Blood Pressure

Index:

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What is blood pressure?  [Index]

Blood pressure results from two forces.  One is created by the heart as it pumps blood into the arteries and through the circulatory system.  The other is the force of the arteries as they resist the blood flow.

 

What do blood pressure numbers indicate?  [Index]

The systolic pressure is always stated first and the diastolic pressure second.  For example:  122/76 (122 over 76);
systolic = 122, diastolic = 76.

Blood pressure of less than 140 over 90 is considered a normal reading for adults.  A systolic pressure of 130 to 139 or a diastolic pressure of 85 to 89 needs to be watched carefully.  A blood pressure reading equal to or greater than 140 over 90 is considered elevated or high.

High Blood Pressure  [Index]

High blood pressure, or hypertension, is defined in an adult as a systolic pressure of 140 mm Hg or higher and a diastolic pressure of 90 mm Hg or higher.  Blood pressure is measured in millimeters of mercury (mm Hg).

Blood pressure (mm Hg) Optimal Normal High
Normal
Hypertension

Systolic
(top number)

less than
120
less than
130
130-139 140 or higher
Diastolic
(bottom number)
less than
80
less than
85
85-89 90 or higher

High blood pressure directly increases the risk of coronary heart disease (which leads to heart attack) and stroke, especially along with other risk factors.

High blood pressure can occur in children or adults, but it's particularly prevalent in African Americans, middle-aged and elderly people, obese people, heavy drinkers and women taking oral contraceptives.  People with diabetes mellitus, gout or kidney disease have a higher frequency of hypertension.

High blood pressure usually has no specific symptoms and no early warning signs.  It's truly a "silent killer."  But a simple, quick, painless test can detect it.

 

High Blood Pressure Causes  [Index]

In 90-95 percent of cases, the cause is unknown.  This type of high blood pressure is called essential hypertension or hardening of the arteries, thickening or hypertrophy of the artery wall, and excess contraction of the arterioles.

In the remaining cases, high blood pressure is a symptom of a recognizable underlying problem such as a kidney abnormality, tumor of the adrenal gland or congenital defect of the aorta.  When the root cause is corrected, blood pressure usually returns to normal.  This type of high blood pressure is called secondary hypertension.

 

Factors that Contribute to High Blood Pressure   [Index]

What factors increase the chance that a person will develop high blood pressure?

How do salt and sodium affect high blood pressure?

Most Americans consume far more salt (sodium) than their bodies need.  Heavy sodium consumption increases blood pressure in some people, leading to high blood pressure.  People diagnosed with high blood pressure are often put on sodium-restricted diets.

How does being overweight affect high blood pressure?

Studies have shown that body weight, changes in body weight over time, and skinfold thickness are related to changes in blood pressure levels.  These factors have been linked to the later rise and development of high blood pressure.  People who are overweight are more likely to have high-normal to mild high blood pressure.

What other related factors contribute to high blood pressure?

Background

Because medical science doesn't understand why most cases of high blood pressure occur, it's hard to say how to prevent it.  Still, several factors may contribute to it.   Being obese or overweight or using too much salt (in sodium-sensitive people) are two avoidable factors.  Drinking too much alcohol and an inactive lifestyle are two others.

People with diabetes mellitus, gout or kidney disease have a higher frequency of hypertension.

Increasing age is one risk factor that can't be changed.  Generally speaking, the older people get, the more likely they are to develop high blood pressure.

Heredity is another factor.  People whose parents have high blood pressure are more likely to develop it than those whose parents don't.  African Americans are also more likely to have high blood pressure than whites are.

The incidence of high blood pressure isn't directly related to a person's sex.   However, doctors usually keep a close watch on a woman's blood pressure during pregnancy or if she's taking oral contraceptives.  Some women who've never had high blood pressure develop it during pregnancy.  Similarly, a woman taking oral contraceptives is more likely to develop high blood pressure if she's overweight, has had high blood pressure during pregnancy, has a family history of high blood pressure or has mild kidney disease.

Some other medications also can raise blood pressure and/or interfere with the effectiveness of antihypertensive drugs.  People with high blood pressure should tell their doctor all of the prescribed and over-the-counter medicines they're taking. These include such drugs as steroids, nonsteroidal anti-inflammatory drugs (NSAIDs), nasal decongestants and other cold remedies, diet pills, cyclosporine, erythroprotein, tricyclic antidepressants, and monoamine oxidase inhibitors.

