Hypertension

History

Complications

Causes and symptoms

Diagnosis

Treatment

Prognosis

Prevention

Resources

Hypertension is high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries as it flows through them. Arteries are the blood vessels that carry oxygenated blood from the heart to the body’s tissues. According to the U.S. Centers for Disease Control and Prevention (CDC), in 2004, hypertension killed over 2,900 people in the United States; which relates to about 7.8 people per 100,000 in the U.S. population.

As blood flows through arteries it pushes against the inside of the artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure will be. The size of small arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls narrow, or constrict.

Blood pressure is highest when the heart beats to push blood out into the arteries. When the heart relaxes to fill with blood again, the pressure is at its lowest point. Blood pressure when the heart beats is called systolic pressure. Blood pressure when the heart is at rest is called diastolic pressure. When blood pressure is measured, the systolic pressure is stated first and the diastolic pressure second. Blood pressure is measured

in millimeters of mercury (mm Hg). For example, if a person’s systolic pressure is 120 and diastolic pressure is 80, it is written as 120/80 mm Hg. The American Heart Association considers blood pressure less than 140 over 90 normal for adults.

Hypertension is a major health problem, especially because it has no symptoms. Many people have hypertension without knowing it. In the United States, about 50 million people age six years and older have high blood pressure. Hypertension is more common in men than women and in people over the age of 65 years than in younger persons. More than half of all Americans over the age of 65 years have hypertension. It is also more common in African-Americans than in white Americans.

History

Attempts to find effective ways to treat hypertension led researchers to uncover the methods by which the body regulates blood pressure; knowledge of that process is still evolving. In 1898, physiologists Robert Adolf Tigerstedt (1853–1923) and Per Gustaf Bergman (1874–1955) found that an enzyme produced by the kidneys affected blood pressure. American pathologist Henry Goldblatt (1891–1977) and colleagues confirmed the role of the kidneys in 1934, producing hypertension in dogs by constricting the kidney arteries. In 1940, Braun-Menendez in Argentina and Irvine Page and Oscar Helmer at the Cleveland Clinic in Ohio found that renin, the kidney enzyme, catalyzed the formation of angiotensin, a very potent vasoconstrictor (a substance that causes blood vessels to contract). In the 1950s, researchers discovered that renin causes the production of angiotensin I, which has little physiological effect but is stimulated by angiotensin converting enzyme to produce the vessel-constricting angiotensin II. In the 1960s, F. Gross and others further found that angiotensin stimulates production of the hormone aldosterone by the adrenal glands, which in turn promotes retention of sodium and water, boosting the fluid content of the circulatory system and, thus, the pressure on blood vessel walls. Angiotensins were also shown to act on the nervous system, stimulating release of the neurotransmitter norepinephrine, which signals the arterioles to constrict. This complex is called the reninangiotensin-aldosterone system. Exactly why the system malfunctions to produce hypertension is not yet known, except in the approximately 10% of cases in which high blood pressure is the result of specific, known physical disorders, particularly of the kidneys and adrenal glands.

Effective drug treatments to control high blood pressure were not developed until after World War II (1939–1945), although some early attempts at drug treatment were made. French surgeon Mathieu Jaboulay (1860–1913), in 1900, reported on his drastic approach to alleviate severe hypertension: sympathectomy, or the cutting of the nerves that stimulate blood vessel constriction. Two American doctors took a dietary approach; Frederick Allen promoted salt and water restriction in 1920, and Walter Kempner (1903–1997) put patients on a no-salt rice diet in the 1940s.

The modern era of drug treatment for hypertension began with the introduction of reserpine in 1953. Reserpine was first derived from the snakeroot plant, Rauwolfia serpentina, long used by medical practitioners in India, both to lower blood pressure and induce relaxation. Rauwolfia was first mentioned in Western medical literature in a 1563 Portuguese work, but it was not studied seriously by Western-trained Indian physicians until 1931. The results of a clinical trial published by Dr. Rustom Jal Vakil (1911–1974) in 1949 caught the attention of Dr. Robert Wilkins, director of the hypertension clinic at Massachusetts General Hospital. Wilkins confirmed the hypotensive (anti-hypertensive) effect of Rauwolfia in 1952. The active ingredient was soon isolated and named reserpine; it was synthesized in 1956 by Robert Burns Woodward of Harvard University (Massachusetts). Reserpine was the first antihyperten-sive drug to achieve wide clinical use because of its nearly universal effectiveness. (It acts by interfering with transmission of norepinephrine.) It was also widely sold as a tranquilizer.

Other drugs took the place of reserpine as manufacturers and researchers focused their attention on anti-hypertensives beginning in the 1950s. The discovery of the first thiazide diuretic, benzothiadiazine, was reported in 1957 by the drug company Merck, Sharp and Dohme. Thiazide diuretics, which increase excretion of sodium chloride and water by stimulating the flow of urine, are widely used today to lower blood pressure. They may be taken in combination with methyldopa, an antihypertensive introduced in 1963, or with the beta-blockers, a new class of drugs that came on the market in 1964. James Black, senior pharmacologist at Imperial Chemical Industries of Great Britain, was responsible for the development of the first beta blocker, propranolol. American biochemist Raymond Ahlquist had suggested that epinephrine and norepinephrine transmit their signals—which cause an increase in heart rate and stronger contractions of the heart and blood vessels—to beta receptor sites on the heart muscle. In 1957, Black noted reports of a drug that blocked the stimulating effects of adrenaline on the heart, and set about creating a new chemical compound that would block the effects of epinephrine and norepinephrine at the beta receptor sites. This was accomplished by 1960, with the improved beta-blocker propranolol appearing in 1964. Beta blockers are now widely used to treat both angina and high blood pressure.

Two other antihypertensives were introduced in the 1980s. Calcium channel blockers work by blocking the channel that carries calcium to muscle cells; since calcium is required for contraction of the muscles in artery walls and affects the rate at which the heart beats, lowering calcium levels in muscle also lowers blood pressure. ACE (angiotensin converting enzyme) inhibitors interfere with the effect of an enzyme that stimulates angiotensin I to convert to the powerful vasoconstrictor angiotensin II and that also promotes the destruction of bradykinin, a powerful vasodilator (a substance that promotes the relaxation of blood vessels). Ferreira and his coworkers first found BPFs, factors that intensify the body’s reaction to bradykinin, in the venom of pit vipers in the 1960s. The BPFs inhibited the action of an enzyme that Erdos and associates showed was identical to angiotensin converting enzyme. BPFs were then synthesized, and in 1977 Cushman and his colleagues developed the first orally effective ACE inhibitor, captopril. Recently, it has been discovered that ACE inhibitors also reduce the rate of heart failure and progress of heart disease following heart attack.

Other drug treatments include sympathetic (adrenergic) nervous system blockers, which inhibit the sympathetic nervous system; vasodilators, which lower vascular resistance by dilating the blood vessels; and HMG-CoA reductase inhibitors, which are used with dietary modifications to reduce cholesterol levels. However, drug therapy, which usually includes side effects, is not the only way to treat hypertension. From the 1970s on, doctors have recommended exercise, weight loss, eliminating smoking, stress reduction, and a diet low in sodium, caffeine, alcohol, and cholesterol as a means of lowering blood pressure.

Advances are also being made in discovering the biological roots of hypertension. For example, in 1998 researchers reported that glucocorticoid (a specific group of corticoids, or adrenal cortex steroids) abnormalities may play a role in familial disposition to hypertension. Investigators also identified two oncogenes that may be related to sodium-related hypertension by affecting how sodium is released or retained by sodium channels in the kidneys. Variations of an ACE (angiotensin converting enzyme) gene, which encodes for an enzyme that helps regulate blood volume and controls salt and water balance, have also been linked to hypertension in men but not women.

Complications

Hypertension is serious because people with the condition have a higher risk for heart disease and other medical problems than people with normal blood pressure. Serious complications can be avoided by getting regular blood pressure checks and treating hypertension as soon as it is diagnosed.

If left untreated, hypertension can lead to the following medical conditions:

• Arteriosclerosis, also called atherosclerosis,
• Heart attack,
• Stroke,
• Enlarged heart, and
• Kidney damage.

Arteriosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as blood flows through them. High blood pressure can make the artery walls thicken and harden. When artery walls thicken, the inside of the blood vessel narrows. Cholesterol and fats are more likely to build up on the walls of damaged arteries, making them even narrower. Blood clots can also get trapped in narrowed arteries, blocking the flow of blood.

Arteries narrowed by arteriosclerosis may not deliver enough blood to organs and other tissues. Reduced or blocked blood flow to the heart can cause a heart attack. If an artery to the brain is blocked, a stroke can result.

Hypertension makes the heart work harder to pump blood through the body. The extra workload can make the heart muscle thicken and stretch. When the heart becomes too enlarged it cannot pump enough blood. If the hypertension is not treated, the heart may fail.

The kidneys remove the body’s wastes from the blood. If hypertension thickens the arteries to the kidneys, less waste can be filtered from the blood. As the condition worsens, the kidneys fail and wastes build up in the blood. Dialysis or a kidney transplant are needed when the kidneys fail. About 25% of people who receive kidney dialysis have kidney failure caused by hypertension.

Causes and symptoms

Many different actions or situations can normally raise blood pressure. Physical activity can temporarily raise blood pressure. Stressful situations can make blood pressure go up. When the stress goes away, blood pressure usually returns to normal. These temporary increases in blood pressure are not considered hypertension. A diagnosis of hypertension made only when a person has multiple high blood pressure readings over a period of time.

The cause of hypertension is not known in 90 to 95% of the people who have it. Hypertension without a known cause is called primary or essential hypertension.

When a person has hypertension caused by another medical condition, it is called secondary hypertension. Secondary hypertension can be caused by a number of different illnesses. Many people with kidney disorders have secondary hypertension. The kidneys regulate the balance of salt and water in the body. If the kidneys cannot rid the body of excess salt and water, blood pressure goes up. Kidney infections, a narrowing of the arteries that carry blood to the kidneys, called renal artery stenosis, and other kidney disorders can disturb the salt and water balance.

Cushing syndrome and tumors of the pituitary and adrenal glands often increase levels of the adrenal gland hormones cortisol, adrenalin, and aldosterone, which can cause hypertension. Other conditions that can cause hypertension are blood vessel diseases, thyroid gland disorders, some prescribed drugs, alcoholism, and pregnancy.

Even though the cause of most hypertension is not known, some people have risk factors that give them a greater chance of getting hypertension. Many of these risk factors can be changed to lower the chance of developing hypertension or as part of a treatment program to lower blood pressure.

