To this list of conditions which are proven risk factors may be added many others, often associated with dyslipidaemia and with a higher than normal risk of coronary artery disease (CAD).
These include hypothyroidism, some forms of renal disease, pregnancy and alcohol abuse in susceptible people – and many more rare examples.
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Treatment is directed at the condition itself rather than primarily with a view to preventing CAD. The increased lipid levels in pregnancy decrease to normal once the baby is delivered.
Additional emerging risk factors include increased homocysteine levels, clotting disorders and stress.
Increased homocysteine levels
Homocysteine or hCys is an amino acid normally present in the body. How much is present is determined by the availability of its precursor, methionine, but more so by the enzymes involved in its formation and removal and by three vitamins: folic acid, vitamin B12 and vitamin B6.
A number of rare, major genetic abnormalities affecting its "removal" pathway can result in very high hCys concentrations which lead to lesions in the blood vessels and premature coronary disease. The picture is not identical to that of the usual form of atherosclerosis.
What is more important to the general reader is that there is some evidence that relatively low increases in hCys also increase the risk of CAD. This risk is thought to be similar to that conveyed by raised lipid levels.
These increases result from subtle gene defects and possibly low levels of the vitamins involved in hCys metabolism. It’s not currently known whether vitamin supplementation in people with low hCys levels decreases their risk of CAD. Trials are underway to establish this.
Detection of such mild disturbances can be made by measuring hCys levels.
Clotting disorders Thrombosis (clotting) within atherosclerotic plaque is an important cause of plaque progression and the development of physical symptoms of CAD.
There is normally a balance between preventing blood loss after injury and preventing spontaneous clotting with blockage of the affected vessel or movement of the clot to vessels elsewhere in the body. This balance is upset under some circumstances.
Obesity, cigarette smoking, the insulin resistance syndrome, salt intake, dyslipidaemias, hormonal contraceptive agents and oestrogen preparations as well as certain inherited traits are among the more important factors which promote blood clotting.
Conversely, exercise, loss of weight, reduced salt intake, aspirin and related medications reduce clotting.
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