 

Why is high blood pressure harmful?  [Index]

Elevated blood pressure causes the heart to work harder than normal.  That means both the heart and arteries are more prone to injury.   High blood pressure increases the risk of heart attacks, strokes, kidney failure, damage to the eyes, congestive heart failure and atherosclerosis.  When high blood pressure exists with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack or stroke increases several times.

If high blood pressure isn't treated, the heart may have to work harder and harder to pump enough blood and oxygen to the body's organs and tissues to meet their needs.  When the heart is forced to work harder than normal for an extended time, it tends to enlarge and weaken.  A slightly enlarged heart may work well, but one that's significantly enlarged has a hard time meeting the demands put on it.

Arteries (AR'ter-eez) and arterioles also suffer the effects of elevated blood pressure.  Over time they become scarred, hardened and less elastic.  This may occur as people age, but elevated blood pressure accelerates this process, probably because hypertension speeds atherosclerosis.

Arterial damage is bad because hardened or narrowed arteries may not be able to supply the amount of blood the body's organs need.  And if the body's organs don't get enough oxygen and nutrients, they can't work properly.   Another risk is that a blood clot may lodge in an artery narrowed by atherosclerosis, depriving part of the body of its normal blood supply.

 

What can be done about high blood pressure?  [Index]

How does medicine help control high blood pressure?

Many medications, known as antihypertensives, are available to lower high blood pressure.  Some, called diuretics, rid the body of excess fluids and salt (sodium).  Others, called beta blockers, reduce the heart rate and the heart's output of blood.

Another class of antihypertensives is called sympathetic nerve inhibitors.  Sympathetic nerves go from the brain to all parts of the body, including the arteries.  They can cause the arteries to constrict, raising blood pressure.   This class of drugs reduces blood pressure by inhibiting these nerves from constricting blood vessels.

Yet another group of drugs is the vasodilators.  These can cause the muscle in the walls of the blood vessels (especially the arterioles) to relax, allowing the vessel to dilate (widen).

Other classes of drugs used to treat high blood pressure are the angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor blockers and the calcium antagonists (calcium channel blockers).  The ACE inhibitors interfere with the body's production of angiotensin, a chemical that causes that arteries to constrict, and the angiotensin II receptor blockers block the effects of angiotensin.  The calcium antagonists can reduce the heart rate and relax blood vessels.

In most cases these drugs lower blood pressure.  Quite often, however, people respond very differently to these medications.  That's why most patients must go through a trial period to find out which medications work best with the fewest side effects.

American Heart Association (AHA) Recommendation

People with high blood pressure should remember these key points:

What about diet and lifestyle changes?

Dietary and lifestyle changes also may help control high blood pressure.   Before drugs are prescribed, these methods are often recommended for people with only mildly elevated blood pressure.

The AHA Nutrition Committee has stated that to maximize the beneficial effects of diet on blood pressure,

Such diets are rich in potassium, calcium, magnesium and protein, and low in total fat, saturated fat and cholesterol.  Some people with mild hypertension can lower their blood pressure by reducing sodium (salt) in their diet.  This means avoiding salty foods and cutting down on the amount of salt used in cooking and at the table.

Excessive alcohol intake (more than two ounces of pure alcohol or two drinks per day) raises blood pressure in some people and should be restricted.   Alcoholic drinks are high in non-nutritious calories, so if you're trying to lose weight, avoid them.

Statistics show that many people who have high blood pressure are also overweight.  If you're overweight or have gained weight over time, you'll be advised to cut down on calories and lose weight.  Your doctor can prescribe a diet that's right for you.  If you're given a diet, follow it closely, including any recommendations about reducing your consumption of alcohol.  Often when people lose weight, their blood pressure drops, too.

Physical inactivity is a risk factor for heart disease.  In addition, a sedentary or inactive lifestyle tends to contribute to obesity, a risk factor for both high blood pressure and heart disease.  Regular exercise helps control weight and lower blood pressure.  Don't be afraid to be active - exercise should definitely be part of your daily program.  Besides helping to reduce your risk of heart attack, it can also help you lose weight or maintain a healthy weight.

For some people, weight loss, sodium reduction and other lifestyle changes won't lower high blood pressure as much as it needs to be lowered.  If that's your situation, you'll probably need to take medication.

 

What about low blood pressure?  [Index]

Within certain limits, the lower your blood pressure reading is, the better.  In most people, blood pressure isn't too low until it produces symptoms, such as lightheadedness or fainting.  In certain disease states, it's possible for blood pressure to be too low.  Examples include

Optimal blood pressure with respect to cardiovascular risk is less than 120/80 mm Hg.  However, unusually low readings should be evaluated to rule out medical causes.


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Material taken from the American Heart Association.