Risk factors for hypertension include:

• Age over 60 years,
• Male gender,
• Race,
• Heredity,
• Salt sensitivity,
• Obesity,
• Inactive lifestyle,
• Heavy alcohol consumption, and
• Use of oral contraceptives.

Some risk factors for getting hypertension can be changed, while others cannot. Age, male gender, and race are risk factors that a person cannot do anything about. Some people inherit a tendency to get hypertension. People with family members who have hypertension are more likely to develop it than those whose relatives are not hypertensive. A person with these risk factors can avoid or eliminate the other risk factors to lower their chance of developing hypertension.

Diagnosis

Because hypertension does not cause symptoms, it is important to have blood pressure checked regularly. Blood pressure is measured with an instrument called a sphygmomanometer. A cloth-covered rubber cuff is wrapped around the upper arm and inflated. When the cuff is inflated, an artery in the arm is squeezed to momentarily stop the flow of blood. Then, the air is let out of the cuff while a stethoscope placed over the artery is used to detect the sound of the blood spurting back through the artery. This first sound is the systolic pressure, the pressure when the heart beats. The last sound heard as the rest of the air is released is the diastolic pressure, the pressure between heart beats. Both sounds are recorded on the mercury gauge on the sphygmomanometer.

Normal blood pressure is defined by a range of values. Blood pressure lower than 140/90 mm Hg is considered normal. A blood pressure around 120/80 mm Hg is considered the best level to avoid heart disease. A number of factors such as pain, stress, or anxiety can cause a temporary increase in blood pressure. For this reason, hypertension is not diagnosed on one high blood pressure reading. If a blood pressure reading is 140/90 or higher for the first time, the physician will have the person return for another blood pressure check. Diagnosis of hypertension usually is made based on two or more readings after the first visit.

Systolic hypertension of the elderly is common and is diagnosed when the diastolic pressure is normal or low, but the systolic is elevated, e.g., 170/70 mm Hg. This condition usually co-exists with hardening of the arteries (atherosclerosis).

Blood pressure measurements are classified in stages, according to severity:

• Normal blood pressure: less than 130/85 mm Hg,
• High normal: 130 to 139/85 to 89 mm Hg,
• Mild hypertension: 140 to 159/90 to 99 mm Hg,
• Moderate hypertension: 160 to 179/100 to 109 mm Hg,
• Severe hypertension: 180 to 209/110 to 119, and
• Very severe hypertension: 210/120 or higher.

A typical physical examination to evaluate hypertension includes:

• Medical and family history,
• Physical examination,
• Ophthalmoscopy: Examination of the blood vessels in the eye,
• Chest x-ray,
• Electrocardiograph (ECG), and
• Blood and urine tests.

The medical and family history help the physician determine if the patient has any conditions or disorders that might contribute to or cause the hypertension. A family history of hypertension might suggest a genetic predisposition for hypertension.

The physical examination may include several blood pressure readings at different times and in different positions. The physician uses a stethoscope to listen to sounds made by the heart and blood flowing through the arteries. The pulse, reflexes, height, and weight are checked and recorded. Internal organs are palpated, or felt, to determine if they are enlarged.

Because hypertension can cause damage to the blood vessels in the eyes, the eyes may be checked with a instrument called an ophthalmoscope. The physician will look for thickening, narrowing, or hemorrhages in the blood vessels.

A chest x ray can detect an enlarged heart, other vascular (heart) abnormalities, or lung disease.

An electrocardiogram (ECG) measures the electrical activity of the heart. It can detect if the heart muscle is enlarged and if there is damage to the heart muscle from blocked arteries.

Urine and blood tests may be done to evaluate health and to detect the presence of disorders that might cause hypertension.

Treatment

There is no cure for primary hypertension, but blood pressure can almost always be lowered with the correct treatment. The goal of treatment is to lower blood pressure to levels that will prevent heart disease and other complications of hypertension. In secondary hypertension, the disease that is responsible for the hypertension is treated in addition to the hypertension itself. Successful treatment of the underlying disorder may cure the secondary hypertension.

Treatment to lower blood pressure usually includes changes in diet, getting regular exercise, and taking antihypertensive medications. Patients with mild or moderate hypertension who do not have damage to the heart or kidneys may first be treated with lifestyle changes.

Lifestyle changes that may reduce blood pressure by about 5 to 10 mm Hg include:

• Reducing salt intake,
• Reducing fat intake,
• Losing weight,
• Getting regular exercise,
• Quitting smoking,
• Reducing alcohol consumption, and
• Managing stress.

Patients whose blood pressure remains higher than 139/90 will most likely be advised to take antihypertensive medication. Numerous drugs have been developed to treat hypertension. The choice of medication will depend on the stage of hypertension, side effects, other medical conditions the patient may have, and other medicines the patient is taking.

Patients with mild or moderate hypertension are initially treated with monotherapy, a single antihypertensive medicine. If treatment with a single medicine fails to lower blood pressure enough, a different medicine may be tried or another medicine may be added to the first. Patients with more severe hypertension may initially be given a combination of medicines to control their hypertension. Combining antihypertensive medicines with different types of action often controls blood pressure with smaller doses of each drug than would be needed for monotherapy.

Antihypertensive medicines fall into several classes of drugs:

• Diuretics,
• Beta-blockers,
• Calcium channel blockers,
• Angiotensin converting enzyme inhibitors (ACE inhibitors),
• Alpha-blockers,
• Alpha-beta blockers,
• Vasodilators,
• Peripheral acting adrenergic antagonists, and
• Centrally acting agonists.

Diuretics help the kidneys eliminate excess salt and water from the body’s tissues and the blood. This helps reduce the swelling caused by fluid buildup in the tissues. The reduction of fluid dilates the walls of arteries and lowers blood pressure.

Beta-blockers lower blood pressure by acting on the nervous system to slow the heart rate and reduce the force of the heart’s contraction. They are used with caution in patients with heart failure, asthma, diabetes, or circulation problems in the hands and feet.

Calcium channel blockers block the entry of calcium into muscle cells in artery walls. Muscle cells need calcium to constrict, so reducing their calcium keeps them more relaxed and lowers blood pressure.

ACE inhibitors block the production of substances that constrict blood vessels. They also help reduce the build-up of water and salt in the tissues. They are often given to patients with heart failure, kidney disease, or diabetes. ACE inhibitors may be used together with diuretics.

Alpha-blockers act on the nervous system to dilate arteries and reduce the force of the heart’s contractions.

Alpha-beta blockers combine the actions of alpha and beta blockers.

Vasodilators act directly on arteries to relax their walls so blood can move more easily through them. They lower blood pressure rapidly and are injected in hypertensive emergencies when patients have dangerously high blood pressure.

Peripheral acting adrenergic antagonists act on the nervous system to relax arteries and reduce the force of the heart’s contractions. They usually are prescribed together with a diuretic. Peripheral acting adrenergic antagonists can cause slowed mental function and lethargy.

Centrally acting agonists also act on the nervous system to relax arteries and slow the heart rate. They are usually used with other antihypertensive medicines.

KEY TERMS

Arteries —Blood vessels that carry blood to organs and other tissues of the body.

Arteriosclerosis —Hardening and thickening of artery walls.

Cushing syndrome —A disorder in which too much of the adrenal hormone, cortisol, is produced; it may be caused by a pituitary or adrenal gland tumor.

Diastolic blood pressure —Blood pressure when the heart is resting between beats.

Hypertension —High blood pressure.

Renal artery stenosis —Disorder in which the arteries that supply blood to the kidneys constrict.

Sphygmomanometer —An instrument used to measure blood pressure.

Systolic blood pressure —Blood pressure when the heart contracts (beats).

Vasodilator —Any drug that relaxes blood vessel walls.

Ventricles —The two lower chambers of the heart; also the main pumping chambers.

Prognosis

There is no cure for hypertension. However, it can be well controlled with the proper treatment. Therapy with a combination of lifestyle changes and antihypertensive medicines usually can keep blood pressure at levels that will not cause damage to the heart or other organs. The key to avoiding serious complications of hypertension is to detect and treat it before damage occurs. Because antihypertensive medicines control blood pressure, but do not cure it, patients must continue taking the medications to maintain reduced blood pressure levels and avoid complications.

Prevention

Prevention of hypertension centers on avoiding or eliminating known risk factors. Even persons at risk because of age, race, or sex or those who have an inherited risk can lower their chance of developing hypertension.

The risk of developing hypertension can be reduced by making the same changes recommended for treating hypertension.

Resources

BOOKS

Fuster, Valentin, ed. Hurst’s The Heart. New York: McGraw-Hill, Medical Publications Division, 2004.

Rosendorff, Clive, ed. Essential Cardiology: Principles and Practice. Totowa, NJ: Humana Press, 2005.

Zipes, Douglas, ed. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia, PA: W.B. Saunders, 2005.

Toni Rizzo

Hypertension

Definition

Hypertension is the medical term for high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries as it flows through them. Arteries are the blood vessels that carry oxygenated blood from the heart to the body's tissues.

Description

As blood flows through arteries, it pushes against the inside of the artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure. The size of small arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls are narrow, or constricted.

Blood pressure is highest when the heart beats to pump blood out into the arteries. When the heart relaxes to fill with blood again, the pressure is at its lowest point. Blood pressure when the heart beats is called systolic pressure. Blood pressure when the heart is at rest is called diastolic pressure. When blood pressure is measured, the systolic pressure is stated first and the diastolic pressure second. Blood pressure is measured in millimeters of mercury (mm Hg). For example, if a person's systolic pressure is 120 and diastolic pressure is 80, it is written as 120/80 mm Hg. The American Heart Association considers blood pressure above 140 over 90 high for adults.

Hypertension is a major health problem, especially because it has no symptoms. Many people have hypertension without knowing it. In the United States, about 50 million people age sixty and older have high blood pressure. Hypertension is more common in men than women and in people over the age of 65 than in younger persons. More than half of all Americans over the age of 65 have hypertension. It is also more common in African-Americans than in white Americans.

Hypertension is serious because people with the condition have a higher risk for heart disease and other medical problems than people with normal blood pressure. Serious complications can be avoided by getting regular blood pressure checks and treating hypertension as soon as it is diagnosed.

If left untreated, hypertension can lead to the following medical conditions:

• arteriosclerosis, also called atherosclerosis
• blindness
• heart attack
• stroke
• enlarged heart
• kidney damage

Arteriosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as blood flows through them. High blood pressure can make the artery walls thicken and harden. When artery walls thicken, the inside of the blood vessel narrows. Cholesterol and fats are more likely to build up on the walls of damaged arteries, making them even narrower. Blood clots can also get trapped in narrowed arteries, blocking the flow of blood.

Arteries narrowed by arteriosclerosis may not deliver enough blood to organs and other tissues. Reduced or blocked blood flow to the heart can cause a heart attack. If an artery to the brain is blocked, a stroke can result.

