high blood pressure(hypertension)

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Source: http://www.medicinenet.com/script/main/art.asp?articlekey=378

High Blood Pressure

(Hypertension)

Revising Medical Author: John P. Cunha, DO, FACOEP

Revising Medical Editor: Jay W. Marks, MD

y What is high blood pressure (hypertension)?

y How is the blood pressure measured? y How is blood pressure defined?

y Isolated systolic high blood pressure y White coat high blood pressure

y Borderline high blood pressure y What causes high blood pressure?

y What are the causes of secondary high blood pressure? y Renal (kidney) hypertension

y Adrenal gland tumors y Coarctation of the aorta y The metabolic syndrome and obesity y What are the symptoms of high blood pressure?

y How is end-organ damage assessed in the patient with high blood pressure? y How is high blood pressure treated?

y High Blood Pressure (Hypertension) At A Glance y Patient Discussions: High Blood Pressure - Effective Treatments

What is high blood pressure?

High blood pressure (HBP) or hypertension means high pressure (tension) in the arteries.

Arteries are vessels that carry blood from the pumping heart to all the tissues and organs of the body. High blood pressure does not mean excessive emotional tension, although emotional

tension and stress can temporarily increase blood pressure. Normal blood pressure is below120/80; blood pressure between 120/80 and 139/89 is called "pre-hypertension", and a blood

pressure of 140/90 or above is considered high.

The top number, the systolic blood pressure, corresponds to the pressure in the arteries as the

heart contracts and pumps blood forward into the arteries. The bottom number, the diastolic



pressure, represents the pressure in the arteries as the heart relaxes after the contraction. Thediastolic pressure reflects the lowest pressure to which the arteries are exposed.

An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart

(cardiac) disease, kidney (renal) disease, hardening of the arteries (atherosclerosis or

arteriosclerosis), eye damage, and stroke (brain damage).T

hese complications of hypertensionare often referred to as end-organ damage because damage to these organs is the end result of chronic (long duration) high blood pressure. For that reason, the diagnosis of high blood pressure

is important so efforts can be made to normalize blood pressure and prevent complications.

It was previously thought that rises in diastolic blood pressure were a more important risk factor than systolic elevations, but it is now known that in people 50 years or older systolic

hypertension represents a greater risk.

The American Heart Association estimates high blood pressure affects approximately one in

three adults in the United States - 73 million people. High blood pressure is also estimated to

affect about two million American teens and children, and the Journal of the American MedicalAssociation reports that many are under-diagnosed. Hypertension is clearly a major public health problem.



How is the blood pressure measured?

The blood pressure usually is measured with a small, portable instrument called a blood pressurecuff (sphygmomanometer ). (Sphygmo is Greek for pulse, and a manometer measures pressure.)

The blood pressure cuff consists of an air pump, a pressure gauge, and a rubber cuff. Theinstrument measures the blood pressure in units called millimeters of mercury (mm Hg).

The cuff is placed around the upper arm and inflated with an air pump to a pressure that blocks

the flow of blood in the main artery ( brachial artery) that travels through the arm. The arm isthen extended at the side of the body at the level of the heart, and the pressure of the cuff on the

arm and artery is gradually released. As the pressure in the cuff decreases, a health practitioner listens with a stethoscope over the artery at the front of the elbow. The pressure at which the

practitioner first hears a pulsation from the artery is the systolic pressure (the top number). As



the cuff pressure decreases further, the pressure at which the pulsation finally stops is thediastolic pressure (the bottom number).

How is high blood pressure defined?

Blood pressure can be affected by several factors, so it is important to standardize theenvironment when blood pressure is measured. For at least one hour before blood pressure is

taken, avoid eating, strenuous exercise (which can lower blood pressure), smoking, and caffeineintake. Other stresses may alter the blood pressure and need to be considered when blood

pressure is measured.

Even though most insurance companies consider high blood pressure to be 140/90 and higher for

the general population, these levels may not be appropriate cut-offs for all individuals. Manyexperts in the field of hypertension view blood pressure levels as a range, from lower levels to

higher levels. Such a range implies there are no clear or precise cut-off values to separate normal

blood pressure from high blood pressure.I

ndividuals with so-called pre-hypertension (defined asa blood pressure between 120/80 and 139/89) may benefit from lowering of blood pressure bylife style modification and possibly medication especially if there are other risk factors for end-

organ damage such as diabetes or kidney disease (life style changes are discussed below).

