AUTHOR AND EDITOR INFORMATION

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INTRODUCTION

Section 2 of 11  

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Background

Polygenic hypercholesterolemia (nonfamilial hypercholesterolemia is the preferred term) is the most common form of elevated serum cholesterol concentrations. Generally, nonfamilial hypercholesterolemia manifests as moderate hypercholesterolemia (240-350 mg/dL) with serum triglyceride concentrations within the reference range. However, practically speaking, the material in this article is also relevant to patients with mixed dyslipidemias with triglyceride levels of less than 350 mg/dL.

This condition is caused by a susceptible genotype aggravated by excessive saturated fat, trans fatty acid, and cholesterol intake (although the actual effect of cholesterol intake is small). The involved genes have yet to be discovered. Nonfamilial hypercholesterolemia is associated with an increased risk for coronary heart disease (CHD), as displayed in Image 1. Recent studies that show the efficacy of cholesterol-reduction strategies in the reduction of CHD events, even in patients with serum cholesterol concentrations of less than 240 mg/dL, suggest that lower cholesterol concentrations should be viewed as desirable.

The first guidelines of the US National Cholesterol Education Program (NCEP) were published in 1988 and revised in 1993 and 2001.

Pathophysiology

Low-density lipoprotein (LDL) particles are the major plasma carriers of cholesterol. Therefore, the serum cholesterol measurement is usually a surrogate for the low-density lipoprotein cholesterol (LDL-C) concentration, except in patients with excessive very low-density lipoprotein (VLDL) levels and chylomicron particles that manifest as high serum triglyceride levels. For a simplified diagram of cholesterol metabolism, see Image 2. Elevated LDL-C concentrations may be the consequence of elevated LDL production or decreased LDL cellular uptake. Diets high in saturated fat, trans fat, and cholesterol appear to cause a reduction in LDL receptors in the liver, thus retarding LDL catabolism.

Although the liver may directly secrete some LDL, whether increased direct hepatic LDL output is a factor in elevated LDL states is unknown. Overproduction of VLDL can obviously lead to increased LDL levels because VLDL is converted to LDL; however, many patients with elevated VLDL (triglyceride) levels have reduced LDL concentrations due to accelerated VLDL metabolism. Some patients with mixed dyslipidemias probably have nonfamilial hypercholesterolemia that manifests as elevated LDL-C concentrations and insulin resistance that manifests as low high-density lipoprotein cholesterol (HDL-C) levels, high triglyceride values, or both.

Frequency

United States

The guidelines of the American Heart Association and the NCEP Adult Treatment Panel III (ATP III) define hypercholesterolemia as a blood cholesterol concentration of greater than or equal to 240 mg/dL. Desirable cholesterol concentrations are less than 200 mg/dL. The National Health and Nutrition Examination Survey III, performed from 1988-1991, discovered that 26% of American adults had high blood cholesterol concentrations and 49% had desirable values. According to the NCEP ATP III guidelines, all adults aged 20 years or older should have a fasting lipid profile determined at least every 5 years to assess CHD risk. Sixty-five million American adults qualify for therapeutic lifestyle changes, while 36 million US adults need pharmacologic therapy to reach NCEP ATP III goals.

International

Serum cholesterol concentrations vary widely throughout the world. Generally, countries associated with low serum cholesterol concentrations (eg, Japan) have lower CHD event rates, while countries associated with very high serum cholesterol concentrations (eg, Finland) have very high CHD event rates. However, some populations with similar total cholesterol levels have very different CHD event rates, suggesting that other factors also influence CHD risk.

Mortality/Morbidity

The primary manifestation of hypercholesterolemia is increased CHD risk. Data from epidemiological studies (eg, the Multiple Risk Factor Intervention Trial and the Framingham Heart Study) show a relationship between an increase in serum cholesterol concentrations and CHD events and CHD mortality rates. Recent studies have shown that CHD morbidity and mortality can be reduced with therapies that lower serum LDL-C levels. More recent data also suggest a relationship between thrombotic, but not hemorrhagic, stroke rates and serum cholesterol concentrations; furthermore, recent data indicate that therapy with statins reduces atherothrombotic stroke risk in patients with CHD.

Race

Among adults, National Health and Nutrition Examination Survey III data (1988-1992) show more frank hypercholesterolemia among non-Hispanic white persons (19%) than Mexican Americans (15%) or non-Hispanic black persons (16%).

Sex

Hypercholesterolemia is more common in men younger than 55 years and in women older than 55 years.

Age

Hypercholesterolemia increases with advancing age in adults (see Image 3).

CLINICAL

Section 3 of 11  

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History

Hypercholesterolemia is usually discovered during routine screening and does not produce symptoms. Hypercholesterolemia is more common in individuals with a family history of the condition, but lifestyle factors (eg, a diet high in saturated fat) clearly play a major role.