Hypertension makes the heart work harder to pump blood through the body. The extra workload can make the heart muscle thicken and stretch. When the heart becomes too enlarged it cannot pump enough blood. If the hypertension is not treated, the heart may fail.

The kidneys remove the body's wastes from the blood. If hypertension thickens the arteries to the kidneys, less waste can be filtered from the blood. As the condition worsens, the kidneys fail and wastes build up in the blood. Dialysis or a kidney transplant are needed when the kidneys fail. About 25% of people who receive kidney dialysis have kidney failure caused by hypertension.

Causes & symptoms

Many different actions or situations can normally raise blood pressure. Physical activity can temporarily raise blood pressure. Stressful situations can make blood pressure go up. When the stress goes away, blood pressure usually returns to normal. These temporary increases in blood pressure are not considered hypertension. A diagnosis of hypertension is made only when a person has multiple high blood pressure readings over a period of time.

The cause of hypertension is not known in 90–95% of the people who have it. Hypertension without a known cause is called primary or essential hypertension. When a person has hypertension caused by another medical condition, it is called secondary hypertension. Secondary hypertension can be caused by a number of different illnesses. Many people with kidney disorders have secondary hypertension. The kidneys regulate the balance of salt and water in the body. If the kidneys cannot rid the body of excess salt and water, blood pressure goes up. Kidney infections , a narrowing of the arteries that carry blood to the kidneys, called renal artery stenosis, and other kidney disorders can disturb the salt and water balance.

Cushing's syndrome and tumors of the pituitary and adrenal glands often increase levels of the adrenal gland hormones cortisol, adrenalin, and aldosterone, which can cause hypertension. Other conditions that can cause hypertension are blood vessel diseases, thyroid gland disorders, some prescribed drugs, alcoholism , and pregnancy .

Even though the cause of most hypertension is not known, some people have risk factors that give them a greater chance of getting hypertension. Many of these risk factors can be changed to lower the chance of developing hypertension or as part of a treatment program to lower blood pressure.

Risk factors for hypertension include:

• age over 60
• male sex
• race (The African-American community has a higher incidence of hypertension.)
• heredity

• salt sensitivity
• obesity
• inactive lifestyle
• heavy alcohol consumption
• use of oral contraceptives

Some risk factors for hypertension can be changed, while others cannot. Age, male sex, and race are risk factors that a person cannot deter. Some people inherit a tendency to get hypertension. People with family members who have hypertension are more likely to develop it than those whose relatives are not hypertensive. People with these risk factors can avoid or eliminate the other risk factors to lower their chance of developing hypertension.

Diagnosis

Because hypertension does not cause symptoms, it is important to have blood pressure checked regularly. Blood pressure is measured with an instrument called a sphygmomanometer. A cloth-covered rubber cuff is wrapped around the upper arm and inflated. When the cuff is inflated, an artery in the arm is squeezed to momentarily stop the flow of blood. Then, the air is let out of the cuff while a stethoscope placed over the artery is used to detect the sound of the blood spurting back through the artery. This first sound is the systolic pressure, the pressure when the heart beats. The last sound heard as the rest of the air is released is the diastolic pressure, the pressure between heartbeats. Both sounds are recorded on the mercury gauge on the sphygmomanometer.

A number of such factors as pain , stress, or anxiety can cause a temporary increase in blood pressure. For this reason, hypertension is not diagnosed on the basis of only one high blood pressure reading. If a blood pressure reading is 140/90 or higher for the first time, the physician will have the person return for another blood pressure check. Diagnosis of hypertension usually is made based on two or more readings after the first visit. Sometimes, patients have high blood pressure only while in the doctor's office. This phenomenon, called "white-coat hypertension" has usually been dismissed as mere anxiety over visiting the doctor. In late 2001, an Italian study questioned dismissal of these patients as not being hypertensive and encouraged further study.

Systolic hypertension of the elderly is common and is diagnosed when the diastolic pressure is normal or low, but the systolic is elevated, e.g. 170/70 mm Hg. This condition usually coexists with hardening of the arteries (atherosclerosis).

Blood pressure measurements are classified in stages according to severity:

• normal blood pressure: lower than 130/85 mm Hg
• high normal: 130–139/85–89 mm Hg
• mild hypertension: 140–159/90–99 mm Hg
• moderate hypertension: 160–179/100–109 mm Hg
• severe hypertension: 180–209/110–119
• very severe hypertension: 210/120 or higher

A typical physical examination to evaluate hypertension includes:

• medical and family history
• physical examination
• ophthalmoscopy: examination of the blood vessels in the eye
• chest x ray
• electrocardiograph (ECG)
• blood and urine tests

The medical and family history help the physician determine if the patient has any conditions or disorders that might contribute to or cause the hypertension. A family history of hypertension might suggest a genetic predisposition to the disorder.

The physical exam may include several blood pressure readings at different times and in different positions. The physician uses a stethoscope to listen to sounds made by the heart and blood flowing through the arteries. The pulse, reflexes, height, and weight are checked and recorded. Internal organs are palpated, or felt, to determine if they are enlarged.

Because hypertension can cause damage to the blood vessels in the eyes, the eyes may be checked with an instrument called an ophthalmoscope. The physician will look for thickening, narrowing, or hemorrhages in the blood vessels.

A chest x ray can detect an enlarged heart, other heart abnormalities, or lung disease.

An electrocardiogram (ECG) measures the electrical activity of the heart. It can detect if the heart muscle is enlarged and if there is damage to the heart muscle from blocked arteries.

Urine and blood tests may be done to further evaluate health and to detect the presence of disorders that might cause hypertension.

Treatment

There is no cure for primary hypertension, but blood pressure can almost always be lowered with the correct treatment. The goal of treatment is to lower blood pressure to levels that will prevent heart disease and other complications of hypertension. In secondary hypertension, the disease that is responsible for the hypertension is treated in addition to the hypertension itself. Successful treatment of the underlying disorder may cure the secondary hypertension.

Treatment to lower blood pressure usually includes changes in diet and getting regular exercise . Patients with mild or moderate hypertension who do not have damage to the heart or kidneys may first be treated primarily with lifestyle changes.

Lifestyle changes that may reduce blood pressure by about 5–10 mm Hg include:

• reducing salt intake
• reducing fat intake
• losing weight
• getting regular exercise
• quitting smoking
• reducing alcohol consumption
• managing stress

Natural remedies approved by a physician may also lower or even prevent hypertension. Aromatherapy as a treatment option uses essential oils either inhaled from a bottle in times of anxiety or massaged daily into the skin at bedtime in the area beneath the collarbone. Blue chamomile and lavender are known for their stress relief and relaxation effects.

Food therapy has also been shown to affect blood pressure. Muscles that regulate blood pressure have been noted to dilate with the intake of celery; celery juice has also been found to have a mild diuretic effect. Eating fresh fruits and vegetables, which are high in potassium and magnesium , lowers systemic sodium and fluid levels in the circulatory system. A 2001 study showed that reducing intake of sodium decreases blood pressure in participants with or without hypertension. Garlic intake has also been linked with lowering blood pressures. Taken either via enteric-coated capsules or fresh garlic cloves, allicin is thought to be the ingredient that brings down the blood pressure.

Relaxation and meditation can help lower blood pressure. Focusing on relaxing music can also slow the heart rate and lower blood pressure, as can imagery (envisioning coolness seeping into the pores and throughout the body, sensing that blood pressure is within normal range). Yoga experts cite two specific poses, the corpse pose and the knee squeeze, when used in combination with breathing exercises, as being particularly helpful in relieving tension and improving blood flow.

Allopathic treatment

Patients whose blood pressure remains higher than 139/90 will most likely be advised to take antihypertensive medication. Numerous drugs have been developed to treat hypertension. The choice of medication will depend on the stage of hypertension, side effects, other medical conditions the patient may have, and other medicines the patient is taking.

Patients with mild or moderate hypertension are initially treated with monotherapy, a single antihypertensive medicine. If treatment with a single medicine fails to lower blood pressure sufficiently, a different medicine may be tried or another medicine may be added to the first. Patients with more severe hypertension may initially be given a combination of medicines to control their hypertension. Combining antihypertensive medicines with different types of action often controls blood pressure with smaller doses of each drug than would be needed for monotherapy.

Antihypertensive medicines fall into several classes:

• diuretics
• beta-blockers
• calcium channel blockers
• angiotensin-converting enzyme inhibitors (ACE inhibitors)
• alpha-blockers
• alpha-beta blockers
• vasodilators
• peripheral-acting adrenergic antagonists
• centrally-acting agonists

Diuretics help the kidneys eliminate excess salt and water from the body's tissues and the blood. This helps reduce the swelling caused by fluid buildup in the tissues. The reduction of fluid dilates the walls of arteries and lowers blood pressure.

Beta-blockers lower blood pressure by acting on the nervous system to slow the heart rate and reduce the force of the heart's contraction. They are used with caution in patients with heart failure, asthma , diabetes, or circulation problems in the hands and feet.

Calcium channel blockers block the entry of calcium into muscle cells in artery walls. Muscle cells need calcium to constrict, so reducing their calcium keeps them more relaxed and lowers blood pressure.

ACE inhibitors block the production of substances that constrict blood vessels. They also help reduce the buildup of water and salt in the tissues. They are often given to patients with heart failure, kidney disease, or diabetes. ACE inhibitors may be used together with diuretics.

Alpha-blockers act on the nervous system to dilate arteries and reduce the force of the heart's contractions.

Alpha-beta blockers combine the actions of alpha and beta blockers.

Vasodilators act directly on arteries to relax their walls so blood can move more easily through them. They lower blood pressure rapidly and are injected in hypertensive emergencies when patients have dangerously high blood pressure.

Peripheral-acting adrenergic antagonists act on the nervous system to relax arteries and reduce the force of the heart's contractions. They usually are prescribed together with a diuretic. Peripheral acting adrenergic antagonists can cause slowed mental function and lethargy.

Centrally-acting agonists also act on the nervous system to relax arteries and slow the heart rate. They are usually used with other antihypertensive medicines.

In 2001, a medical device company announced findings about the effectiveness of a breathing device to work along with antihypertensive medications. By helping patients alter breathing patterns to lengthen the phase in which they exhale, they could slow breathing and see beneficial effects on blood pressure accumulate. The device is available through prescription only, but is pending over-the-counter-clearance from the Food and Drug Administration (FDA.)

Expected results

There is no cure for hypertension. However, it can be well controlled with the proper treatment. The key to avoiding serious complications of hypertension is to detect and treat it before damage occurs. Because antihypertensive medicines control blood pressure, but do not cure it, patients must continue taking the medications to maintain reduced blood pressure levels and avoid complications.