For some people, blood pressure readings lower than 140/90 may be a more appropriate normalcut-off level. For example, in certain situations, such as in patients with long duration (chronic)

kidney diseases that spill (lose) protein into the urine (proteinuria), the blood pressure is ideallykept at 130/80, or even lower. The purpose of reducing the blood pressure to this level in these

patients is to slow the progression of kidney damage. Patients with diabetes (diabetes mellitus)may also benefit from blood pressure that is maintained at a level lower than 130/80. In addition,

African Americans, who have an increased risk for developing the complications of hypertension, may decrease this risk by reducing their systolic blood pressure to less than 135

and the diastolic blood pressure to 80 mm Hg or less.

In line with the thinking that the risk of end-organ damage from high blood pressure represents acontinuum, statistical analysis reveals that beginning at a blood pressure of 115/75 the risk of

cardiovascular disease doubles with each increase in blood pressure of 20/10. This type of



analysis has led to an ongoing "rethinking" in regard to who should be treated for hypertension,and what the goals of treatment should be.

Isolated systolic high blood pressure

Remember that the systolic blood pressure is the top number in the blood pressure reading andrepresents the pressure in the arteries as the heart contracts and pumps blood into the arteries. Asystolic blood pressure that is persistently higher than 140 mm Hg is usually considered elevated,

especially when associated with an elevated diastolic pressure (over 90).

Isolated systolic hypertension, however, is defined as a systolic pressure that is above 140 mmHg with a diastolic pressure that still is below 90. This disorder primarily affects older people

and is characterized by an increased (wide) pulse pressure. The pulse pressure is the difference between the systolic and diastolic blood pressures. An elevation of the systolic pressure without

an elevation of the diastolic pressure, as in isolated systolic hypertension, therefore, increases the pulse pressure. Stiffening of the arteries contributes to this widening of the pulse pressure.

Once considered to be harmless, a high pulse pressure is now considered an important precursor or indicator of health problems and potential end-organ damage. Isolated systolic hypertension is

associated with a two to four times increased future risk of an enlarged heart, a heart attack (myocardial infarction), a stroke (brain damage), and death from heart disease or a stroke.

Clinical studies in patients with isolated systolic hypertension have indicated that a reduction insystolic blood pressure by at least 20 mm to a level below 160 mmHg reduces these increased

risks.

White coat high blood pressure

A single elevated blood pressure reading in the doctor's office can be misleading because theelevation may be only temporary. It may be caused by a patient's anxiety related to the stress of

the examination and fear that something will be wrong with his or her health. The initial visit tothe physician's office is often the cause of an artificially high blood pressure that may disappear

with repeated testing after rest and with follow-up visits and blood pressure checks. One out of four people that are thought to have mild hypertension actually may have normal blood pressure

when they are outside the physician's office. An increase in blood pressure noted only in thedoctor's office is called 'white coat hypertension.' The name suggests that the physician's white

coat induces the patient's anxiety and a brief increase in blood pressure. A diagnosis of whitecoat hypertension might imply that it is not a clinically important or dangerous finding.

However, caution is warranted in assessing white coat hypertension. An elevated blood pressure brought on by the stress and anxiety of a visit to the doctor may not necessarily always be aharmless finding since other stresses in a patient's life may also cause elevations in the blood

pressure that are not ordinarily being measured. Monitoring blood pressure at home by blood pressure cuff or continuous monitoring equipment or at a pharmacy can help estimate the

frequency and consistency of higher blood pressure readings. Additionally, conductingappropriate tests to search for any complications of hypertension can help evaluate the

significance of variable blood pressure readings.



Borderline high blood pressure

Borderline hypertension is defined as mildly elevated blood pressure higher than 140/90 mm Hg

at some times, and lower than that at other times. As in the case of white coat hypertension, patients with borderline hypertension need to have their blood pressure taken on several

occasions and their end-organ damage assessed in order to establish whether their hypertensionis significant.

People with borderline hypertension may have a tendency as they get older to develop moresustained or higher elevations of blood pressure. They have a modestly increased risk of

developing heart-related (cardiovascular) disease. Therefore, even if the hypertension does notappear to be significant initially, people with borderline hypertension should have continuing

follow-up of their blood pressure and monitoring for the complications of hypertension.

If, during the follow-up of a patient with borderline hypertension, the blood pressure becomes persistently higher than 140/ 90 mm Hg, an anti-hypertensive medication is usually started. Even

if the diastolic pressure remains at a borderline level (usually under 90 mm Hg, yet persistentlyabove 85) treatment may be started in certain circumstances.