Physical

Tendon xanthomas are not present in persons with nonfamilial hypercholesterolemia. If tendon xanthomas are present, familial hypercholesterolemia or familial defective apoprotein B-100 is the correct diagnosis. Eruptive xanthomas signify extreme hypertriglyceridemia. Xanthelasma may be present but does not necessarily indicate hypercholesterolemia. Secondary hypercholesterolemia is suggested by stigmata of liver disease, hypothyroidism, hypopituitarism, nephrotic syndrome, and chronic renal disease.

Causes

Several drugs and disease states are associated with hypercholesterolemia; however, for the overwhelming majority of patients, the Western lifestyle of a high-fat diet superimposed on a susceptible genotype appears to cause hypercholesterolemia. Nonetheless, ensuring that the patient does not have untreated hypothyroidism, renal disease, or liver disease is important. Furthermore, progestins, anabolic steroids, and glucocorticoids may adversely affect low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) values.

The risk factors for coronary heart disease (CHD), other than LDL-C, in the US National Cholesterol Education Program (NCEP) screening and treatment algorithm are as follows:

• Age and sex
  
  
  • Men aged 45 years or older
  
  
  
  • Women aged 55 years or older
     
• Family history of premature CHD (male first-degree relative <55 y, female first-degree relative <65 y)



• Current cigarette smoking



• Hypertension - Blood pressure greater than or equal to 140/90 mm Hg or current antihypertensive drug therapy



• Low HDL-C concentration - Less than 40 mg/dL, but 1 risk factor subtracted if HDL-C concentration is more than 60 mg/dL (This level has been increased from <35 mg/dL compared with the value from the NCEP Adult Treatment Panel II [NCEP ATP II].)

DIFFERENTIALS

Section 4 of 11  

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Other Problems to be Considered

Biliary cirrhosis
Coronary heart disease

WORKUP

Section 5 of 11  

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Lab Studies

• The US National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) suggests screening asymptomatic individuals with a fasting lipid panel every 5 years.



• Practically speaking, performing a risk factor analysis prior to obtaining screening blood test results is preferable. Patients can have risk factors for coronary heart disease (CHD) other than low-density lipoprotein cholesterol (LDL-C; see Causes).
• • A full lipid profile is obtained after the patient fasts for 9-12 hours.
  
  
  
  • Chylomicrons must be absent and the total triglyceride level must be less than 400 mg/dL in order to use the Friedewald formula to calculate LDL-C. The Friedewald formula is LDL-C = total cholesterol - high-density lipoprotein cholesterol (HDL-C) + triglycerides/5.
  
  
  
  • Direct LDL-C measurements do not offer any greater use, except in patients with marked hypertriglyceridemia. Direct LDL-C measurements can be performed while the patient is in the nonfasting state.
     
• To perform a careful medical evaluation, the practitioner must ascertain all medication intake (both prescription and over-the-counter medications) and perform tests of serum thyroid-stimulating hormone, liver function, creatinine, and urinalysis to rule out secondary dyslipidemias.

TREATMENT

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Medical Care

During the 1990s, the cholesterol revolution occurred. Numerous studies documented the efficacy of low-density lipoprotein cholesterol (LDL-C) reduction in the reduction of coronary heart disease (CHD) events and, in some situations, the reduction of both CHD and total mortality rates.

• Medical therapy involves lifestyle modification and pharmacologic therapy.
  
  
  • For patients with known atherosclerosis (clinical CHD, symptomatic carotid artery disease, peripheral arterial disease, or abdominal aortic aneurysm), the LDL-C goal is less than 100 mg/dL, although an LDL-C goal of less than 70 mg/dL is now considered a therapeutic option in patients considered to be at very high risk (acute coronary syndrome patients, diabetes mellitus, multiple risk factors with uncorrected risk factors such as continued smoking).
  
  
  
  • For patients with 2 or more risk factors, the LDL-C goal is less than 130 mg/dL, with recommendations for drug therapy that depend on the estimated 10-year risk of a CHD event based on the modified Framingham equation (see below).
  
  
  
  • For patients at low risk (0-1 risk factors), the LDL-C goal is less than 160 mg/dL.
  
  
  
  • The LDL-C goal for patients with CHD equivalent risk, including patients with diabetes mellitus, should also be less than 100 mg/dL. In patients considered to be very high risk, a goal of less than 70 mg/dL is an acceptable option
     
• The evaluation generally begins with a risk-factor analysis. Patients are then categorized according to CHD or CHD risk equivalent (particularly diabetes), ie, those with multiple risk factors and those at low risk (<2 risk factors). Patients with CHD or CHD equivalent risk have a greater than 20% 10-year risk for CHD events. Low-risk patients generally have a 10-year CHD risk of less than 10%. Patients with multiple risk factors may or may not be at high risk.