Prevention

Prevention of hypertension centers on avoiding or eliminating known risk factors. Even persons at risk because of age, race, or sex or those who have an inherited risk can lower their chance of developing hypertension.

The risk of developing hypertension can be reduced by making the same lifestyle changes recommended for treating hypertension.

Resources

BOOK

Bellenir, Karen, and Peter D. Dresser, eds. Cardiovascular Diseases and Disorders Sourcebook. Detroit: Omnigraphics, 1995.

Texas Heart Institute. Heart Owner's Handbook. New York: John Wiley and Sons, 1996.

PERIODICALS

Boschart, Sherry. "Guided Breathing Exercise May Help Cut Hypertension (Preliminary Trial Results)." Internal Medicine News 34, no. 21 (November 1, 2001): 30–31.

"Study Suggests White-Coat Hypertension is Not Harmless." Medical Devices and Surgical Technology Week (December 23, 2001): 26.

Vollmer, William M., et al. "Effects of Diet and Sodium Intake on Blood Pressure: Subgroup Analysis of the DASH-Sodium Trail." Annals of Internal Medicine 135, no. 12 (December 18, 2001): 1019–1020.

ORGANIZATION

American Heart Association. 7272 Greenview Avenue, Dallas, TX 75231-4596. (800) AHS-USA1. <http://www.amhrt.org>.

National Heart, Lung, and Blood Institute. Information Center. PO Box 30105, Bethesda, MD 20824-0105. (301) 251-1222.

Texas Heart Institute. Heart Information Service, PO Box 20345, Houston, TX 77225-0345. (800) 292-2221.

Kathleen Wright

Teresa G. Odle

Hypertension

Definition

Hypertension is high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries. Arteries are the blood vessels that carry oxygenated blood from the heart to the body's tissues.

Description

As blood flows through arteries, it pushes against the inside of artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure is. The size of arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls narrow, or constricted.

Blood pressure is highest when the heart beats to push blood out into the arteries. When the heart relaxes to fill with blood again, the pressure is at its lowest point. Blood pressure when the heart beats is called systolic pressure. Blood pressure when the heart is at rest is called diastolic pressure. When blood pressure is measured, the systolic pressure is stated first and the diastolic pressure second. Blood pressure is measured in millimeters of mercury (mm Hg). For example, if a person's systolic pressure is 120 and diastolic pressure is 80, it is written as 120/80 mm Hg.

Blood pressure measurements

The National Heart, Lung, and Blood Institute in Bethesda, Maryland released clinical guidelines for blood pressure in 2003, lowering the standard normal readings for adults to less than 120 over less than 80.

Although there are set blood pressure ranges for adults, normal blood pressure ranges for children vary according to age, gender, and height so that different levels of growth are considered when evaluating blood pressure. In children, blood pressure normally rises during growth and maturation and varies greatly during adolescence .

Specific systolic and diastolic blood pressure percentiles have been established for each age, gender, and height group. In children ages six to 12, up to 125/80 mm Hg is considered normal. In youth ages 12–15, 126/78 mm Hg is normal, and for ages 16–18, 132/82 mm Hg is normal.

Children whose blood pressure is above the 95th percentile for their age/gender/height group are diagnosed with hypertension. Children whose blood pressure is between the 90th and 95th percentile are diagnosed with pre-hypertension. Adolescents whose blood pressure is greater than 120/80 also may be diagnosed with pre-hypertension.

Complications

Childhood hypertension is serious because it increases the risk of heart disease, stroke , and other medical problems in adulthood. Serious complications can be avoided by ensuring the child gets regular blood pressure checks and by treating hypertension as soon as it is diagnosed.

If left untreated, hypertension can lead to the following long-term complications:

• atherosclerosis, also called arteriosclerosis
• peripheral vascular disease
• heart attack
• stroke
• enlarged heart and heart failure
• kidney damage or kidney failure
• retinopathy or blindness

Atherosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as blood flows through them. High blood pressure can make the artery walls thicken and harden. When artery walls thicken, the inside of the blood vessel narrows. Cholesterol and fats are more likely to build up on the walls of damaged arteries, making them even narrower. Blood clots also can get trapped in narrowed arteries, blocking the flow of blood. When atherosclerosis occurs in the blood vessels leading to the legs and feet, it is called peripheral vascular disease. Blood flow is decreased to the legs and feet with peripheral vascular diseases and can cause poor circulation in the legs, claudication, or aneurysm.

Arteries narrowed by atherosclerosis may not deliver enough blood to organs and other tissues. Reduced or blocked blood flow to the heart can cause a heart attack. If an artery to the brain is blocked, a stroke can result.

Hypertension makes the heart work harder to pump blood through the body. The extra workload can make the heart muscle thicken and stretch. When the heart becomes enlarged it cannot pump enough blood. If the hypertension is not treated, the heart may fail.

The kidneys remove the body's wastes from the blood. If hypertension thickens the arteries to the kidneys, less waste can be filtered from the blood. As the condition worsens, the kidneys fail and wastes build up in the blood. Dialysis or a kidney transplant is needed when the kidneys fail.

Hypertension can cause damage to blood vessels in the eyes, leading to retinopathy, or damage to the retina. Retinal damage becomes severe when blood pressure levels are high and remain elevated for a prolonged period of time.

Demographics

In the United States, an estimated 5–10 percent of children have hypertension, and one in four adults (about 50 million) have hypertension. About 30 percent of those with hypertension do not know they have it. Hypertension is more common in men than women and in people over age 65 than in younger persons. It also is more frequent and severe in African-American and Mexican-American adults and children than in white Americans. The prevalence of high blood pressure among African-Americans and whites in the southeastern United Statesis greater, and death rates from stroke are higher than among those in other regions.

In the early 2000s, high blood pressure in children and adolescents is on the rise. A 2003 report indicated this increase is most likely due to a greater number of overweight and obese children and adolescents. The U.S. Centers for Disease Control and Prevention studied the health and nutrition of Americans in the National Health and Nutrition Examination Surveys for more than 40 years, and the last data were collected in 2000. Researchers found a trend of high blood pressure in children ages eight to 17 years who were overweight or obese.

Causes and symptoms

Causes

Many different actions or situations can normally raise blood pressure. Physical activity and changes in position can temporarily raise blood pressure. Stressful situations can make blood pressure go up. When the stress goes away, blood pressure usually returns to normal. Certain medications also may change blood pressure, but usually blood pressure returns to normal when the drug is discontinued. These temporary increases in blood pressure are not considered hypertension. A diagnosis of hypertension is made only when a person has at least three separate high blood pressure readings performed one to several weeks apart.

Hypertension without a known cause is called primary or essential hypertension. Although the cause of hypertension is unknown in 90–95 percent of adults, primary hypertension is uncommon in children, occurring in less than 1–2 percent of hypertensive children.

When a child has hypertension caused by another medical condition, it is called secondary hypertension. Secondary hypertension can be caused by a number of different illnesses. Kidney disease causes hypertension in 80–85 percent of childhood cases. The kidneys regulate the balance of salt and water in the body. If the kidneys cannot rid the body of excess salt and water, blood pressure goes up. Kidney infections, a narrowing of the arteries that carry blood to the kidneys, called renal artery stenosis, and other kidney disorders can disturb the salt and water balance.

As body weight increases, blood pressure rises. Being overweight or obese is the strongest predictor of hypertension in young adults. Obesity has steadily increased in children and adolescents over the years. An estimated 16 percent of school-age children are over-weight. High blood pressure develops about 10 years after a young person becomes overweight. Obesity may cause other cardiovascular diseases if it is not managed or treated properly.

Risk factors

Risk factors are conditions that increase the chance of developing hypertension. Some of these risk factors can be changed to reduce the risk of developing hypertension or to lower blood pressure:

• being overweight or obese
• lack of physical activity
• a diet high in fat, salt, and sugar
• heredity
• low birth weight and subsequent rapid weight gain
• male sex
• race
• congenital conditions, such as coarctation of the aorta
• diabetes
• kidney disease
• in adolescents, heavy alcohol consumption and use of oral contraceptives
• in adults, being over the age of 60

Although smoking is not directly related to high blood pressure in children and adolescents, those who smoke should stop to reduce their risk of developing other health problems such as coronary artery disease.

Some risk factors for hypertension can be changed, while others cannot. Some children inherit a tendency to develop hypertension, and the risk increases if both parents are hypertensive. Children who have the risk factors above can work with their doctor and family to manage the controllable risk factors.

Symptoms

Hypertension generally does not cause symptoms. When symptoms occur, they are usually mild and non-specific. In young children (age three and younger), symptoms may include:

• irritability
• excessive crying
• failure to gain weight
• poor feeding
• low-grade fever

In older children, symptoms may include:

• dizziness
• headaches
• vomiting
• heart palpitations

In severe and acute (sudden-onset) cases, hypertension can cause seizures, swelling throughout the body, blindness, or renal (kidney) failure. All of these symptoms require immediate medical attention and hospitalization .

When to call the doctor

If a child has any of the following symptoms, the parent or caregiver should call the child's doctor:

• unexplained headache
• sudden or gradual changes in vision
• dizziness or light-headedness that does not resolve with rest
• nausea associated with headache
• unexplained or uncontrollable vomiting
• heart palpitations

If a child has any of these symptoms, the parent or caregiver should immediately seek emergency medical attention:

• severe headache
• fainting
• seizures or convulsions
• swelling throughout the body
• unexplained blurred vision or vision loss
• severe chest pain or shortness of breath
• unexplained sudden weakness

Diagnosis

Blood pressure in children should be checked regularly: at least at every doctor's visit after age three. Early detection and treatment of hypertension improve the child's overall health and decrease the risk of future health problems associated with hypertension.

Blood pressure is measured with an instrument called a sphygmomanometer. A cloth-covered rubber cuff is wrapped around the upper arm and inflated. When the cuff is inflated, an artery in the arm is squeezed to momentarily stop the flow of blood. Then, the air is let out of the cuff while a stethoscope placed over the artery is used to detect the sound of the blood spurting back through the artery. This first sound is the systolic pressure, the pressure when the heart beats. The last sound heard as the rest of the air is released is the diastolic pressure, the pressure between heartbeats. Both sounds are recorded on the mercury gauge on the sphygmomanometer.

The arm cuff used to measure blood pressure in children must be appropriate to the child's size, or the reading may be inaccurate.

A typical physical examination to evaluate hypertension includes:

• medical and family history
• physical examination
• ophthalmoscopy: examination of the blood vessels in the eye
• blood and urine tests

The physical exam may include several blood pressure readings at different times and in different positions. For at least five minutes before the blood pressure reading is taken, the child should be seated in a chair, with feet on the floor and arms supported at heart level. For best results, the child should not eat or drink caffeinated products within the 30 minutes prior to the exam. The physician uses a stethoscope to listen to sounds made by the heart and blood flowing through the arteries.

