Mar 20, 2017

Hypertension (HTN)


High blood pressure; transitory or sustained elevation of systemic arterial blood pressure to a level likely to induce cardiovascular damage or other adverse consequences. Hypertension has been arbitrarily defined as a systolic blood pressure above 140 mmHg or a diastolic blood pressure above 90 mmHg. Consequences of uncontrolled hypertension include retinal vascular damage (Keith-Wagener-Barker changes), cerebrovascular disease and stroke, left ventricular hypertrophy and failure, myocardial infarction, dissecting aneurysm, and renovascular disease. An underlying disorder (e.g., renal disease, Cushing syndrome, pheochromocytoma) is identified in fewer than 10% of all cases of hypertension. The remainder, traditionally labeled “essential” hypertension, probably arise from a variety of disturbances in normal pressure-regulating mechanisms (which involve baroreceptors, autonomic influences on the rate and force of cardiac contraction and vascular tone, renal retention of salt and water, formation of angiotensin II under the influence of renin and angiotensin-converting enzyme, and other factors known and unknown), and most are probably genetically conditioned. Syn: hyperpiesis, hyperpiesia.


Because of its wide prevalence and its impact on cardiovascular health, hypertension is recognized as a major cause of disease and death in industrialized societies. It is estimated that 24% of the U.S. population, including about 50% of all people over age 60, have hypertension, but that only about one third of these are aware of their condition and are under appropriate treatment. People who have normal blood pressure at age 55 still have a 90% lifetime risk of becoming hypertensive. The treatment of this disorder and its complications in the U.S. is estimated to cost $37 billion annually. Hypertension causes 35,000 deaths each year in the U.S., and is a contributing factor in a further 180,000 deaths. It is associated with a threefold increase in the risk of heart attack and a seven to tenfold increase in the risk of stroke. The prevalence of hypertension and the incidence of nonfatal and fatal consequences are substantially higher in African-Americans. Essential hypertension is currently recognized as a group of syndromes, induced by a complex interaction of genetic and environmental factors, which may also include obesity, abnormal glucose and lipid metabolism, insulin resistance, diminished arterial compliance, accelerated atherogenesis, and renal disease. Some features of the hypertensive diathesis (left ventricular hypertrophy, decreased arterial compliance) may occur even before blood pressure measurements detect significant elevation. Although people with extremely high diastolic pressure may experience headache, dizziness, and even encephalopathy, uncomplicated hypertension seldom causes symptoms. Hence the diagnosis of hypertension is usually made by screening apparently healthy people or those under treatment for another condition. Risk factors for hypertension include a family history of the condition, African-American race, advancing age, the postmenopausal state, obesity, obstructive sleep apnea, excessive use of alcohol, sedentary lifestyle, and chronic emotional stress. Treatment options include lifestyle changes (maintenance of healthful weight; a diet low in saturated and total fat and rich in fruits, vegetables, and low-fat dairy products; at least 30 minutes of aerobic exercise several days a week; limitation of sodium intake to 2.4 g daily and of ethanol to 1 oz daily; consumption of adequate potassium, calcium, and magnesium; and avoidance of excessive emotional stress) and a broad range of drugs, including diuretics, beta-blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, )-1 adrenergic antagonists, centrally acting )-agonists, and others. One large study found a thiazide diuretic superior to a calcium channel blocker and an ACE inhibitor in reducing cardiovascular mortality in people with hypertension and one additional cardiovascular risk factor. In recent decades, early detection and aggressive treatment of hypertension have reduced associated morbidity and mortality. Control of hypertension lowers the risk of stroke by 30–50%. Current practice standards call for diligent efforts at prevention through avoidance of known risk factors, particularly in people with a family history of hypertension, and control of cofactors known to increase the risk of cardiovascular damage in people with hypertension (smoking, hypercholesterolemia, diabetes mellitus). Some studies suggest that the goal of treatment should be a diastolic blood pressure of 80 mmHg or lower.


Reference: Stedman's Medical Dictionary


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