• The new National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) guidelines recommend calculating a Framingham risk score in patients with multiple risk factors to quantify risk and set LDL-C goals. The Framingham score calculator is available through the NCEP and the US National Heart, Lung, and Blood Institute (see Risk Assessment Tool for Estimating 10-year Risk of Developing Hard CHD).
  
  
  • Patients with CHD or CHD equivalent are prescribed drug therapy simultaneously with therapeutic lifestyle changes if their LDL-C concentration is greater than or equal to 130 mg/dL. Drug therapy is optional for patients whose LDL-C value is 100-129 mg/dL.
  
  
  
  • For patients with multiple risk factors, the LDL-C level at which drug treatment is recommended depends on the Framingham score. The LDL-C goal is less than 130 mg/dL. For patients with multiple risk factors and a 10-year risk of greater than 20%, the treatment is similar to that of patients with CHD. For patients with a 10-year risk of 10-20%, drug treatment is considered if their LDL-C level is greater than or equal to 130 mg/dL. For patients with multiple risk factors and a 10-year risk of less than 10%, drug therapy is considered if their LDL-C levels are greater than or equal to 160 mg/dL.
  
  
  
  • For patients at low risk, the LDL-C goal is less than 160 mg/dL, with therapeutic lifestyle changes for patients with higher values and drug therapy considered at LDL-C levels of greater than or equal to 190 mg/dL.
  
  
  
  • Therapeutic lifestyle treatment (ie, dietary changes and exercise) is recommended for patients whose LDL-C concentrations are greater than their goal LDL-C.

• The new NCEP guidelines also recommend trying to identify patients with what has been called the metabolic syndrome. Such patients in particular should be targeted for therapeutic lifestyle changes. These patients meet at least 3 of the following criteria:
  
  
  • Abdominal obesity (waist >40 in for men, >35 in for women)
  
  
  
  • High triglyceride level (>150 mg/dL)
  
  
  
  • Low high-density lipoprotein cholesterol (HDL-C) value (<40 mg/dL for men, <50 mg/dL for women)
  
  
  
  • High blood pressure (>130/85 mm Hg)
  
  
  
  • Impaired fasting glucose (IFG) value (plasma glucose level >110 mg/dL, although the lower limit now generally used in the American Diabetes Association IFG cutpoint of 100 mg/dL or greater)
     
• If the patient's serum triglyceride level remains greater than or equal to 200 mg/dL after the LDL-C goal is reached, a secondary non–HDL-C goal is set. The non–HDL-C goal is the LDL-C goal plus 30 mg/dL. This goal may be achieved with an increase in the statin dose, a more efficacious statin, or the addition of another agent (eg, fibrate, niacin, fish oil). Fenofibrate has less of a propensity for drug interactions; therefore, it is preferred in most situations. If fish oil is used, the correct dose is at least 2-3 g of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) daily. Because most 1-g fish oil capsules contain only approximately 300 mg of DHA and EPA, a patient must consume 10 1-g fish oil capsules daily to reach the goal. More highly concentrated fish oil capsules or liquids can be used, but the patient usually cannot find these in local pharmacies.



• Screen all patients via a fasting lipid profile every 5 years beginning at age 20 years. Patients with CHD should undergo a lipid profile determination at least yearly. Patients with multiple risk factors should have their lipid profiles determined at least every other year.



• In 3 months, recheck the lipid profiles of patients treated with therapeutic lifestyle intervention. In 6-12 weeks, recheck the lipid profiles of patients treated with drugs.



• Liver function testing is indicated periodically for patients taking statins or fibrates, although the risk for hepatotoxicity is very low. Liver function abnormalities are more common at the highest doses of each of the approved statins. Checking liver test results 6-12 weeks after an increase in the dose is reasonable, particularly in patients on high-dose statins.



• The dosage and approximate LDL-C lowering of various statins is as follows:
  
  
  • For atorvastatin at 10-80 mg/d, the LDL-C level is lowered by 39-60%.
  
  
  
  • For fluvastatin at 20-80 mg every bedtime or 40 mg twice daily, the LDL-C level is lowered by 22-36%.
  
  
  
  • For lovastatin at 20-40 mg every evening or 40 mg twice daily, the LDL-C level is lowered by 24-42%.
  
  
  
  • For pravastatin at 10-80 mg every bedtime, the LDL-C level is lowered by 22-34%.
  
  
  
  • For rosuvastatin at 5-40 mg/d, the LDL-C level is lowered by 45-63%.
  
  
  
  • For simvastatin at 20-80 mg every bedtime, the LDL-C level is lowered by 38-47%.