During the physical exam, the child's pulse, reflexes, and height and weight are checked and recorded. Internal organs are palpated to determine if they are enlarged.

Because hypertension can cause damage to the blood vessels in the eyes, the eyes may be checked with a instrument called an ophthalmoscope. The physician will look for thickening, narrowing, or hemorrhages in the blood vessels.

Urine and blood tests may be done to evaluate health and to detect the presence of certain substances that may indicate an underlying condition that is causing the hypertension.

Usually blood tests and urine tests, along with the physical examination and medical history, are enough to make the diagnosis of hypertension. If necessary, to rule out other medical conditions or to assess any damage from hypertension and/or its treatment, the following tests may be performed:

• Chest x ray: To detect an enlarged heart, other vascular abnormalities, or lung disease.
• Electrocardiogram (ECG): To measure the electrical activity of the heart. It can detect if the heart muscle is enlarged and if there is damage to the heart muscle from blocked arteries.
• Echocardiogram (echo): To produce a graphic outline of the heart's movement, valves, and chambers, used to evaluate the function of the heart and valves. Echo is often combined with Doppler ultrasound and color Doppler. During the echo, an ultrasound transducer (hand-held wand placed on the skin of the chest) emits high-frequency sound waves to produce pictures of the heart's valves and chambers. An echo is used in pediatric patients diagnosed with hypertension to determine the extent of left ventricular hypertrophy, a condition in which the heart's main pumping vessel is enlarged.

Treatment

There is no cure for primary hypertension, but blood pressure can almost always be lowered with the correct treatment. The goal of treatment is to lower blood pressure to levels that will prevent heart disease and other complications of hypertension that could manifest in adulthood. In secondary hypertension, the disease that is responsible for the hypertension is treated in addition to the hypertension itself. Successful treatment of the underlying disorder may cure the secondary hypertension.

Clinicians should work with the child and the parents or caregivers to develop an individual treatment plan. Specific treatment goals vary. Treatment should be provided by a pediatric cardiologist or pediatrician with special knowledge and experience in the treatment of high blood pressure.

Lifestyle changes

Depending on the results of diagnostic tests, childhood hypertension is generally treated with lifestyle changes, including diet and exercise , before antihypertensive medication is prescribed. Lifestyle changes that may reduce blood pressure include:

• losing weight
• exercising regularly
• reducing fat, salt, and sugar in the diet
• managing stress and anxiety
• quitting smoking and reducing alcohol consumption, as applicable in older children

Reaching and maintaining a healthy body weight is important. Overweight children with hypertension are recommended to lose weight until they are within 15 percent of their healthy body weight. Even a small amount of weight loss can make a major difference. Physical activities should be encouraged, and sedentary activities such as watching television or playing video games should be limited. The recommended exercise goal is aerobic activity, such as brisk walking, at least 30 minutes per day, most days of the week.

A pediatrician can calculate a healthy range of body weight for the child, recommend dietary guidelines, and provide activity guidelines to help the child safely and effectively lose weight. A consultation with a registered dietitian also may assist the parent or caregiver in implementing dietary changes.

Nutritional concerns

Dietary guidelines are individualized, based on the child's blood pressure levels and specific needs. In children older than two years of age, the following low-fat dietary guidelines are recommended:

• Total fat intake should comprise 30 percent or less of total calories consumed per day.
• Calories consumed as saturated fat should equal no more than 8 to 10 percent of total calories consumed per day.
• Total cholesterol intake should be less than 300 mg/dl per day.

Elevated blood pressure can be reduced by an eating plan that emphasizes fruits, vegetables, and low-fat dairy foods, and which is low in saturated fat, total fat, and cholesterol. The DASH diet is recommended for patients with hypertension and includes whole grains, poultry, fish, and nuts. Fats, red meats, sodium, sweets, and sugar-sweetened beverages are limited. Sodium should also be reduced to no more than 1,500 milligrams per day.

A gradual transition to a heart-healthy diet can help decrease a child's risk of coronary artery disease and other health conditions in adulthood. Parents can replace foods high in fat with grains, vegetables, fruits, lean meat, and other foods low in fat and high in complex carbohydrates and protein. They can resist adding salt to foods while cooking and avoid highly processed foods that are usually high in sodium, such as fast foods, canned foods, boxed mixes, and frozen meals.

Alternative treatment

Alternative and complementary therapies include approaches that are considered to be outside the mainstream of traditional health care.

Techniques that induce relaxation and reduce stress, such as yoga , tai chi, meditation, guided imagery, and relaxation training, may be helpful in controlling blood pressure. Acupuncture and biofeedback training also may help induce relaxation. Before learning or practicing any particular technique, it is important for the parent/caregiver and child to learn about the therapy, its safety and effectiveness, potential side effects, and the expertise and qualifications of the practitioner. Although some practices are beneficial, others may be harmful to certain patients.

Dietary supplements, including garlic, fish oil (omega-3 fatty acids), L-arginine, soy, coenzyme Q10, phytosterols, and chelation therapy may be beneficial, but the exact nature of their effects on blood pressure is unknown. There is little scientific evidence that these therapies lower blood pressure or prevent the complications of high blood pressure, and most of these supplements have not been studied extensively in children and adolescents.

Vitamin E and beta carotene supplements were once thought to help prevent the development of heart disease, but subsequent studies disprove that assumption.

Medications

Medications usually are not prescribed for children as a first-line treatment for hypertension. Medications are prescribed, however, to treat hypertension when the child has significant high blood pressure or organ damage, or when diet and exercise are not adequately controlling the child's blood pressure.

Follow-up care

Follow-up care for hypertension includes home blood pressure monitoring. The parent or caregiver checks the child's blood pressure at different times of the day and records the readings. The doctor reviews this blood pressure record during the child's check-ups to evaluate the effectiveness of the child's treatment and to make any necessary adjustments.

Depending on the child's blood pressure levels and presence of other medical conditions such as diabetes, the doctor may recommend annual eye exams to detect the presence of vision changes and the development of retinopathy.

Prognosis

There is no cure for hypertension. However, it can be well controlled with the proper treatment. Therapy with a combination of lifestyle changes and sometimes antihypertensive medicines usually can manage blood pressure. For most children, early primary hypertension causes no immediate risk of serious health problems, but it does increase the risk for future organ damage. The key to avoiding serious complications of hypertension is to detect and treat it at the earliest possible age so that preventive treatment can be initiated.

Prevention

Avoiding or eliminating known risk factors helps reduce the risk of developing hypertension. Making the same changes recommended for treating hypertension can reduce a child's risk of developing hypertension:

• losing weight if overweight or obese
• exercising regularly
• reducing salt, fat, and sugar in the diet
• reducing fat intake
• managing stress and anxiety
• quitting smoking and limiting alcohol, as applicable in older children

Parental concerns

Parents should reinforce with the child that hypertension is a serious condition that can cause more health problems later in life. Parents should work with their child to make dietary changes and increase their activity level to manage hypertension and prevent it from getting worse. Everyone can benefit when a heart-healthy lifestyle is followed, so the dietary and activity changes made for the hypertensive child will benefit the entire family.

Resources

BOOKS

McGoon, Michael D., and Bernard J. Gersh, eds. Mayo Clinic Heart Book: The Ultimate Guide to Heart Health, 2nd ed. New York: William Morrow and Co., Inc., 2000.

Moore, Thomas, et al. The Dash Diet for Hypertension: Lower Your Blood Pressure in Fourteen Days without Drugs. New York: Simon & Schuster, Inc., 2001.

Topol, Eric J. Cleveland Clinic Heart Book: The Definitive Guide for the Entire Family from the Nation's Leading Heart Center. New York: Hyperion, 2000.

Trout, Darrell, and Ellen Welch. Surviving with Heart: Taking Charge of Your Heart Care. Golden, CO: Fulcrum Publishing, 2002.

PERIODICALS

McNamara, Damian. "Obesity Behind Rise in Incidence of Primary Hypertension." Family Practice News (April 1, 2003): 45–51.

——. "Trial Shows Efficacy of Lifestyle Changes for Blood Pressure: More Intensive than Typical Office Visit." Family Practice News (July 1, 2003): 1–2.

"New Blood Pressure Guidelines Establish Diagnosis of Prehypertension: Level Seeks to Identify At-risk Individuals Early." Case Management Advisor (July 2003): S1.

Sorof, Jonathan M., et al. "Cardiovascular risk factors and sequelae in hypertensive children identified by referral versus school-based screening." Hypertension 43 (2004): 214.

KEY TERMS

Aneurysm —A weakened area in the wall of a blood vessel which causes an outpouching or bulge. Aneurysms may be fatal if these weak areas burst, resulting in uncontrollable bleeding.

Aorta —The main artery located above the heart that pumps oxygenated blood out into the body. The aorta is the largest artery in the body.

Arteriosclerosis —A chronic condition characterized by thickening, loss of leasticity, and hardening of the arteries and the build-up of plaque on the arterial walls. Arteriosclerosis can slow or impair blood circulation. It includes atherosclerosis, but the two terms are often used synonymously.

Artery —A blood vessel that carries blood away from the heart to the cells, tissues, and organs of the body.

Atrial —Referring to the upper chambers of the heart.

Claudication —Cramping or pain in a leg caused by poor blood circulation. This condition is frequently caused by hardening of the arteries (atherosclerosis). Intermittent claudication occurs only at certain times, usually after exercise, and is relieved by rest.

Coarctation of the aorta —A congenital defect in which severe narrowing or constriction of the aorta obstructs the flow of blood.

Dialysis —A process of filtering and removing waste products from the bloodstream, it is used as a treatment for patients whose kidneys do not function properly. Two main types are hemodialysis and peritoneal dialysis. In hemodialysis, the blood flows out of the body into a machine that filters out the waste products and routes the cleansed blood back into the body. In peritoneal dialysis, the cleansing occurs inside the body. Dialysis fluid is injected into the peritoneal cavity and wastes are filtered through the peritoneum, the thin membrane that surrounds the abdominal organs.

Diastolic blood pressure —Diastole is the period in which the left ventricle relaxes so it can refill with blood; diastolic pressure is therefore measured during diastole.

Heart attack —Damage that occurs to the heart when one of the coronary arteries becomes narrowed or blocked.

Obesity —An abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight.

Overweight —Being 25 to 29 percent over the recommended healthy body weight for a specific age and height, as established by calculating body mass index.

Retinopathy —Any disorder of the retina.

Sphygmomanometer —An instrument used to measure blood pressure.