What causes high blood pressure?

Two forms of high blood pressure have been described: essential (or primary) hypertension andsecondary hypertension. Essential hypertension is a far more common condition and accounts for

95% of hypertension. The cause of essential hypertension is multifactorial, that is, there areseveral factors whose combined effects produce hypertension. In secondary hypertension, which

accounts for 5% of hypertension, the high blood pressure is secondary to (caused by) a specificabnormality in one of the organs or systems of the body. (Secondary hypertension is discussed

further in a separate section later.)

Essential hypertension affects approximately 72 million Americans, yet its basic causes or underlying defects are not always known. Nevertheless, certain associations have been

recognized in people with essential hypertension. For example, essential hypertension developsonly in groups or societies that have a fairly high intake of salt, exceeding 5.8 grams daily. Salt

intake may be a particularly important factor in relation to essential hypertension in severalsituations, and excess salt may be involved in the hypertension that is associated with advancing

age, African American background, obesity, hereditary (genetic) susceptibility, and kidneyfailure (renal insufficiency). The Institute of Medicine of the National Academies recommends

healthy 19 to 50-year-old adults consume only 3.8 grams of salt to replace the average amount

lost daily through perspiration and to achieve a diet that provides sufficient amounts of other essential nutrients.

Genetic factors are thought to play a prominent role in the development of essentialhypertension. However, the genes for hypertension have not yet been identified. (Genes are tiny

portions of chromosomes that produce the proteins that determine the characteristics of individuals.) The current research in this area is focused on the genetic factors that affect the



renin-angiotensin-aldosterone system. This system helps to regulate blood pressure bycontrolling salt balance and the tone (state of elasticity) of the arteries.

Approximately 30% of cases of essential hypertension are attributable to genetic factors. For

example, in the United States, the incidence of high blood pressure is greater among African

Americans than among Caucasians or Asians. Also, in individuals who have one or two parentswith hypertension, high blood pressure is twice as common as in the general population. Rarely,certain unusual genetic disorders affecting the hormones of the adrenal glands may lead to

hypertension. (These identified genetic disorders are considered secondary hypertension.)

The vast majority of patients with essential hypertension have in common a particular abnormality of the arteries: an increased resistance (stiffness or lack of elasticity) in the tiny

arteries that are most distant from the heart (peripheral arteries or arterioles). The arteriolessupply oxygen-containing blood and nutrients to all of the tissues of the body. The arterioles are

connected by capillaries in the tissues to the veins (the venous system), which returns the bloodto the heart and lungs. Just what makes the peripheral arteries become stiff is not known. Yet,

this increased peripheral arteriolar stiffness is present in those individuals whose essentialhypertension is associated with genetic factors, obesity, lack of exercise, overuse of salt, and

aging. Inflammation also may play a role in hypertension since a predictor of the development of hypertension is the presence of an elevated C reactive protein level (a blood test marker of

inflammation) in some individuals.

What are the causes of secondary high blood pressure?

As mentioned previously, 5% of people with hypertension have what is called secondary

hypertension. This means that the hypertension in these individuals is secondary to (caused by) aspecific disorder of a particular organ or blood vessel, such as the kidney, adrenal gland, or aortic

artery.

Renal (kidney) hypertension

Diseases of the kidneys can cause secondary hypertension. This type of secondary hypertensionis called renal hypertension because it is caused by a problem in the kidneys. One important

cause of renal hypertension is narrowing (stenosis) of the artery that supplies blood to thekidneys (renal artery). In younger individuals, usually women, the narrowing is caused by a

thickening of the muscular wall of the arteries going to the kidney (fibromuscular hyperplasia).In older individuals, the narrowing generally is due to hard, fat-containing (atherosclerotic)

plaques that are blocking the renal artery.

How does narrowing of the renal artery cause hypertension? First, the narrowed renal arteryimpairs the circulation of blood to the affected kidney. This deprivation of blood then stimulates

the kidney to produce the hormones, renin and angiotensin. These hormones, along withaldosterone from the adrenal gland, cause a constriction and increased stiffness (resistance) in the

peripheral arteries throughout the body, which results in high blood pressure.