Diet

The NCEP has created dietary guidelines for all people older than 2 years. The reduction of saturated fat intake is vitally related to reduced LDL-C levels. In general, replacing fat with complex carbohydrates is helpful. Because carbohydrates are less calorically dense than fat, this substitution may also help prevent obesity. Adopting an appropriate diet may help patients reduce their LDL-C value by approximately 10-15%. However, in real-world studies, a 5% reduction is more likely. Reduction in trans fat intake also helps reduce LDL-C levels and may help raise HDL-C levels.

• NCEP dietary guidelines are as follows:
• • Total fat - Less than 30% of energy intake (calories)
  
  
  
  • Saturated fat - Less than 7% of energy intake
  
  
  
  • Polyunsaturated fat - Less than or equal to 10% of energy intake
  
  
  
  • Monounsaturated fat - From 10-15% of energy intake
  
  
  
  • Cholesterol - Less than 200 mg/dL
  
  
  
  • Carbohydrates - From 50-60% of energy intake
     
• Extreme fat and cholesterol restriction has been achieved with vegetarian diets, as demonstrated by the 1990 studies performed by Ornish and colleagues. This type of dietary restriction has resulted in a marked reduction in LDL-C levels and improvement in CHD symptoms. Whether these dietary restrictions are realistic for most Americans is debatable. Moreover, such a diet also reduces HDL-C levels and raises triglyceride levels.



• Plant sterols and plant stanol esters can be included in the diet and may reduce LDL-C values by approximately 10-15%. Commercial preparations are available as margarine substitutes (eg, Benecol, Take Control).



• Recently, after years of lay promotion, small, short-term (6 mo) studies have suggested that high-fat low-carbohydrate diets (eg, the Atkins diet) may facilitate weight loss without adversely affected serum lipid concentrations. However, the long-term effects of such diets remain to be determined.

Activity

Although exercise has little effect on LDL-C concentrations, aerobic exercise may improve insulin sensitivity, HDL-C concentrations, and triglyceride levels and, thus, may help reduce CHD risk. Patients who exercise and adhere to an appropriate diet appear to be more successful in long-term lifestyle modifications that improve their CHD risk profile.

MEDICATION

Section 7 of 11  

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The statin (HMG-CoA reductase inhibitor) class of drugs has revolutionized the treatment of hypercholesterolemia. Statins are highly efficacious and very well tolerated. Thus, other drugs are often not needed for low-density lipoprotein cholesterol (LDL-C) reduction.

Drug Category: Statins

Recent studies show the efficacy of statin drugs in reducing coronary heart disease (CHD) events, CHD death, and total mortality rates (see Images 4-5). Efficacy for LDL-C lowering at approved doses of statins is listed in Medical Care under Dosage and approximate LDL-C lowering of various statins. Primary prevention implies the use of statins in an asymptomatic population, which may include some people with clinically occult disease. Secondary prevention implies the use of statins in patients with clinically apparent disease.

The Scandinavian Simvastatin Survival Study (4S) was the first study to show significant reduction (compared with placebo) in the all-cause mortality rate (30%), in CHD events (34%), and in the CHD mortality rate (42%). In addition, subjects with CHD (secondary prevention) who were treated for moderate hypercholesterolemia (eg, treatment with simvastatin, mean dose 27 mg/d) maintained total cholesterol levels of less than or equal to 201 mg/dL for 5.4 years, which was the median follow-up period.

The West of Scotland Coronary Prevention Study (WOSCOPS) studied high-risk male subjects who had no history of CHD events (primary prevention). Pravastatin was administered at a dose of 40 mg/d for 4.9 years. Cardiovascular events were reduced by 31%, and the treatment caused a borderline statistically significant reduction of 31% in the total mortality rate compared with placebo.

The Cholesterol and Recurrent Events (CARE) study of subjects with CHD and cholesterol concentrations within the reference range (mean LDL-C level of 138 mg/dL) examined the effects of pravastatin at a dose of 40 mg/d. Compared with placebo, the CHD events were reduced by 24% at 5 years, with no significant change in total mortality.

The Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TexCAPS) enrolled more than 6000 subjects with average LDL-C concentrations and below-average high-density lipoprotein cholesterol (HDL-C) values. Lovastatin was administered at a dose of 20-40 mg/d for approximately 5 years, resulting in a 37% reduction in first major acute coronary events compared with placebo therapy.

The Long-Term Intervention with Pravastatin in Ischaemic Disease (LIPID) study used pravastatin at a dose of 40 mg/d for an average of 6.2 years in subjects with CHD; the CHD mortality rate decreased by 24%, and the total mortality rate decreased by 22% compared with placebo treatment.

