hypertension(redirected from White coat effect)
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high blood pressure,elevated blood pressureblood pressure,
force exerted by the blood upon the walls of the arteries. The pressure in the arteries originates in the pumping action of the heart, and pressure waves can be felt at the wrist and at other points where arteries lie near the surface of the body (see pulse).
..... Click the link for more information. resulting from an increase in the amount of blood pumped by the heart or from increased resistance to the flow of blood through the small arterial blood vessels (arterioles). Hypertension is generally defined as a blood pressure reading greater than 140 over 90; presssures of 120–139 over 80–89 are now considered prehypertension. When the cause is unknown, the hypertension is called primary, or essential, hypertension. When a cause can be identified (e.g., a disorder of the adrenal glands, kidneys, or arteries), the condition is known as secondary hypertension. Factors such as heredity, obesity, smokingsmoking,
inhalation and exhalation of the fumes of burning tobacco in cigars and cigarettes and pipes. Some persons draw the smoke into their lungs; others do not. Smoking was probably first practiced by the indigenous peoples of the Western Hemisphere.
..... Click the link for more information. , and emotional stress are thought to play a role; the usual immediate cause is an imbalance in the body's vasoconstriction/fluid retention systems, often involving a decrease in the kidney's secretion of the regulatory hormone, renin.
Known as the "silent killer," hypertension often produces few overt symptoms; it may, however, result in damage to the heart, eyes, kidneys, or brain and ultimately lead to congestive heart failurecongestive heart failure,
inability of the heart to expel sufficient blood to keep pace with the metabolic demands of the body. In the healthy individual the heart can tolerate large increases of workload for a considerable length of time.
..... Click the link for more information. , heart attack (see infarctioninfarction,
blockage of blood circulation to a localized area or organ of the body resulting in tissue death. Infarctions commonly occur in the spleen, kidney, lungs, brain, and heart.
..... Click the link for more information. ), kidney failure, or strokestroke,
destruction of brain tissue as a result of intracerebral hemorrhage or infarction caused by thrombosis (clotting) or embolus (obstruction in a blood vessel caused by clotted blood or other foreign matter circulating in the bloodstream); formerly called apoplexy.
..... Click the link for more information. . African Americans and women are the most affected. Treatment of hypertension includes diets to reduce weight and salt and alcohol intake, increased exercise, quitting smoking, and various drugs, such as diureticsdiuretic
, drug used to increase urine formation and output. Diuretics are prescribed for the treatment of edema (the accumulation of excess fluids in the tissues of the body), which is often the result of underlying disease of the kidneys, liver, lungs, or heart (e.g.
..... Click the link for more information. , ACE inhibitorsACE inhibitor
or angiotensin-converting enzyme inhibitor
, drug used to reduce elevated blood pressure (see hypertension), to treat congestive heart failure, and to alleviate strain on hearts damaged as a result of a heart attack (see infarction).
..... Click the link for more information. , beta-blockersbeta-blocker
or beta-adrenergic blocking agent
, drug that reduces the symptoms connected with hypertension, cardiac arrhythmias, angina pectoris, migraine headaches, and other disorders related to the sympathetic nervous system.
..... Click the link for more information. , calcium-channel blockerscalcium-channel blocker,
any of a class of drugs used in treating hypertension, angina pectoris, and certain arrhythmias. They prevent the calcium ions needed for muscle contraction from entering the cells of smooth and cardiac muscle.
..... Click the link for more information. or angiotensin-receptor blockers, as well as biofeedbackbiofeedback,
method for learning to increase one's ability to control biological responses, such as blood pressure, muscle tension, and heart rate. Sophisticated instruments are often used to measure physiological responses and make them apparent to the patient, who then tries
..... Click the link for more information. . Many patients require a combination of drugs to control their blood pressure. Treatment for persons with prehypertension includes dietary and other lifestyle changes. Recent research has questioned the importance of dietary salt as a major contributor to hypertension; some studies point to low calcium intake as a cause.
See also eclampsiaeclampsia
, term applied to toxic complications that can occur late in pregnancy. Toxemia of pregnancy occurs in 10% to 20% of pregnant women; symptoms include headache, vertigo, visual disturbances, vomiting, hypertension, and edema.
..... Click the link for more information. .
a disease of the cardiovascular system, the principal manifestation of which is the elevation of blood pressure.
Hypertension was first described by the Soviet scientist G. F. Lang in 1922. The causes of its onset have not as yet been thoroughly elucidated. There are two points of view about the origin of hypertension. The first proceeds from the fundamental role played by the impairment of the nervous regulation of vascular tone together with a number of factors that predispose to the disease. These factors include hereditary deficiency in the hormonal mechanisms that regulate the state of the vascular system, previous kidney disease that has impaired circulation in them, changes in the blood vessels (especially of the brain and kidneys) through aging, and endocrine disturbances accompanying the climacteric.