Stroke —Interruption of blood flow to a part of the brain with consequent brain damage. A stroke may be caused by a blood clot or by hemorrhage due to a burst blood vessel. Also known as a cerebrovascular accident.

Systolic blood pressure —Blood pressure when the heart contracts (beats).

Ventricles —The lower pumping chambers of the heart. The ventricles push blood to the lungs and the rest of the body.

ORGANIZATIONS

American College of Cardiology. Heart House, 9111 Old Georgetown Rd., Bethesda, MD 20814–1699. Web site: <www.acc.org>.

American Heart Association. 7320 Greenville Ave., Dallas, TX 75231. Web site: <www.americanheart.org>.

American Society of Hypertension. 148 Madison Ave., 5th Floor, New York, NY 10016. Web site: <www.ash-us.org>.

The Cleveland Clinic Heart Center. The Cleveland Clinic Foundation, 9500 Euclid Ave., F25, Cleveland, OH 44195. Web site: <www.clevelandclinic.org/heartcenter>.

Toni Rizzo Teresa G. Odle Angela M. Costello

Hypertension

Definition

Hypertension, also called high blood pressure , occurs when the pressure of blood against artery walls as it flows throughout the body is higher than normal. Prolonged high blood pressure can seriously damage not only blood vessels but the heart and other organs.

Description

Hypertension is not technically a disease, but is an indication that something is wrong within the circulatory system, which includes the heart and the blood vessels. Normally, when the heart beats, blood is pumped throughout the body by way of an intricate network of blood vessels. The arteries take blood to the capillaries that nourish the cells, and the veins return the blood to the heart, where it is oxygenated by the lungs and then pumped from the heart again. When something constricts the arterial walls, then pressure within the artery is increased. This results in a high blood pressure reading.

Blood pressure is measured with a stethoscope and a sphygmomanometer, which consists of a blood

pressure cuff that is place around the upper arm and a measuring device. A healthcare provider will pump up the blood pressure cuff until it is tight around the arm and will listen to the flow of the blood within the artery. Blood pressure is recorded using two numbers, one on the top and one the bottom. Systolic pressure occurs when the heart beats. This is when the heart is working and is the top number in a blood pressure reading. The diastolic pressure, or the bottom number, is when the heart relaxes. Until 2003, normal blood pressure was considered under 140/90. The National Heart, Lung, and Blood Institute (NHLBI) lowered those guidelines to under 120/80 and created a new category of hypertension called prehypertension.

High blood pressure can lead to serious complications, including stroke, heart attack, heart disease , or kidney damage. Since hypertension makes the heart work harder, the muscles of that organ can become stretched or thickened. This is a condition called an enlarged heart. Though one might think that a stronger muscle would work better, in the case of the heart, an enlarged heat means that the muscle itself has become weaker. This can lead to heart failure.

Arteries can become blocked due to clots or the build up of plaque, causing blood flow to narrow to vital organs. This causes stroke and heart attack.

The aging process can sometimes cause arteriosclerosis or hardening of the arteries, which can make pumping blood throughout the body much more difficult, creating high blood pressure. This also can limit vital nutrients and oxygen to organs in the body. The brain is especially susceptible to inadequate blood flow.

When the arteries to the kidneys become narrowed, the kidneys filter less blood, and wastes can build up. The kidneys can fail, resulting in the need for dialysis or a kidney transplant. Nearly a fourth of those on kidney dialysis have kidney failure because of hypertension.

Because blood vessels are also working hard, bulges or aneurysms can form. These become weakened places that can burst, which can cause stroke, disability, and death . Aneurysms are commonly found in the aorta, the main artery leading away from the heart, as well as in the brain, the intestines, and the legs.

Hypertension can also affect the eyes by blocking veins in the retina, causing aneurysms in and around the eye, and even swelling the base of the optic nerve. These changes can impair vision and even cause blindness.

Types of hypertension

With the new blood pressure guidelines by the NHLBI in 2003, hypertension has been categorized differently.

Prehypertension is a blood pressure reading above 120/80 but under 140/90. This type of high blood pressure increases the risk of developing hypertension later in life. It is usually treated with lifestyle changes. However, if a patient has diabetes or kidney disease, the doctor may need to treat this type of hypertension with medication.

Primary hypertension occurs when the blood pressure reading is 140/90 or above. This type of high blood pressure is also called essential hypertension or idiopathic hypertension. It has no known cause and occurs in 90 percent of high blood pressure patients. There are two stages of this condition. Stage I has blood pressure that ranges from 140/90 to under 160/100. Stage II has readings over 160/100.

Secondary hypertension also has a blood pressure reading of 140/90 or above. This type of high blood pressure is due to an underlying medical condition.

Isolated systolic hypertension is a type of high blood pressure that is concerned with high systolic pressure, even though the diastolic pressure can be within normal levels. Diastolic pressure increases with age until about 50, and then it levels off or even decreases. Systolic pressure increases with age due to other circulatory conditions such as arteriosclerosis or heart problems. Isolated systolic hypertension is the most common form of hypertension for older adults, with nearly 65 percent of high blood pressure patients over 60 reporting having this type. It is also the least likely of all types of hypertension to be treated well. The NHLBI has recommended that systolic blood pressure be the key criterion for diagnosing hypertension in older adults.

White coat hypertension is an increase in blood pressure due to becoming stressed in the doctor's office. Usually, patients with this condition have normal readings when their blood pressure is taken in other settings. Many doctors who suspect a patient of having white coat hypertension will suggest that a patient take blood pressure readings at home with a home blood pressure monitor and report the findings to the doctor.

Risk factors

There are some risk factors that pre-dispose some patients to having hypertension. Some of these factors reflect lifestyle choices and therefore can be changed, thus reducing the risk of developing hypertension. Others cannot. Age, gender, race, and having a family history of high blood pressure are examples of factors that cannot be changed. The risk of developing hypertension increases with age. Men have a greater chance of developing high blood pressure before age 55, and more women have it after menopause . Hypertension tends to run in families, and African Americans have a greater risk of developing it.

Demographics

Nearly 73 million American adults have hypertension, and half of them are women. More than 40 percent of African Americans have high blood pressure, and they have it at an earlier age and with more severity than other ethnic groups. Almost half of all people over age 50 have hypertension. Moreover, almost two-thirds of Americans with high blood pressure do not have the condition under adequate control. Women diagnosed with pre-hypertension have a 100 percent increase in risk of developing hypertension, whereas men with the condition only have a 45 percent increase. In 2003, a study revealed a rise in the incidence of high blood pressure among children and teenagers due to increased obesity rates.

Causes and symptoms

Causes

Blood pressure can vary throughout the day. It can also increase with physical activity or stress . Patients may also have elevated blood pressure due to taking cold medications containing pseudoephedrin or nonsteroid anti-inflammatory drugs such as aspirin or ibuprofen. In most cases, blood pressure returns to normal when the activity or medications are stopped. Pregnancy can also elevate blood pressure and should be monitored since it can lead to pre-eclamsia, a condition that can be dangerous to mother and baby. In most cases, hypertension in pregnancy is temporary.

Sustained high blood pressure, however, often has no known cause. Nevertheless, patients with secondary hypertensionmayhave it because of a numberof medical conditions, including kidney disease, thyroid disorders, diseases or tumors of the adrenal gland, Cushing's syndrome (a condition where there is too much corticosteroid hormone in the blood), narrowing of the arteries, or sleep apnea. The underlying condition must be treated in addition to hypertension.

Symptoms

Called the silent killer, hypertension often has no symptoms. Some patients, however, may report headache, blurred vision, nosebleeds, dizziness , shortness of breath, drowsiness, confusion, or even numbness or tingling in the hands or feet. The only way hypertension is diagnosed is by checking blood pressure with a sphygmomanometer.

Diagnosis

Hypertension is usually not diagnosed by one blood pressure reading since other factors can temporarily raise blood pressure, such as anxiety or too much caffeine . Doctors will usually take blood pressure readings over many days or ask the patient to use a blood pressure monitor at home and record the readings, making sure to check blood pressure at the same time each day. Sometimes, doctors will take two or three blood pressure readings during an office visit.

If the initial reading is quite high, for example it is 180/110, or if there are symptoms of an underlying disease that could produce secondary hypertension, the doctor may treat hypertension immediately. Generally, a high blood pressure reading over 160/100 should be treated and checked again within two weeks. Those readings between 140/90 and 159/99 should be rechecked within a month, and prehypertensive patients can be monitored every six months. A normal reading only requires a yearly recheck.

In order to take a proper blood pressure reading, the patient should avoid tobacco and caffeine a half hour before having blood pressure taken and should sit quietly for five minutes before the test. The patient should sit in a chair with both feet on the floor, and the arm that is used should be supported at heart level. Some healthcare providers will ask the patient to rest the arm on a desk or table. Often the patient is asked to wear short sleeves.

Some patients may have upper arms that are bigger than the standard blood pressure cuff. In that case, the healthcare provider may use a larger cuff. Some patients may have a slightly lower reading with a larger cuff.

The doctor will also take a thorough family history, asking questions about chest pain , kidney disease, diabetes, or thyroid disease. The patient will be asked about family members who have hypertension or heart disease.

A physical exam usually follows the medical history. Sometimes, the doctor will listen to blood flow sounds with a stethoscope not only in the chest but in the neck, abdomen, or groin to see if there are blocked arteries. The doctor will also examine the small blood vessels in the back of the eyes to look for damage from undiagnosed high blood pressure.

In many cases, other tests are not required unless the patient has other factors that warrant further study. The doctor may order blood tests, an electrocardiogram, or even a chest x ray .

Treatment

Treating hypertension can reduce a patient's risk of having a stroke by 38 percent or a heart attack by 27 percent. If there is an underlying cause of hypertension, treating that condition will reduce blood pressure. Sometimes the doctor will recommend hypertension medication in addition to the medications for the underlying condition.

For patients with primary hypertension, the doctor usually recommends a combination of lifestyle changes and medication. Lifestyle changes include eating a healthy diet , reducing salt, and quitting smoking . Patients also are urged to get enough sleep and to manage stress through a variety of techniques including deep breathing and meditation.

Many people with hypertension may also be overweight, causing the heart to work harder. Even a moderate reduction of ten pounds can reduce blood pressure. Patients are also encouraged to exercise at least 30 minutes every day. NHLBI suggests that exercise does not need to be sport-oriented, but may include walking and household chores, such as washing the car, gardening, raking leaves, washing windows, or even pushing a baby stroller.

Patients with prehypertension are educated about their risk of developing primary hypertension. Lifestyle changes are encouraged, but no medication is usually given, though some doctors may do so.

Medications

Hypertension medications will not cure the condition but will help patients keep their blood pressure readings within normal levels. Coupled with lifestyle changes, many patients may reduce the amount of high blood pressure medications they need.

