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atherosclerosis(ăth'ərōsklərō`sĭs): see arteriosclerosisarteriosclerosis
, general term for a condition characterized by thickening, hardening, and loss of elasticity of the walls of the blood vessels. These changes are frequently accompanied by accumulations inside the vessel walls of lipids, e.g.
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a chronic disease characterized by a thickening and loss of elasticity of the arterial walls and constriction of their lumina, followed by disruption of the blood supply of organs. It usually affects the entire arterial system, although in an uneven manner.
Atherosclerosis was once identified with arteriosclerosis. This identification was made as part of a concept which combined essentially different diseases—hence the incorrectness of the identification. Elderly people are the most frequent victims of atherosclerosis. The external manifestations of the disease are usually preceded by an asymptomatic period of many years’ duration. Atherosclerotic changes occur to some degree in many young people. Males suffer from atherosclerosis three to five times as often as females. A hereditary predisposition and individual characteristics of the organism are factors in the development of the disease. Diabetes mellitus, obesity, podagra, cholelithiasis, and other conditions also help to promote it. A diet rich in animal fats is a significant predisposing factor, but not a primary cause, of atherosclerosis. Other significant causal factors are physical inactivity, mental and emotional stress that traumatizes the nervous system, a strenuous tempo of life, noise, and certain working conditions.
Atherosclerosis develops as a result of a disturbance of the metabolism of lipides (fatlike substances), especially cholesterol, and changes in the structure and function of the vascular wall and the coagulative and anticoagulative systems. A disturbance of cholesterol metabolism increases blood cholesterol, which eventually becomes an important (though not essential) link in the development of the disease. In atherosclerosis there is apparently not only a decrease in the degree of utilization and excretion of excess food cholesterol but also an increased synthesis of it in the body. Metabolic disturbances are connected with disorders of the regulatory nervous and endocrine systems.
Atherosclerosis is characterized by the formation in the vascular wall of atherosclerotic plaques, more or less solid coatings of the innermost layer of the artery. At first the albuminous substance of this layer swells; then it becomes more permeable and cholesterol penetrates into the vascular wall. The accumulation of cholesterol in the arterial walls causes secondary changes in the vessels manifested by a proliferation of connective tissue. The atherosclerotic plaques then undergo several changes. They may break down to form a gruel-like substance (hence the name atherosclerosis), they may have calcium deposited in them (calcinosis), or a semitransparent homogeneous substance may be produced (hyaline). The process is progressive. The lumina of the vessels become narrow. Because of the circular arrangement of the plaques the vessels lose their capacity to dilate, and this in turn impairs the regulation of the blood supply to organs during strenuous work. Uneven-nesses within the vessels promote the formation of clots and thrombi, which aggravate the circulatory disorder to the point where circulation ceases entirely. The development of thrombi is also aided by a decrease in the intensity of the anticoagulation processes. Some investigators ascribe the development of atherosclerosis to the impairment of blood clotting and the accumulation of thrombotic masses in the vascular walls, followed by adiposis, loss of cholesterol, and connective tissue reaction.
If atherosclerotic changes are dominant in the blood vessels of the heart, brain, kidneys, or lower extremities, disturbances which determine the clinical picture of the disease will arise in the organ that suffers from an inadequate blood supply. Atherosclerosis of the cardiac vessels is manifested by coronary insufficiency or myocardial infarction. Cerebral atherosclerosis may result in the impairment of mental activity or, if pronounced, in paralysis of one kind or another. Atherosclerosis of the renal arteries is usually manifested by persistent hypertension. Atherosclerosis of blood vessels in the legs may cause intermittent claudication, ulcers, gangrene, and so forth.
Treatment and prevention. The treatment and prevention of atherosclerosis is aimed at regulating general and cholesterol metabolism. Efforts to normalize working and living conditions are of value—the observance of proper work and rest regimens, exercise, and so forth. The diet should not be rich, especially in animal fats and carbohydrates. It should include foods containing vitamins and vegetable oils. Physicians prescribe certain vitamins, hormones, and drugs that inhibit the synthesis of cholesterol and promote its excretion, as well as drugs that prevent clotting (anticoagulants) and dilate the blood vessels. Treatment must be strictly individualized and supervised by a physician.
REFERENCESIl’inskii, B. V. Ateroskleroz. Leningrad, 1960.
Miasnikov, A. L. Gipertonicheskaia bolezn’ i ateroskleroz. Moscow, 1965.
Glezer, G. A., and L. A. Miasnikov. Preduprezhdenie ateroskleroza. Moscow, 1966.
L. A. MIASNIKOV