Renal hypertension is usually first suspected when high blood pressure is found in a youngindividual or a new onset of high blood pressure is discovered in an older person. Screening for

renal artery narrowing then may include renal isotope (radioactive) imaging, ultrasonographic(sound wave) imaging, or magnetic resonance imaging (MR I) of the renal arteries. The purpose

of these tests is to determine whether there is a restricted blood flow to the kidney and whether

angioplasty (removal of the restriction in the renal arteries) is likely to be beneficial.H

owever, if the ultrasonic assessment indicates a high resistive index within the kidney (high resistance to blood flow), angioplasty may not improve the blood pressure because chronic damage in the

kidney from long-standing hypertension already exists. If any of these tests are abnormal or thedoctor's suspicion of renal artery narrowing is high enough, renal angiography (an X-ray study in

which dye is injected into the renal artery) is done. Angiography is the ultimate test to actuallyvisualize the narrowed renal artery.

A narrowing of the renal artery may be treated by balloon angioplasty. In this procedure, the

physician threads a long narrow tube (catheter) into the renal artery. Once the catheter is there,the renal artery is widened by inflating a balloon at the end of the catheter and placing a

permanent stent (a device that stretches the narrowing) in the artery at the site of the narrowing.This procedure usually results in an improved blood flow to the kidneys and lower blood

pressure. Moreover, the procedure also preserves the function of the kidney that was partiallydeprived of its normal blood supply. Only rarely is surgery needed these days to open up the

narrowing of the renal artery.

Any of the other types of chronic kidney disease that reduces the function of the kidneys can alsocause hypertension due to hormonal disturbances and/or retention of salt.

It is important to remember that not only can kidney disease cause hypertension, buthypertension can also cause kidney disease. Therefore, all patients with high blood pressure

should be evaluated for the presence of kidney disease so they can be treated appropriately.

Adrenal gland tumors

Two rare types of tumors of the adrenal glands are less common, secondary causes of hypertension. The adrenal glands sit right on top of the kidneys. Both of these tumors produce

excessive amounts of adrenal hormones that cause high blood pressure. These tumors can bediagnosed from blood tests, urine tests, and imaging studies of the adrenal glands. Surgery is

often required to remove these tumors or the adrenal gland (adrenalectomy), which usuallyrelieves the hypertension.

One of the types of adrenal tumors causes a condition that is called primary hyperaldosteronism because the tumor produces excessive amounts of the hormone aldosterone. In addition to thehypertension, this condition causes the loss of excessive amounts of potassium from the body

into the urine, which results in a low level of potassium in the blood. Hyperaldosteronism isgenerally first suspected in a person with hypertension when low potassium is also found in the

blood. (Also, certain rare genetic disorders affecting the hormones of the adrenal gland can causesecondary hypertension.)



The other type of adrenal tumor that can cause secondary hypertension is called a pheochromocytoma. This tumor produces excessive catecholamines, which include several

adrenaline-related hormones. The diagnosis of a pheochromocytoma is suspected in individualswho have sudden and recurrent episodes of hypertension that are associated with flushing of the

skin, rapid heart beating ( palpitations), and sweating, in addition to the symptoms associated

with high blood pressure.

Coarctation of the aorta

Coarctation of the aorta is a rare hereditary disorder that is one of the most common causes of

hypertension in children. This condition is characterized by a narrowing of a segment of theaorta, the main large artery coming from the heart. The aorta delivers blood to the arteries that

supply all of the body's organs, including the kidneys.

The narrowed segment (coarctation) of the aorta generally occurs above the renal arteries, whichcauses a reduced blood flow to the kidneys. This lack of blood to the kidneys prompts the renin-

angiotensin-aldosterone hormonal system to elevate the blood pressure. Treatment of thecoarctation is usually the surgical correction of the narrowed segment of the aorta. Sometimes,

balloon angioplasty (as described above for renal artery stenosis) can be used to widen (dilate)the coarctation of the aorta.

The metabolic syndrome and obesity

Genetic factors play a role in the constellation of findings that make up the "metabolicsyndrome." Individuals with the metabolic syndrome have insulin resistance and a tendency to

have type 2 diabetes mellitus (non-insulin-dependent diabetes).

Obesity, especially associated with a marked increase in abdominal girth, leads to high bloodsugar (hyperglycemia), elevated blood lipids (fats), vascular inflammation, endothelial

dysfunction (abnormal reactivity of the blood vessels), and hypertension all leading to prematureatherosclerotic vascular disease. The American Obesity Association states the risk of developing

hypertension is five to six times greater in obese Americans, age 20 to 45, compared to non-obese individuals of the same age. The American Journal of Clinical Nutrition reported in 2005

that waist size was a better predictor of a person's blood pressure than body mass index (BMI).Men should strive for a waist size of 35 inches or under and women 33 inches or under. The

epidemic of obesity in the United States contributes to hypertension in children, adolescents, andadults.