The Atorvastatin versus Revascularization Treatment (AVERT) study compared 80 mg atorvastatin daily with standard therapy and angioplasty in subjects with CHD. Although event rates at 18 months were the same between both groups, the time until the first CHD event was longer, with aggressive LDL-C lowering. Angioplasty alone has not been proven to prevent events, so this is not necessarily tantamount to a no-therapy comparison trial.

The Myocardial Ischemia Reduction with Aggressive Cholesterol Lowering (MIRACL) trial showed borderline significant reduction in coronary events in subjects treated with atorvastatin (80 mg/d) who presented with an acute coronary syndrome, although significant abnormalities revealed via liver function test were common. The major positive finding from this study was a 61% reduction in stroke in the atorvastatin-treated group.

In the Pravastatin in Elderly Individuals at Risk of Vascular Disease (PROSPER) study that compared pravastatin 40 mg/d versus placebo in subjects aged 70-82 years with a history of CHD or risk factors for CHD, active therapy reduced cardiovascular events by 15%.

The Medical Research Council/British Heart Foundation Heart Protection Study (HPS) assessed the effects of simvastatin (40 mg/d) versus placebo in approximately 20,000 subjects with vascular disease or at high risk for CHD with total cholesterol levels greater than 135 mg/dL, including approximately 6000 subjects with diabetes mellitus. CHD endpoints were reduced by approximately 24% and were effective in multiple subgroups, including subjects with diabetes. The mortality rate was reduced by approximately 15%.

The Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) used 10 mg of atorvastatin versus placebo in approximately 10,000 subjects with hypertension. CHD event rates were reduced approximately 36%. However, most subgroups, including subjects with diabetes mellitus or metabolic syndrome, did not return positive results, perhaps because of the short duration (3.3 y) of the study.

The Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial compared treatment with atorvastatin (80 mg) with treatment with pravastatin (40 mg) in subjects with CHD. After 18 months, the atorvastatin treatment group had a slight decrease in atheroma volume based on intravascular ultrasonography evaluations, and the pravastatin group had a slightly increased atheroma volume.

The Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) study also compared atorvastatin therapy (80 mg/d) with pravastatin therapy (40 mg/d) in subjects who had been hospitalized for acute coronary syndromes. The baseline LDL-C level was approximately 106 mg/dL. After a mean follow-up of 2 years, the intensively treated group had LDL-C levels of approximately 62 mg/dL, compared with approximately 95 mg/dL in the pravastatin group. Cardiovascular events were reduced by 16%.

Unfortunately, the study had a dropout rate of approximately one third. The number of patients needed to treat was 26, but the number needed to cause transaminase values to exceed 3 times the upper limit of normal was only 46 patients. In this scenario, 26 patients would have to be treated to prevent one clinical event, and 46 patients would have to be treated to see one case of transaminases >3 X ULN (and possibly end up stopping therapy). Interestingly, subjects pretreated with statins or those with baseline LDL-C levels of less than 125 mg/dL did not show a benefit from high-dose atorvastatin therapy compared with pravastatin therapy (40 mg).

The Treating to New Targets (TNT) study assessed the effect of therapy with atorvastatin 80 mg/d versus atorvastatin 10 mg/d in patients with stable CHD for a period of 4.9 years. The mean on-treatment LDL-C level was 77 mg/dL in the former group and 101 mg/dL in the latter group. The relative risk of cardiovascular events was reduced by 22%. Mortality was higher but not significantly statistically different in the high-dose atorvastatin group, although persistent transaminase elevations were 6 times higher in this group.

The statins lower LDL-C by inhibiting HMG-CoA reductase, the enzyme that regulates the rate-limiting step in cholesterol synthesis. The amount of the intermediate (ie, mevalonate) is lowered, and, subsequently, cholesterol levels are reduced in hepatic cells. This, in turn, results in up-regulation of LDL receptors and increased hepatic uptake of LDL from the circulation.

Drug Category: Antilipemic agent, fibric acid

Older fibrates (eg, clofibrate, gemfibrozil) are used primarily for triglyceride lowering. The Helsinki Heart Study, published in 1987, showed a decrease in CHD events in patients with elevated non–HDL-C concentrations when used in primary prevention. With the advent of statins, fibrates have largely fallen out of favor when pure LDL-C lowering is needed. However, fenofibrate is more efficacious for LDL-C lowering than earlier fibrates. Ongoing studies may help determine if fenofibrate is useful in patients with mixed dyslipidemia, particularly subjects with type 2 diabetes mellitus. The Diabetes Atherosclerosis Intervention Study showed that such subjects with CHD have stabilization of angiographic findings when treated with fenofibrate compared with placebo. This trial was inadequately powered to assess an effect on CHD events. Currently, fenofibrate should probably be relegated to second-line therapy for LDL-C reduction in patients intolerant of statins.

