Aetiology of CHD

Risk Factors

There are numerous factors that contribute to the development of Coronary Heart Disease. Its high prevalence and mortality means that the public need to be aware of the contributary risks. They are outlined on the following page:

-Risk Factors associated with CHD

Atherosclerosis

The main cause of CHD is atherosclerosis which leads to the narrowing of arteries. This is caused by the build-up of a lipid-based plaque in the coronary arteries, known as an atheroma. This development of an atheroma in these arteries is known as atherosclerosis.Although, these plaques develop over many years.

As an atheroma increases in size, it causes the lumen size of a coronary artery to decrease. When this happens, there may be insufficient oxygen supply - due to reduced blood flow - to the cardiac muscle cells, causing a condition called ischaemia. This can give pains of angina. If the plaque ruptures, it can cause an inflammatory response leading to clot formation. The clot can completely block the artery. When this happens, cardiac muscle cells may die leading to a heart attack - myocardial infarction.

CHD can be avoided, or at least the risk can be reduced by several factors. Some factors are controllable, some are non-controllable. More detail about atherosclerosis development can be found on the following page:

- Process of Atherosclerosis in CHD

Chlamydia infection

On going research investigate whether infection by Chlamydia pneumoniae could be a cause of CHD, independent of atherosclerosis. It is thought that the Chlamydia bacterium can incorporate proteins on its cell surface that are near-identical to some of the protein molecules on the body's own cells. This can, but not always, fool the immune system causing an unwanted response - an autoimmune response. One immune mechanism is an inflammatory response in the coronary arteries, leading to ischaemia.

Other infectious agents that are thought to cause CHD are Herpes virii and Helicobacter pylori. However, it must be stressed that these infections by these are not confirmed causes and still being investigated.

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