The arteries become narrowed when fatty substances, such as cholesterol, that are carried in the blood accumulate on the inside lining of the arteries and form yellow deposits called atheroma. These deposits restrict blood flow through the arteries. In addition, the muscle layer of the artery wall becomes thickened, narrowing the artery even more. Platelets (tiny blood cells responsible for clotting) may collect in clumps on the surface of the deposits and initiate the formation of blood clots.
A large clot may completely block the artery, resulting in the organ it supplies being deprived of oxygen. There are usually no symptoms in the early stages of atherosclerosis. Later, symptoms are caused by reduced or total absence of a blood supply to the organs supplied by the affected arteries. If the coronary arteries, which supply the heart muscle, are partially blocked, symptoms may include the chest pain of angina.
If there is complete blockage in a coronary artery, a sudden, often fatal, heart attack may occur. Many strokes are a result of atherosclerosis in the arteries that supply blood to the brain. If atherosclerosis affects the leg arteries, the 1st symptom may be crampingpain when walking due to poor blood flow to the leg muscles. If the condition is associated with an inherited lipid disorder (see hyperlipidaemias), fatty deposits may develop on tendons or under the skin in visible lumps.
The risk of developing atherosclerosis is determined largely by the level of cholesterol in the bloodstream, which depends on dietary and genetic factors. Athersclerosis is most common in Western countries, where most people eat a diet high in fat. Some disorders such as diabetes mellitus can be associated with
a high cholesterol level regardless of diet.
Blood flow through an artery can be investigated by angiography or Doppler ultrasound scanning. The best treatment for atherosclerosis is to prevent it from progressing by following a healthy lifestyle. This includes eating a low-fat diet, not smoking, exercising regularly, and maintaining the recommended weight for height.
These measures lead to a lower-than-average risk of developing significant atherosclerosis. People found to have high blood cholesterol but who are otherwise in good health will be advised to adopt a low-fat diet. They may also be given drugs that decrease blood cholesterol levels (see lipid-lowering drugs).
For people who have had a heart attack, research has shown that there may be a benefit in lowering blood cholesterol levels, even if the level is within the average range for healthy people. People who have atherosclerosis and are experiencing symptoms of the condition may be prescribed a drug such as
aspirin to reduce the risk of blood clots forming on the damaged artery lining.
Surgical treatment such as coronary angioplasty (see angioplasty, balloon) may be recommended for those people thought to be at high risk of severe complications. If blood flow to the heart is severely obstructed, a coronary bypass operation to restore blood flow may be carried out.
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