What are the symptoms of high blood pressure?

Uncomplicated high blood pressure usually occurs without any symptoms (silently) and so

hypertension has been labeled "the silent killer." It is called this because the disease can progressto finally develop any one or more of the several potentially fatal complications of hypertension

such as heart attacks or strokes. Uncomplicated hypertension may be present and remainunnoticed for many years, or even decades. This happens when there are no symptoms, and those

affected fail to undergo periodic blood pressure screening.



Some people with uncomplicated hypertension, however, may experience symptoms such asheadache, dizziness, shortness of breath, and blurred vision. The presence of symptoms can be a

good thing in that they can prompt people to consult a doctor for treatment and make them morecompliant in taking their medications. Often, however, a person's first contact with a physician

may be after significant damage to the end-organs has occurred. In many cases, a person visits or

is brought to the doctor or an emergency room with a heart attack , stroke, kidney failure, or impaired vision (due to damage to the back part of the retina). Greater public awareness andfrequent blood pressure screening may help to identify patients with undiagnosed high blood

pressure before significant complications have developed.

About one out of every 100 (1%) people with hypertension is diagnosed with severe high blood pressure (accelerated or malignant hypertension) at their first visit to the doctor. In these patients,

the diastolic blood pressure (the minimum pressure) exceeds 140 mm Hg! Affected persons oftenexperience severe headache, nausea, visual symptoms, dizziness, and sometimes kidney failure.

Malignant hypertension is a medical emergency and requires urgent treatment to prevent a stroke(brain damage).

How is end-organ damage assessed in the patient with high blood pressure?

Damage of organs fed by the circulatory system due to uncontrolled hypertension is called end-

organ damage. As already mentioned, chronic high blood pressure can lead to an enlarged heart,kidney failure, brain or neurological damage, and changes in the retina at the back of the eyes.

Examination of the eyes in patients with severe hypertension may reveal damage; narrowing of the small arteries, small hemorrhages (leaking of blood) in the retina, and swelling of the eye

nerve. From the amount of damage, the doctor can gauge the severity of the hypertension.

People with high blood pressure have an increased stiffness, or resistance, in the peripheral

arteries throughout the tissues of the body.T

his increased resistance causes the heart muscle towork harder to pump the blood through these blood vessels. The increased workload can put a

strain on the heart, which can lead to heart abnormalities that are usually first seen as enlargedheart muscle. Enlargement of the heart can be evaluated by chest X-ray, electrocardiogram, and

most accurately by echocardiography (an ultrasound examination of the heart).Echocardiography is especially useful in determining the thickness (enlargement) of the left side

(the main pumping side) of the heart. Heart enlargement may be a forerunner of heart failure,coronary (heart) artery disease, and abnormal heart rate or rhythms (cardiac arrhythmias). Proper

treatment of the high blood pressure and its complications can reverse some of these heartabnormalities.

Blood and urine tests may be helpful in detecting kidney abnormalities in people with high blood pressure. (Remember that kidney damage can be the cause or the result of hypertension.)

Measuring the serum creatinine in a blood test can assess how well the kidneys are functioning.

An elevated level of serum creatinine indicates damage to the kidney. In addition, the presenceof protein in the urine (proteinuria) may reflect chronic kidney damage from hypertension, even

if the kidney function (as represented by the blood creatinine level) is normal. Protein in theurine alone signals the risk of deterioration in kidney function if the blood pressure is not

controlled. Even small amounts of protein (microalbuminuria) may be a signal of impending



y Several classes of anti-hypertensive medications are available, including ACE inhibitors,AR B drugs, beta-blockers, diuretics, calcium channel blockers, alpha-blockers, and

peripheral vasodilators.

y Most antihypertensive medications can be used alone or in combination: some are used

only in combination; some are preferred over others in certain specific medical situations;and some are not to be used (contraindicated) in other situations.

y The goal of therapy for hypertension is to bring the blood pressure down to 140/85 in thegeneral population and to even lower levels in diabetics, African Americans, and people

with certain chronic kidney diseases.

y Screening, diagnosing, treating, and controlling hypertension early in its course can

significantly reduce the risk of developing strokes, heart attacks, or kidney failure.

Previous contributing author, Dwight Makoff, MD

Last Editorial Review: 8/10/2010

© 2010 MedicineNet, Inc. All rights reserved.MedicineNet does not provide medical advice, diagnosis or treatment. See

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