There are nine types of medications used to treat hypertension. Different types work on the mechanisms of hypertension in different ways. In initial treatment, doctors may need to try different medications or different combinations of medications for each patient. Sometimes, that results in smaller doses of each medication when combined than would be needed with only one type of drug. Additionally, each of these medications may cause unpleasant side effects. The doctor may try a few different drugs before finding the one that a patient can tolerate.

Diuetics are sometimes called water pills because they increase the kidney's ability to flush excess water and sodium from the body. Having less fluid to carry, the arteries have less pressure within them. Diuretics are the first drug of choice in the treatment of hypertension and often are combined with other drugs. One of the most common diuretics is hydrocholorothiazide. Diuretics increase the frequency of urination and can flush potassium from the body. Patients taking these drugs may need to monitor their potassium levels and eat foods rich in potassium or take a potassium supplement.

Beta-blockers reduce nerve impulses to the arteries and the heart, causing the heart to work less and beat slower. Blood pressure is reduced because the heart is pumping less blood through the arteries.

Calcium channel blockers (CCBs) stop calcium from entering the arteries and the heart. One type of CCB slows the heart and opens up the arteries. Newer CCBs only dilate the arteries but have no effect on how hard the heart works.

Angiotensin converting enzyme inhibitors (ACE inhibitors) inhibit angiotensin II, a hormone that causes arteries to narrow. This medication allows the arteries to relax, thus reducing blood pressure. ACE inhibitors are often used in combination with diuretics. They also can raise potassium levels and can affect kidney function.

Angiotensin antagonists or angiotensin II receptor blockers (ARBS) are similar to ACE inhibitors because they stop the production of angiotensin II, but these drugs also widen the arteries. ARBS have few side effects.

Alpha-blockers reduce nerve impulses that cause the arteries to constrict. The blood flows freely and blood pressure goes down.

Alpha-beta blockers are combined drugs, slowing the heart and reducing the nerve impulses to constrict the arteries.

Vasodilators relax the muscles in the blood vessel walls, opening up the arteries allowing blood to flood.

Peripheral acting adrenergic antagonists work on the nervous system to relax the muscles of the artery walls and slow the heart. They often are used with diuretics. These drugs can cause lethargy and slowed mental functioning.

Nervous system inhibitors control nerve impulses from the brain that allow the arteries to relax.

Centrally acting agonists work directly on the brain to reduce blood pressure. They can often cause depression or drowsiness.

Alternative treatment

Herbal medicine has been helpful for some patients. However, these substances should be used with caution and under the direction of a qualified herbalist since even small doses may be potentially dangerous. Among the herbs recommended for hypertension are Coleus forshohlii, hawthorne, mistletoe, and rauwolfia.

Nutrition/Dietetic concerns

Dietary changes can help manage hypertension. The Dietary Approaches to Stop Hypertension, or DASH, diet has been highly recommended because it offers a well-balanced plan that is low in fat, cholesterol, red meat, and sugar. It is also low in salt. Patient should eat a healthy diet low in saturated fat and cholesterol and rich in whole grains, fruits, vegetables, and low-fat dairy products. Protein should come from lean meats, poultry, and fish.

A Harvard study in 2007 found that eating low-fat dairy products and other foods rich in calcium and vitamin D helped reduce hypertension in women aged 45 and older. Additionally, the NHLBI also recommends increasing potassium intake to 4,600 mg. a day.

Salt has been a factor in high blood pressure because it increases the volume of the blood flowing through the arteries in the body. Reducing the amount of salt you eat can reduce blood volume. Most salt comes from processed foods, therefore patients need to read food labels and avoid fast foods that are high in salt. Sodium should be limited to between 1,500 mg to 2,400 mg a day. That is three-fourths of a teaspoon to about a teaspoon and a fourth of salt. Table salt can be replaced with herbs and spices.

Some doctors may recommend that patients with hypertension reduce the amount of caffeine in their diets. This includes not only coffee and tea, but chocolate and carbonated drinks.

KEY TERMS

Aneurysm —A bulge in an artery.

Cushing's syndrome —A condition where there is too much corticosteroid hormone in the blood, which can cause hypertension.

Diastolic pressure —The pressure on the arteries when the heart relaxes.

Diuetics —A class of blood pressure medication, sometimes called water pills, that increase the kidney's ability to flush excess water and sodium from the bloodstream.

Pre-eclamsia —A dangerous condition in pregnancy, involving high blood pressure and protein in the urine.

Sphygmomanometer —An instrument used to measure blood pressure.

Systolic pressure —The pressure on the arteries when the heart beats.

In addition, patients are asked to limit the amount of alcohol they drink. A man should have no more than two drinks a day, and a woman should only have one.

Prognosis

There is no cure for hypertension, though it can be managed and serious complications can be avoided. Many times, weight loss and exercise can reduce the amount of medication that a patient needs, and in some cases moderate hypertension may be reversed.

Prevention

Hypertension can be avoided by quitting smoking, eating a proper diet, exercising, maintaining a proper weight, using less salt, drinking in moderation, and managing stress. For some individuals with family histories of high blood pressure, prevention may not be possible. Nevertheless, the onset of hypertension may be delayed or the severity of the disorder may be lessened through lifestyle changes and/or medication.

Caregiver concerns

The healthcare provider will need to educate patients about hypertension and what patients can do to manage this disease. Patients may need to consult a dietician to help them develop a healthy eating plan to lose weight or eliminate salt from their diets. Patients may need encouragement or creative ways to exercise more.

Importantly, careful monitoring of medication is essential, looking for side effects and checking kidney function and potassium levels. With elderly patients, the healthcare provider may need to suggest techniques for remembering to take medications every day at the same time of day. This may necessitate enlisting loved ones into reminding these patients.

Resources

PERIODICALS

“Diagnosing hypertension.” Hypertension (Harvard Special Health Report) (2007):21.

“Dietary approaches to stop hypertension (The DASH Diet) (Cardiology Advisor 2007).” Clinical Reference Systems (May 2007).

“Halting hypertension with a healthy diet.” Harvard Health commentaries (August 2006).

“High blood pressure: Common, commonly uncontrolled, and dangerous.” Staying Healthy from the Faculty of the Harvard Medical School (August 2006).

“High blood pressure: Secondary hypertension (Adult Health Advisor 2007).” Clinical Reference System (May 2007).

“How low should your blood pressure be?.” Harvard health commentaries (January 2007).

“Hypertension.” CareNotes (May 2007).

Wang, Lu; Manson, JoAnne E.; Buring, Julie E; Lee, I-Min; and Sesso, Howard D. “Dietary intake of dairy products, calcium, and vitamin D and the risk of hypertension in middle-aged and older women.” Hypertension (February 2008).

OTHER

NIH Senior Health. http://www.nihseniorhealth.gov.

ORGANIZATIONS

American Heart Association National Center, 7272 Greenville Avenue, Dallas, Texas, 75231-4596, 800 242-8721, http://www.americanheart.org.

American Society of Hypertension, 148 Madison Avenue, Fifth Floor, New York, New York, 10016, 212-696 9099, 212-696-0711, http://www.ash-us.org.

National Heart, Lung, and Blood Institute (NHLBI), PO Box 30105, Bethesda, Maryland, 20824-0105, 301-592 73, http://www.nhlbi.nih.gov.

National Institute on Aging (NIA), 31 Center Drive, MSC 2292, Building 31, Room 5C27, Bethesda, Maryland, 20892, 301-496-1752, 301-496-1072, http://www.nia.nih.gov.

Janie F. Franz

Hypertension

Definition

Hypertension is high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries as it flows through them. Arteries are the blood vessels that carry oxygenated blood from the heart to the body's tissues.

Description

As blood flows through arteries it pushes against the inside of the artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure will be. The size of small arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls narrow, or constrict.

Blood pressure is highest when the heart beats to push blood out into the arteries. When the heart relaxes to fill with blood again, the pressure is at its lowest point. Blood pressure when the heart beats is called systolic pressure. Blood pressure when the heart is at rest is called diastolic pressure. When blood pressure is measured, the systolic pressure is stated first and the diastolic pressure second. Blood pressure is measured in millimeters of mercury (mm Hg). For example, if a person's systolic pressure is 120 and diastolic pressure is 80, it is written as 120/80 mm Hg. The American Heart Association has long considred blood pressure less than 140 over 90 normal for adults. However, the National Heart, Lung, and Blood Institute in Bethesda, Maryland released new clinical guidelines for blood pressure in 2003, lowering the standard normal readings. A normal reading was lowered to less than 120 over less than 80.

Hypertension is a major health problem, especially because it has no symptoms. Many people have hypertension without knowing it. In the United States, about 50 million people age six and older have high blood pressure. Hypertension is more common in men than women and in people over the age of 65 than in younger persons. More than half of all Americans over the age of 65 have hypertension. It also is more common in African-Americans than in white Americans.

Hypertension is serious because people with the condition have a higher risk for heart disease and other medical problems than people with normal blood pressure. Serious complications can be avoided by getting regular blood pressure checks and treating hypertension as soon as it is diagnosed.

If left untreated, hypertension can lead to the following medical conditions:

• arteriosclerosis, also called atherosclerosis
• heart attack
• stroke
• enlarged heart
• kidney damage.

Arteriosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as blood flows through them. High blood pressure can make the artery walls thicken and harden. When artery walls thicken, the inside of the blood vessel narrows. Cholesterol and fats are more likely to build up on the walls of damaged arteries, making them even narrower. Blood clots also can get trapped in narrowed arteries, blocking the flow of blood.

Arteries narrowed by arteriosclerosis may not deliver enough blood to organs and other tissues. Reduced or blocked blood flow to the heart can cause a heart attack. If an artery to the brain is blocked, a stroke can result.

Hypertension makes the heart work harder to pump blood through the body. The extra workload can make the heart muscle thicken and stretch. When the heart becomes too enlarged it cannot pump enough blood. If the hypertension is not treated, the heart may fail.

The kidneys remove the body's wastes from the blood. If hypertension thickens the arteries to the kidneys, less waste can be filtered from the blood. As the condition worsens, the kidneys fail and wastes build up in the blood. Dialysis or a kidney transplant are needed when the kidneys fail. About 25% of people who receive kidney dialysis have kidney failure caused by hypertension.

Causes and symptoms

Many different actions or situations can normally raise blood pressure. Physical activity can temporarily raise blood pressure. Stressful situations can make blood pressure go up. When the stress goes away, blood pressure usually returns to normal. These temporary increases in blood pressure are not considered hypertension. A diagnosis of hypertension is made only when a person has multiple high blood pressure readings over a period of time.

