Your Cholesterol Profile - In Depth (cont.)
What are LDL cholesterol particle size patterns A and B?
LDL patterns A and B refer to the size of LDL cholesterol particles in the
blood. Some doctors believe that small LDL cholesterol particles in the blood
may pose a greater risk for developing atherosclerosis and heart attacks than
the absolute level of LDL cholesterol in the blood. The size of LDL cholesterol
particles is primarily inherited. A special blood test called polyacrylamide
gradient gel electrophoresis can measure particle size and determine whether a
person has blood cholesterol LDL pattern A or LDL pattern B.
Persons with LDL cholesterol pattern A have large, buoyant LDL cholesterol
particles. Individuals with pattern A are more likely to have normal blood
levels of LDL cholesterol, HDL cholesterol, and triglycerides. Pattern A is
usually not associated with an increased likelihood of atherosclerosis.
Persons with LDL cholesterol pattern B have predominantly small and dense LDL
cholesterol particles. Pattern B is frequently associated with low HDL
cholesterol levels, elevated triglyceride levels, and the tendency to develop
high blood sugar levels and type II diabetes mellitus.
Individuals with pattern B are also more likely to develop high blood
triglyceride levels after a fatty meal (postprandial hyperlipidemia). Pattern B
is associated with accelerated atherosclerosis and a 3 to 5- fold increase in
heart attack risk. Pattern B is believed to be the most important cause of
atherosclerosis in people with normal or near normal total and LDL cholesterol
levels.
Some scientists believe that the smaller LDL particles are more dangerous
than the larger ones because they can more easily squeeze through the tiny gaps
between the cells in the endothelium to reach inside the artery walls. The
endothelium is a thin layer of cells which covers the inner wall of the
arteries. The cells making up the endothelium have tiny gaps between them.
Others postulate that the smaller LDL cholesterol particles are more easily
oxidized. Oxidation of cholesterol is significant in the formation of
cholesterol plaques.
How can LDL cholesterol size be enlarged?
Even though LDL cholesterol particle size is mainly genetically inherited,
individuals who have small LDL particles (pattern B) can increase their particle
size through diet, exercise, and medications.
Diets that are low in saturated fat and cholesterol, regular aerobic
exercise, and loss of excess body fat have been determined to decrease the
number of small LDL particles and increase the number of large LDL particles in
the blood. In other words, lifestyle modifications can change pattern B to
pattern A.
When lifestyle changes alone are unsuccessful, medications can be used. Even
though the statin medications (discussed above) are effective in lowering the
absolute levels of LDL cholesterol, they appear to have a limited effect on LDL
cholesterol size pattern. Medications such as nicotinic acid (niacin) and
gemfibrozil (Lopid) have been found effective in many instances in increasing
the size of LDL cholesterol particles.
What is lipoprotein (a), (Lp(a)) cholesterol?
Lipoprotein (a) (Lp(a)) is an LDL cholesterol particle that is attached to a
special protein called apo(a). In large part, a person's level of Lp(a) in the
blood is genetically inherited. Elevated levels of Lp(a) (higher than 20 mg/dl
to 30 mg/dl) in the blood are linked to a greater likelihood of atherosclerosis
and heart attacks in both men and women. The risk is even more significant if
the Lp(a) cholesterol elevation is accompanied by high LDL/HDL ratios.
Certain diseases are associated with elevated Lp(a) levels. Patients on
chronic kidney dialysis and those with nephrotic syndromes (kidney diseases that
cause leakage of blood proteins into the urine) tend to have high levels of
Lp(a).
There are many theories as to how Lp(a) causes atherosclerosis although
exactly how Lp(a) accumulates cholesterol plaques on the artery walls has not
been well defined. Clinical trials conclusively proving that lowering Lp(a)
reduces atherosclerosis and the risk of heart attacks have not been conducted.
Currently, there is no international standard for determining Lp(a) cholesterol
levels and commercial sources of Lp(a) testing may not have the same accuracy as
research laboratories. Therefore, specifically measuring and treating elevated
Lp(a) cholesterol levels are not widely performed in this country.
How can Lp(a) cholesterol levels be reduced?
Most lipid-lowering medications such as statins, Lopid, and cholestyramine
have a limited effect in lowering Lp(a) cholesterol levels. Estrogen has been
shown to lower Lp(a) cholesterol levels by approximately 20% in women with
elevated Lp(a) cholesterol. Estrogen can also increase HDL cholesterol levels
when given to postmenopausal women. Additionally, nicotinic acid (Niacin or
Niaspan) in high doses has been found to be effective in lowering Lp(a)
cholesterol levels by approximately 30%.
Next: Who should undergo standard lipid profile testing? »
- Statins - Read about statins, cholesterol lowering medications like Levacor, Zocor, Pravachol, Lipitor, Crestor, and more. Side effects, drug interactions, and patient information is also provided.
- Electrocardiogram (ECG or EKG) - Read about the Electrocardiogram (ECG, EKG) procedure used to reflect underlying heart conditions such as agnina, occurance of a prior heart attack or of an evolving heart attack, and more.
- Heart Attack - Overview on heart attack (myocardial infarction) and heart attack symptoms including jaw pain, headache, shortness of breath, nausea, vomiting, heartburn, sweating, and more.
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