Ophthalmology => High Blood Pressure
High Blood Pressure
Hypertension or High Blood Pressure, physiological condition involving increased pressure on the arterial walls. Generally both the systolic and diastolic pressure are elevated, although diastolic pressure only may be increased. Many persons have a condition known as labile hypertension, in which blood pressure is elevated on initial examination but registers normal on subsequent measurements. For this reason a diagnosis of true, or sustained, hypertension requires elevated blood pressure readings on several occasions.
Elevated arterial blood pressure indicates increased arterial resistance to blood flow ,but in 90 percent of patients no cause for this increased resistance can be identified. These cases are called primary, or essential, hypertension. Secondary hypertension can be the outcome of toxemia, of pregnancy, vascular or kidney diseases, or endocrine tumors.
The average age of onset of essential hypertension is about 35. Some degree of hypertension is present in about one in six American adults and is more common in blacks than in whites. Most persons with hypertension have no symptoms. For this reason large-scale screening programs have been instituted to detect people with elevated blood pressure, for if left untreated, hypertension increases the risk of death from heart attack and produces damage to the kidneys, nervous system, and especially the eyes. When found early and treated, the effects of this condition can be greatly reduced. Blood pressure can vary greatly with circumstances or time of day, or with patient's age, so undue significance should not be placed upon a single reading.
Several types of drugs have proved useful for severe hypertension. Diuretics promote salt and water excretion, reducing the work the heart must do to pump blood through the kidneys; vasodilators, renin inhibitors, and calcium antagonists reduce the resistance to blood flow in arteries; and ganglionic blockers and beta-adrenergic blockers help to control heartbeat and arterial tone. Therapy also includes a low-salt diet and an attempt to reduce the emotional stress of the patient's life. Drug treatment for mild hypertension is debated, because the drugs can have side effects that exceed their usefulness.
The widespread detection and treatment of hypertension in Western countries has been credited with contributing to the dramatic fall in death from heart disease that occurred during the 1970s and '80s.