The cause of hypertension is not known in 90 to 95 percent of the people who have it. Hypertension without a known cause is called primary or essential hypertension.

When a person has hypertension caused by another medical condition, it is called secondary hypertension. Secondary hypertension can be caused by a number of different illnesses. Many people with kidney disorders have secondary hypertension. The kidneys regulate the balance of salt and water in the body. If the kidneys cannot rid the body of excess salt and water, blood pressure goes up. Kidney infections, a narrowing of the arteries that carry blood to the kidneys, called renal artery stenosis, and other kidney disorders can disturb the salt and water balance.

Cushing's syndrome and tumors of the pituitary and adrenal glands often increase levels of the adrenal gland hormones cortisol, adrenalin, and aldosterone, which can cause hypertension. Other conditions that can cause hypertension are blood vessel diseases, thyroid gland disorders, some prescribed drugs, alcoholism, and pregnancy.

Even though the cause of most hypertension is not known, some people have risk factors that give them a greater chance of getting hypertension. Many of these risk factors can be changed to lower the chance of developing hypertension or as part of a treatment program to lower blood pressure.

Risk factors for hypertension include:

• age over 60
• male sex
• race
• heredity
• salt sensitivity
• obesity
• inactive lifestyle
• heavy alcohol consumption
• use of oral contraceptives

Some risk factors for getting hypertension can be changed, while others cannot. Age, male sex, and race are risk factors that a person can't do anything about. Some people inherit a tendency to get hypertension. People with family members who have hypertension are more likely to develop it than those whose relatives are not hypertensive. People with these risk factors can avoid or eliminate the other risk factors to lower their chance of developing hypertension. A 2003 report found that the rise in incidence of high blood pressure among children is most likely due to an increase in the number of overweight and obese children and adolescents.

Diagnosis

Because hypertension doesn't cause symptoms, it is important to have blood pressure checked regularly. Blood pressure is measured with an instrument called a sphygmomanometer. A cloth-covered rubber cuff is wrapped around the upper arm and inflated. When the cuff is inflated, an artery in the arm is squeezed to momentarily stop the flow of blood. Then, the air is let out of the cuff while a stethoscope placed over the artery is used to detect the sound of the blood spurting back through the artery. This first sound is the systolic pressure, the pressure when the heart beats. The last sound heard as the rest of the air is released is the diastolic pressure, the pressure between heart beats. Both sounds are recorded on the mercury gauge on the sphygmomanometer.

Normal blood pressure is defined by a range of values. Blood pressure lower than 120/80 mm Hg is considered normal. A number of factors such as pain, stress or anxiety can cause a temporary increase in blood pressure. For this reason, hypertension is not diagnosed on one high blood pressure reading. If a blood pressure reading is 120/80 or higher for the first time, the physician will have the person return for another blood pressure check. Diagnosis of hypertension usually is made based on two or more readings after the first visit.

Systolic hypertension of the elderly is common and is diagnosed when the diastolic pressure is normal or low, but the systolic is elevated, e.g.170/70 mm Hg. This condition usually co-exists with hardening of the arteries (atherosclerosis).

Blood pressure measurements are classified in stages, according to severity:

• normal blood pressure: less than less than 120/80 mm Hg
• pre-hypertension: 120-129/80-89 mm Hg
• Stage 1 hypertension: 140-159/90-99 mm Hg
• Stage 2 hypertension: at or greater than 160-179/100-109 mm Hg

A typical physical examination to evaluate hypertension includes:

• medical and family history
• physical examination
• ophthalmoscopy: Examination of the blood vessels in the eye
• chest x ray
• electrocardiograph (ECG)
• blood and urine tests.

The medical and family history help the physician determine if the patient has any conditions or disorders that might contribute to or cause the hypertension. A family history of hypertension might suggest a genetic predisposition for hypertension.

The physical exam may include several blood pressure readings at different times and in different positions. The physician uses a stethoscope to listen to sounds made by the heart and blood flowing through the arteries. The pulse, reflexes, and height and weight are checked and recorded. Internal organs are palpated, or felt, to determine if they are enlarged.

Because hypertension can cause damage to the blood vessels in the eyes, the eyes may be checked with a instrument called an ophthalmoscope. The physician will look for thickening, narrowing, or hemorrhages in the blood vessels.

A chest x ray can detect an enlarged heart, other vascular (heart) abnormalities, or lung disease.

An electrocardiogram (ECG) measures the electrical activity of the heart. It can detect if the heart muscle is enlarged and if there is damage to the heart muscle from blocked arteries.

Urine and blood tests may be done to evaluate health and to detect the presence of disorders that might cause hypertension.

Treatment

There is no cure for primary hypertension, but blood pressure can almost always be lowered with the correct treatment. The goal of treatment is to lower blood pressure to levels that will prevent heart disease and other complications of hypertension. In secondary hypertension, the disease that is responsible for the hypertension is treated in addition to the hypertension itself. Successful treatment of the underlying disorder may cure the secondary hypertension.

Guidelines advise that clinicians work with patients to agree on blood pressure goals and develop a treatment plan for the individual patient. Actual combinations of medications and lifestyle changes will vary from one person to the next. Treatment to lower blood pressure may include changes in diet, getting regular exercise, and taking antihypertensive medications. Patients falling into the pre-hypertension range who don't have damage to the heart or kidneys often are advised to make needed lifestyle changes only. A 2003 report of a clinical trial showed that adults with elevated blood pressures lowered them as mush as 38% by making lifestyle changes and participating in the DASH diet, which encourages eating more fruit and vegetables.

Lifestyle changes that may reduce blood pressure by about 5 to 10 mm Hg include:

• reducing salt intake
• reducing fat intake
• losing weight
• getting regular exercise
• quitting smoking
• reducing alcohol consumption
• managing stress

Patients whose blood pressure falls into the Stage 1 hypertension range may be advised to take antihypertensive medication. Numerous drugs have been developed to treat hypertension. The choice of medication will depend on the stage of hypertension, side effects, other medical conditions the patient may have, and other medicines the patient is taking.

If treatment with a single medicine fails to lower blood pressure enough, a different medicine may be tried or another medicine may be added to the first. Patients with more severe hypertension may initially be given a combination of medicines to control their hypertension. Combining antihypertensive medicines with different types of action often controls blood pressure with smaller doses of each drug than would be needed for just one.

Antihypertensive medicines fall into several classes of drugs:

• diuretics
• beta-blockers
• calcium channel blockers
• angiotensin converting enzyme inhibitors (ACE inhibitors)
• alpha-blockers
• alpha-beta blockers
• vasodilators
• peripheral acting adrenergic antagonists
• centrally acting agonists

Diuretics help the kidneys eliminate excess salt and water from the body's tissues and the blood. This helps reduce the swelling caused by fluid buildup in the tissues. The reduction of fluid dilates the walls of arteries and lowers blood pressure. New guidelines released in 2003 suggest diuretics as the first drug of choice for most patients with high blood pressure and as part of any multi-drug combination.

Beta-blockers lower blood pressure by acting on the nervous system to slow the heart rate and reduce the force of the heart's contraction. They are used with caution in patients with heart failure, asthma, diabetes, or circulation problems in the hands and feet.

Calcium channel blockers block the entry of calcium into muscle cells in artery walls. Muscle cells need calcium to constrict, so reducing their calcium keeps them more relaxed and lowers blood pressure.

ACE inhibitors block the production of substances that constrict blood vessels. They also help reduce the build-up of water and salt in the tissues. They often are given to patients with heart failure, kidney disease, or diabetes. ACE inhibitors may be used together with diuretics.

Alpha-blockers act on the nervous system to dilate arteries and reduce the force of the heart's contractions.

Alpha-beta blockers combine the actions of alpha and beta blockers.

Vasodilators act directly on arteries to relax their walls so blood can move more easily through them. They lower blood pressure rapidly and are injected in hypertensive emergencies when patients have dangerously high blood pressure.

Peripheral acting adrenergic antagonists act on the nervous system to relax arteries and reduce the force of the heart's contractions. They usually are prescribed together with a diuretic. Peripheral acting adrenergic antagonists can cause slowed mental function and lethargy.

Centrally acting agonists also act on the nervous system to relax arteries and slow the heart rate. They are usually used with other antihypertensive medicines.

Prognosis

There is no cure for hypertension. However, it can be well controlled with the proper treatment. Therapy with a combination of lifestyle changes and antihypertensive medicines usually can keep blood pressure at levels that will not cause damage to the heart or other organs. The key to avoiding serious complications of hypertension is to detect and treat it before damage occurs. Because antihypertensive medicines control blood pressure, but do not cure it, patients must continue taking the medications to maintain reduced blood pressure levels and avoid complications.

Prevention

Prevention of hypertension centers on avoiding or eliminating known risk factors. Even persons at risk because of age, race, or sex or those who have an inherited risk can lower their chance of developing hypertension.

The risk of developing hypertension can be reduced by making the same changes recommended for treating hypertension:

• reducing salt intake
• reducing fat intake
• losing weight
• getting regular exercise
• quitting smoking
• reducing alcohol consumption
• managing stress

Resources

PERIODICALS

McNamara, Damian. "Obesity Behind Rise in Incidence of Primary Hypertension." Family Practice News April 1, 2003: 45-51.

McNamara, Damian. "Trial Shows Efficacy of Lifestyle Changes for BP: More Intensive Than Typical Office Visit." Family Practice News July 1, 2003: 1-2.

"New BP Guidelines Establish Diagnosis of Pre-hypertension: Level Seeks to Identify At-risk Individuals Early." Case Management Advisor July 2003: S1.

"New Hypertension Guidelines: JNC-7." Clinical Cardiology Alert July 2003: 54-63.

ORGANIZATIONS

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. 〈http://www.americanheart.org〉.

National Heart, Lung and Blood Institute. PO Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. 〈http://www.nhlbi.nih.gov〉.

Texas Heart Institute. Heart Information Service. PO Box 20345, Houston, TX 77225-0345. 〈http://www.tmc.edu/thi〉.

KEY TERMS

Arteries— Blood vessels that carry blood to organs and other tissues of the body.

Arteriosclerosis— Hardening and thickening of artery walls.

Cushing's syndrome— A disorder in which too much of the adrenal hormone, cortisol, is produced; it may be caused by a pituitary or adrenal gland tumor.

Diastolic blood pressure— Blood pressure when the heart is resting between beats.

Hypertension— High blood pressure.

Renal artery stenosis— Disorder in which the arteries that supply blood to the kidneys constrict.

Sphygmomanometer— An instrument used to measure blood pressure.

Systolic blood pressure— Blood pressure when the heart contracts (beats).

Vasodilator— Any drug that relaxes blood vessel walls.

Ventricle— One of the two lower chambers of the heart.