The recent publication of the Veterans Affairs HDL Intervention Trial is notable. This trial consisted of male subjects with CHD, relatively low LDL-C concentrations (mean of 112 mg/dL), and low HDL-C concentrations (mean of 32 mg/dL). Coronary events were reduced 22% with gemfibrozil treatment compared with placebo treatment. This effect was thought to be due to an increase (6%) in HDL-C levels; however, the almost 30% decrease in triglyceride levels in subjects treated with gemfibrozil may also have played a role in risk reduction.

Drug Category: Bile acid sequestrants

These agents are also called resins. Bile acid sequestrants are used primarily as additional therapy in patients with familial hypercholesterolemia who experience inadequate LDL-C lowering with statins. These agents are also useful in pediatric hypercholesterolemia. Several studies show that LDL-C lowering with resins retards the progression of atherosclerosis. The Lipid Research Clinics Coronary Primary Prevention Trial showed that cholestyramine therapy could reduce the risk for CHD events.

Interference with anionic drug absorption and patient compliance are major problems with this class of drugs. Resins may be used as an adjunct in primary hypercholesterolemia. These drugs form a nonabsorbable complex with bile acids in the intestine, which, in turn, inhibits enterohepatic reuptake of intestinal bile salts.

Drug Category: Antilipemic agents, miscellaneous

Formulated to maximize the benefit of 2 drugs, perhaps at a lower dose than might maximally be used, in one formulation to achieve maximal lipid alterations. No clinical endpoint trials have been completed using these preparations.

Drug Category: Cholesterol absorption inhibitors

Inhibit dietary cholesterol absorption.

Drug Category: Vitamins

Niacin lowers LDL-C and triglycerides and raises HDL-C, making it very attractive for lipid modification; however, patient tolerability and toxicity greatly limit use. Niacin has been shown to be useful in retarding progression of atherosclerosis and reducing CHD events when used in conjunction with a bile acid sequestrant or lovastatin. Niacin is the only agent to lower lipoprotein (a), but niacin increases insulin resistance and raises homocysteine levels, which may be deleterious to cardiovascular risk. This agent is probably most useful for the reduction of triglyceride levels and the elevation of HDL-C levels, particularly in patients with mixed dyslipidemia or marked hypertriglyceridemia.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Deterrence/Prevention

• Obviously, the adoption of a healthier lifestyle that included aerobic exercise and a low-fat diet would probably reduce the prevalence of obesity, hypercholesterolemia, and, ultimately, the risk of coronary heart disease (CHD). Hopefully, younger Americans will adopt these measures to reduce CHD events in the coming years.

Prognosis

• The statin era has revolutionized the treatment of hypercholesterolemia. Coupled with the treatment of hypertension and the use of beta-blockers, angiotensin-converting enzyme inhibitors, and aspirin, the potential for reduction of CHD events in patients with known atherosclerosis is significant.



• Cholesterol reduction is certainly useful as a CHD risk-reduction strategy and for primary prevention in individuals who are at high risk for CHD or other forms of atherosclerosis.

Patient Education

• Dietary education about a low-fat (especially saturated fat and trans fat), low-cholesterol diet is of paramount importance.



• For excellent patient education resources, visit eMedicine's Cholesterol Center and Statins Center. Also, see eMedicine's patient education articles High Cholesterol, Understanding Your Cholesterol level, Lifestyle Cholesterol Management, Understanding Cholesterol-Lowering Medications, and Statins and Cholesterol.

MISCELLANEOUS

Section 9 of 11  

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• Miscellaneous
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Medical/Legal Pitfalls

• High total cholesterol levels can be due to a very high high-density lipoprotein cholesterol (HDL-C) level, particularly in women. If the low-density lipoprotein cholesterol (LDL-C) level is not elevated, no treatment is needed.



• Patients with marked hypertriglyceridemia (>1000 mg/dL) have very high cholesterol concentrations (300-600 mg/dL), but this situation is due to large numbers of chylomicrons and very low-density lipoprotein (VLDL), not LDL. Therefore, do not treat these patients with statins; treat them with agents that lower triglycerides (eg, fibrates, niacin, fish oils).



• Obtain serum thyroid-stimulating hormone levels, liver function test results, creatinine values, and urinalysis results to help rule out secondary dyslipidemias.

Special Concerns

• Therapeutic controversies
  • Post hoc analysis of some studies (eg, Cholesterol and Recurrent Events, West of Scotland Coronary Prevention Study) has been interpreted to indicate the presence of a lower limit for LDL-C, and, beyond this level, lowering the LDL-C is no longer beneficial. Similar analyses of other studies (eg, Scandinavian Simvastatin Survival Study, Air Force/Texas Coronary Atherosclerosis Prevention Study) have failed to indicate an LDL-C therapeutic threshold.
  
