INTRODUCTION
Hyperlipidaemia has
emerged as one of the most important preventable and
modifiable risk factors for coronary heart disease (CHD).
Clinical signs of this condition are an increase in the
fasting serum cholesterol level (hypercholesterolaemia)
or the fasting serum triglyceride level
(hypertriglyceridaemia) or both. A meta- analysis of 16
randomised trials involving cholesterol-lowering
interventions reported a 2.5% reduction in CHD incidence
for every 1% cholesterol reduction. Lipid levels may be
affected by diet, exercise, smoking, certain medications
(e.g : beta blockers, thiazide diuretics,
glueocorticoids) and concurrent disease states (e.g .
kidney and liver diseases).
LIPIDS
AND LIPOPROTEINS
The major plasma lipids
include cholesterol, triglycerides and phospholipids.
Lipoproteins are
macromolecular
complexes that play an important role in the transport
and metabolism of lipids. Lipoproteins have been
classified on the basis of their densities into five
major classes, chylomicrons, very low density
lipoproteins (VLDL), intermediate density lipoproteins
(IDL), low-density lipoproteins (LDL) and high-density
lipoprotelm (HDLP).
LIPID CONCENTRATIONS AND CHD
•Total
cholesterol (TC) is a sum of HDL cholesterol, LDL
cholesterol and 20% of the triglyceride value. TC level
is an excellent predictor of CHD. Since
atheroselerosis begins early in life cholesterol levels
in young adults predict CHD risk 30 to 40 years later.
Cholesterol measurement will thus reduce the long-term
risk for CHD.
•Although
the role of high triglycerides as an independent factor
in the development of CHD remains controversial, data
from several prospective studies suggest that
triglycerides are probably an important risk factor.
Hypertriglyceridaemia is often associated with increased
plasminogen activator inhibitor levels and impaired
fibrinolysis. This is especially of importance in the
Indian context since triglyceride levels are considered
to be significantly elevated in Indians. However, recent
data show that cholesterol levels are also significantly
elevated in the Indian population.
The
relation between VLDL and CHD is unclear at present.
However, elevated VLDL levels occur quite commonly in
persons afflicted by premature CHD. Moreover, VLDL gives
rise to LDL, which has been undoubtedly proven to be
atherogenic.
•LDL
cholesterol is highly atherogenic, hence high levels of
LDL increase the risk of CHD.
LDL = TC - (HDL + triglyceride/5)
•HDL
cholesterol has been found to be inversely related to
subsequent development of CHD, i.e. as HDL cholesterol
increases, CHD risk decreases.
•Cardiac
risk ratio i.e. Total cholesterol/ HDL, is an extremely
potent predictor of CHD
•Lp
(a), an LDL particle to which a large plasminogen-like
protein, termed apo(a) has been linked via a disulfide
bond is an atherogenic lipoprotein. There has been
speculation that apo(a) could competitively inhibit the
binding of plasminogen to its reeeptor and thus decrease
plasmin formation and thrombolysis.
DIAGNOSIS
The NCEP recommends that aduIts above
20 years shouid have total cholesterol and HDL measured
at least once every five years.If these levels are
abnormal, a lipoprotein
analysis
which measures 12 hours fasting total cholesterol,
HDL and triglyceride is recommended. TC and LDL levels
may be reduced by illness, inflammation, surgery and
trauma. Hence, the measurements should be repeated after
the illness has subsided. Patients at higher risk should
be tested more often.
CONCLUSION
Effective
control of the blood lipid levels reduced cardiovascular
morbidity and mortality both in patients with established
CHD and in those at risk of developing CHD. Hence
knowledge of the various aspects of the lipid profile and
the significance of each of the parameters is vital and
is essential part of management of CHD and people at risk
of CHD.
Drugs that reduce blood cholesterol
levels also cut heart patients' long-term risk of dying.
Researchers now report that aggressive treatment to
reduce blood fats (lipids) in patients with chest pain or
those who have just had a heart attack can reduce their
risk of dying by as much as 60%.
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