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Lipid
Disorders
General
Considerations
In recent years, a great deal of emphasis has been placed on
the relationship between elevated serum cholesterol
levels—especially low-density lipoprotein cholesterol (LDL-C)—and
the incidence of coronary artery disease (CAD).
Hyperlipidemia represents a public health epidemic that
continues to parallel the increased prevalence of obesity
and is intimately implicated in the development of CAD. It
is estimated that approximately 100 million American adults
have total serum cholesterol levels in excess of 200 mg/dL
and more than 12 million adults would qualify for
lipid-lowering therapy by current national standards.
Lowering LDL levels through diet and medication has been
shown to reduce the progression of CAD and CAD mortality.
According to the Framingham study, a 10% decrease in
cholesterol level is associated with a 2% decrease in
incidence of CAD morbidity and mortality.
Clinical
Findings
A history of lipid disorders should be sought in all routine
evaluations and in patients with suspected or overt
cardiovascular disease. Many individuals already know they
have high cholesterol levels from screening tests performed
at shopping malls, in other physicians' offices, or during
prior hospitalization. A family history of premature
cardiovascular disease is also useful. A history compatible
with overt cardiovascular disease, especially in a young man
or a premenopausal woman is highly suggestive of a
lipoprotein disorder. In addition, a history or symptoms of
other diseases associated with lipoprotein abnormalities (eg,
diabetes mellitus, hypothyroidism, end-stage renal disease)
should be sought (Table 2–2). Other risk factors for CAD
should also be identified because they multiply the risk
caused by lipid disorders
Treatment
The rationale of treatment of hyperlipidemia is based on the
hypothesis that abnormalities in lipid and lipoprotein
levels are risk factors for CAD and that changes in blood
lipids can decrease the risk of disease and complications.
Levels of plasma cholesterol and LDL have consistently been
shown to directly correlate with the risk of CAD. Since the
promulgation of the previous NCEP (Adult Treatment Panel II)
guidelines, the results of numerous studies involving the
primary and secondary prevention of CAD with
3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase
inhibitors have been reported. These trials have
overwhelmingly demonstrated a significant reduction in CAD
events, CAD mortality, and mortality from all other causes,
in addition to ameliorating LDL-C, HDL-C, and triglyceride
levels. Data from the West of Scotland Coronary Prevention
Study and from the Air Force/Texas Coronary Atherosclerosis
Prevention Study have provided cogent evidence that primary
prevention of CAD in hypercholesterolemic individuals
reduces the incidence of coronary events and, in the former
study, death from cardiovascular events. Secondary
prevention trials such as the Scandinavian Simvastatin
Survival Study (4S) and Long-Term Intervention with
Pravastatin in Ischemic Disease (LIPID) study have revealed
that lowering LDL cholesterol levels can retard the
progression of coronary atherosclerosis and reduce CAD
events, CAD mortality, and cerebrovascular events. These
compelling data have prompted a more aggressive approach to
the treatment of hyperlipidemia, culminating in the new NCEP
(Adult Treatment Panel III [ATP III]) guidelines (Table
2–4). Although ATP III maintains attention to intensive
treatment of patients with CAD, its major new focus is on
primary prevention in patients with multiple risk factors
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