  
  
  • The Medical Research Council/British Heart Foundation Heart Protection Study enrolled subjects at high risk for CHD and total cholesterol (not LDL-C) concentrations greater than 135 mg/dL. CHD event reduction was observed in the total patient population and in the subgroup with the lowest tertile of LDL-C.
  
  
  
  • The recently completed Pravastatin or Atorvastatin Evaluation and Infection Therapy trial showed CHD event reduction when postacute coronary syndrome patients were treated with atorvastatin at 80 mg/d (LDL-C level at treatment was approximately 62 mg/dL) compared with pravastatin at 40 mg/d (LDL-C level at treatment was approximately 95 mg/dL). The study was plagued by high dropout (approximately one third of subjects in both groups at 2 y), and the fact that liver function test abnormalities (transaminase levels >3 times the upper limit normal) were common. The number needed to treat to prevent a CHD event was 26, and the number needed to treat to potentially harm (transaminases >3 times the upper limit normal) was 45.
  
  
  
  • The Post Coronary Artery Bypass Graft Trial showed less progression of the disease in bypass grafts with attainment of an LDL-C value of approximately 95 mg/dL (achieved with lovastatin) compared with less aggressive treatment, with an LDL-C value of approximately 135 mg/dL.
  
  
  
  • The Reversal of Atherosclerosis with Aggressive Lipid Lowering trial showed minimal regression of atherosclerosis in CHD subjects treated with 80 mg of atorvastatin for 18 months compared with minimal progression in CHD subjects treated with 40 mg of pravastatin.
  
  
  
  • The Atorvastatin versus Revascularization Treatment trial showed no difference in CHD events in patients treated to achieve an LDL-C level of approximately 77 mg/dL compared with patients with an LDL-C level of approximately 115 mg/dL who had angioplasty.
  
  
  
  • The Treating to New Targets Study showed a reduction in cardiovascular events, but not mortality, in patients with stable CHD who were given atorvastatin 80 mg/d compared with atorvastatin 10 mg/d (LDL-C 77 mg/dL vs 101 mg/dL). Persistent transaminase elevations were 6 times as common in the former group.
  
  
  
  • Because the epidemiologic data suggest a curvilinear relationship between LDL-C values and CHD events, an LDL-C level below which no benefit may accrue is probable; however, that actual level is unknown. The National Cholesterol Education Program (NCEP) guidelines probably provide an adequate estimate of an appropriate LDL-C target, except perhaps in patients with diabetes. 
• • The author believes that lower targets (<70 mg/dL) may be reasonable in patients who can be treated with low-to-moderate dose statin. However, the author feels that the risk/benefit ratio for high-dose statin (atorvastatin 80 mg/d is what has been tested so far) across the board to try to achieve an LDL-C level of less than 70 mg/dL (many patients will not achieve this level despite this therapy) is not yet proven definitely to be acceptable and achieve extra added benefit. The question of achieving lower LDL-C values with combination therapy (statin plus ezetimibe), in terms of showing further CHD risk reduction, remains unanswered at this point.
  
  
  
  • Whether patients with low HDL-C and high LDL-C values should use a drug (eg, niacin) to raise their HDL-C levels, in addition to using a drug to lower LDL-C levels, is questionable. The HDL Atherosclerosis Treatment Study showed positive effects of low-dose (10 mg) simvastatin and niacin on angiographic measures. However, no outcome studies have been performed with more conventionally used doses of statins. Statins often raise HDL-C levels a small amount. Some statin trials show a marked diminution of increased CHD risk in patients treated with statins who have lower HDL-C levels compared with individuals with higher HDL-C levels. The results of the Veterans Affairs HDL Intervention Trial may not be applicable to patients with high baseline LDL-C concentrations.
     
• Patients with mixed dyslipidemias
  
  
  • Patients with insulin resistance and those with type 2 diabetes mellitus are likely to have mild-to-moderate triglyceride elevations.
  
  
  
  • Whether lipid therapy beyond statins is beneficial is debatable, although combination therapy with statins plus niacin or fibrates improves lipid parameters. Such therapy clearly increases the potential for adverse effects. The author believes that most patients should be treated with monotherapy. If a fibrate is given with a statin, fenofibrate is probably safer than gemfibrozil.
  
  
  
  • A potentially more benign nutraceutical is fish oil. The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) lower triglyceride levels if at least 3 g/d is administered. Unfortunately, many preparations contain large amounts of fish oil that is not DHA or EPA. These preparations just supply fat, with little positive effect on the lipid profile. The author always insists on personally examining the fish oil bottle that his patients use to ensure that such patients will benefit from this therapy.
     