Nervous and psychic tension and chronic overexhaustion, which with resistant humoral mechanisms cause no pathological changes, lead to spasm of the arterioles and elevation of blood pressure in the presence of predisposing factors. Increased tone in the muscles of the blood vessels (arterioles), with which the rise in blood pressure is associated, is connected with activation of the renin-angiotensin system (a group of biologically active substances whose interaction causes blood pressure elevation), with increased content in the blood of the hormone aldosterone, with a change in sodium metabolism, and with changes in blood circulation in the brain and kidney. All these changes are in turn associated with impairment of the nervous regulation of the processes described.
The second point of view proceeds from the role of the pressor (tending to increase blood pressure) and depressor factors of the kidney in the elevation of arterial blood pressure. The kidney contains the so-called juxtaglomerular apparatus, which stimulates formation of the pressor factor —renin. Renin, in turn, specifically stimulates formation by the adrenal cortex of a second factor—aldosterone— which regulates water metabolism and metabolism of potassium and sodium ions and influences the content of these elements in the smooth muscles of the blood vessels. Increase of sodium content in the smooth muscles of the vessels increases their tone, which in turn determines the elevation of blood pressure. Simultaneously, aldosterone blocks the paths of sodium elimination from the body. Thus, the renal factor may in itself induce blood pressure elevation. However, the kidney also possesses depressor properties, which lower blood pressure. Exhaustion of these properties may lead, in the opinion of advocates of the kidney theory, to the predominance of pressor activity and the development of hypertension.
The incidence of hypertension increases with age. Up to age 40, males are more frequently affected; after 40, morbidity among men and women is practically identical. Hypertension is one of the most common diseases of the cardiovascular system in the urban population, among which it is found at nearly three times the rate for the rural population. Persons most often affected are those whose work is to a large degree associated with nervous and psychic tension, such as engineering and technical personnel, workers in precision production, and workers in communications and transportation.
Hypertension is divided into three stages, according to the course and character of the clinical picture. Characteristic of the first, “transitory,” stage is short-term elevation of blood pressure, usually arising after overexhaustion or excessive nervous tension. The blood pressure quickly normalizes itself, without the use of special medications, under the influence of rest or of sedative preparations. During this period patients complain of increased nervous irritability, headaches, dizziness, and palpitations. Some enlargement of the heart and sometimes a systolic murmur at the apex may be noted; on the electrocardiogram there may be some indications of beginning myocardial hypertrophy. The second stage is divided into two phases. Characteristic of the first phase (labile hypertension) is vacillation of the blood pressure from minor elevation to rather high levels. In the second phase (stable hypertension) the blood pressure stands permanently at high levels. Illnesses in which blood pressure is lowered by rest and the use of ordinary sedatives are included in the first phase. In the second stage, in addition to the characteristic symptoms of hypertension, such as ringing in the ears, dizziness, headaches, and palpitations, signs may appear of cardiac insufficiency (dyspnea, edema, tachycardia, and arrhythmia) and coronary insufficiency (pain behind the sternum and in the region of the heart and development of myocardial infarction).
The third stage is characterized by the development of arteriolosclerosis, with renal impairment, cardiac failure, and cerebrovascular affection against a background of high and persistent hypertension. Development of renal failure, cicatricial changes in the myocardium, and disruption of blood supply to the brain are also possible in this stage.
Hypertensive crises, which represent brief exacerbations of the disease, may be distinguished in the course of hypertension; sudden, sharp elevation in blood pressure accompanied by headaches, dizziness, vomiting, tachycardia, chills, and, occasionally, impairment of vision are characteristic. Disruptions of coronary and brain circulation are also possible (myocardial infarction or cerebral apoplexy).
In the first stage of hypertension, treatment involves sufficient sleep, elimination of nervous, psychic, and physical overloads, prohibition of alcoholic beverages and smoking, and use of sedatives. In the later stages, medications that lower blood pressure, tranquilizers, and sleep-inducing drugs are prescribed, together with an appropriate diet. Surgical treatment has not been widely used. Elimination, where possible, of excessive emotional stress and psychic trauma, rational organization of the work and rest regime, and sufficient sleep are recommended for prevention.
REFERENCESLang, G. F. Gipertonieheskaia bolezn’. [Leningrad] 1950.
Miasnikov, A. L. Gipertonicheskaia bolezn’. Moscow, 1954.
Miasnikov, A. L., and K. N. Zamyslova. “Gipertonicheskaia bolezn’.” In Mnogotomnoe rukovodstvo po vnutrennim bolez-niam, vol. 2. Edited by E. M. Tareev. Moscow, 1964.
E. I. CHAZOV