effects.

The Role of Diet, Exercise, and Medication in Blood Lipid Management of Cardiac Patients

In brief: Results of clinical investigations clearly indicate that aggressive management of blood lipids and lipoproteins can significantly benefit cardiovascular health. This finding is particularly important for patients with diagnosed coronary heart disease and those at risk for developing it. Therapy comprises reduction of excess body fat, a diet low in cholesterol and saturated fats, endurance exercise, and medication. Drugs that affect blood lipid levels include beta-blockers, bile acid binding resins, fibric acid derivatives, hydroxymethylglutaryl-coenzyme A reductase inhibitors, nicotinic acid, and probucol. These can be used singly or in combination to bring about the desired lipid profile.

Blood cholesterol treatment attitudes of community physicians: a major problem

Blood cholesterol treatment attitudes of community physicians are an important component of the NIH recommendation to reduce blood cholesterol. To determine current blood cholesterol treatment attitudes, a survey of 2413 multispecialty Northern California physicians was conducted. A total of 793 physicians responded. Results show that treatment habits among medical specialties are similar with a tendency for lower initial treatment levels in the subspecialties of endocrinology and cardiology. No specialty or subspecialty group indicated an aggressive plasma lipid treatment attitude. The findings include the following: Mean values at which physicians reported treating hypercholesterolemia with medication (312 +/- 44 mg/dl) exceed the NIH definition of "high risk." Younger physicians treated hypercholesterolemia with diet at significantly lower blood cholesterol levels than did older colleagues (p = 0.04). Physicians exposed to the CPPT-LRC investigation did not show a difference in treatment attitudes with regard to blood cholesterol levels when compared to physicians without such an experience. The type of lipid-lowering medication used differs significantly among medical specialties and subspecialties. Physicians lack confidence in the precision of laboratory measurement of plasma lipids. Physician treatment attitudes require substantial change if the NIH cholesterol consensus conference goals are to be achieved.

Modification of plasma cholesterol through exercise. Rationale and recommendations

Until relatively recently, clinical information regarding plasma lipoproteins and their association with human atherosclerosis had been based on epidemiologic evidence obtained from cross-sectional studies or prospective studies that used clinical events as end points. Authorities have cautioned against the interpretation of these results to imply that drug therapy be used to alter the high-density lipoprotein (HDL) fraction of total cholesterol. Several recent investigations strongly suggest that decreasing the low-density lipoprotein fraction of total cholesterol and increasing the HDL fraction may alter the progression of atherosclerosis. Appropriate exercise may be a viable tool to assist in elevating plasma HDL levels.