• Women who are postmenopausal
  
  
  • Although epidemiologic studies have suggested that estrogen therapy is associated with better lipid profiles and lower CHD risk, recent intervention trials with estrogen have generated considerable controversy.
  
  
  
  • Currently, therapy with estrogens plus progestins is considered potentially harmful long-term therapy in postmenopausal women. This drug combination may still be useful for short-term therapy soon after menopause for vasomotor symptoms in women with an intact uterus.
  
  
  
  • In women who do not have a uterus, therapy with estrogen alone is of no proven benefit for CHD prevention.
  
  
  
  • Statin therapy, rather than estrogens, should be used for primary lipid modification and for CHD prevention in women who are postmenopausal, particularly in women with atherosclerosis. 
     
• Patients with diabetes
  
  
  • The post hoc analysis of the Scandinavian Simvastatin Survival Study (4S) trial in patients with type 2 diabetes mellitus showed dramatic event reduction in patients who received simvastatin. Unfortunately, this trial did not include patients with high triglyceride levels, which is a common lipid abnormality in persons with type 2 diabetes mellitus.
  
  
  
  • The Medical Research Council/British Heart Foundation Heart Protection Study (of simvastatin 40 mg/d) showed a similar reduction in CHD event rates in patients with type 2 diabetes mellitus compared with patients without diabetes.
  
  
  
  • Recent epidemiologic work suggests that patients with diabetes who have not had a previous known myocardial infarction may be at the same risk for CHD events and mortality as patients with diabetes who have not had a previous known myocardial infarction compared with patients without diabetes who have had a previous coronary event. These data led the American Diabetes Association to advocate an LDL-C level of less than 100 mg/dL for patients with diabetes. American Diabetes Association treatment based on LDL-C levels is as follows:
    
    
    • Medical nutrition therapy
      
      
      • Patients without coronary heart disease, peripheral vascular disease, or cardiovascular disease and an LDL-C level of greater than 100 mg/dL: Goal level of LDL-C is less than 100 mg/dL (<70 mg/dL is considered an option).
      
      
      
      • Patients with coronary heart disease, peripheral vascular disease, or cardiovascular disease and an LDL-C level higher than 100 mg/dL: Goal level of LDL-C is less than 100 mg/dL (<70 mg/dL is considered an option).
         
    • Drug treatment
      
      
      • Patients without coronary heart disease, peripheral vascular disease, or cardiovascular disease and an LDL-C level higher than 130 mg/dL: Goal level of LDL-C is less than 100 mg/dL. Additionally, for patients with diabetes who have multiple CHD risk factors (eg, low HDL-C level, hypertension, smoking, family history of cardiovascular disease, microalbuminuria or proteinuria), most authorities recommend drug therapy for LDL-C levels of 100-130 mg/dL. Age and sex are not risk factors because women and men have equal CHD risk.
      
      
      
      • Patients with CHD, peripheral vascular disease, or cardiovascular disease and an LDL-C level of greater than 100 mg/dL: Goal level of LDL-C is less than 100 mg/dL (goal of <70 mg/dL is an option).
         
  • The NCEP ATP III now considers diabetes mellitus a CHD risk equivalent, with the same LDL-C goal (<100 mg/dL, or if considered appropriate, <70 mg/dL) as patients with known CHD. 
     
• Risk of myopathy
  
  
  • With statin monotherapy, the risk of myopathy is low and is increased with the concomitant use of fibrates, niacin, macrolides, protease inhibitors, and imidazoles. The fibrate effect appears to relate to inhibition of glucuronidation of statins, rather than an effect on cytochrome P450 metabolism, because it is observed with all statins.
  
  
  
  • Routine CK monitoring has no proven value in the prevention of myopathy. Because muscle aches are common, even in placebo-treated patients, a check of serum CK values, once the patient has myalgias, may be helpful. Many patients with myalgias have CK values within the reference range.
  
  
  
  • Sometimes, changing the statin is necessary to eliminate the problem. Anecdotal reports suggest that coenzyme Q supplements in patients with muscle aches and CK values within the reference range may reduce myalgias.
  
  
  
  • Recent reports suggest that histologic myopathy may occur in the absence of CK elevations. Whether this is a widespread phenomenon is debatable.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Relative risk of coronary heart disease (CHD) mortality versus baseline serum cholesterol over time in 3 large cohorts of young men. CHA is Chicago Heart Association Detection Project in Industry, PG is Chicago Peoples Gas Company, and MRFIT is Multiple Risk Factor Intervention Trial. Adapted from Stamler, 2000.
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Media type:  Graph

Media file 2:  Simplified diagram of cholesterol metabolism. LDL is low-density lipoprotein, VLDL is very low-density lipoprotein, IDL is intermediate-density lipoprotein, HDL is high-density lipoprotein, and LPL is lipoprotein lipase.
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Media type:  Graph