Hypertension: High Blood Pressure

Nearly one in three adults has hypertension or high blood pressure, according to the National Heart, Lung, and Blood Institute (NHLBI). Many don't know it, though, because high blood pressure often produces no symptoms. But even if there are no symptoms, untreated high blood pressure can damage internal organs, so it's important to be aware of your risks.

What is blood pressure

Every time your heart beats, it pushes blood into your arteries, creating pressure in them. (Read about "The Heart & Cardiovascular System") This is what keeps blood moving through your body. (Read about "Vascular System") According to NHLBI, most of us have probably had our blood pressure measured at some point, using what's called a sphygmomanometer. (Read about a sphygmomanometer in "Cardiovascular Tests")

A blood pressure cuff is wrapped around your upper arm and inflated to stop the blood flow in your artery for a few seconds. A valve is opened and air is then released from the cuff so the blood can start flowing again. The sounds of your blood rushing through an artery are heard through a stethoscope.

The first sound heard and registered on the gauge or mercury column is called the systolic blood pressure. This is the maximum pressure in the artery produced as the heart contracts and the blood begins to flow again.

The last sound heard as more air is released from the cuff is the diastolic blood pressure. This is the lowest pressure that remains within the artery when the heart is at rest. The two readings are given, one (systolic) over the other (diastolic) in millimeters (mm) of mercury (Hg), such as 120/80 mmHg. Here are the categories for blood pressure measurements in adults:

• Normal - For the average healthy adult, NHLBI says a normal systolic level is under 120 mmHg and a normal diastolic level is under 80 mmHg.
• Prehypertension - For otherwise healthy adults, NHLBI says that if your systolic number is 120-139, or your diastolic number is 80-89, you have prehypertension. This means that you don't have high blood pressure now but are likely to develop it in the future. You can take steps to improve your high blood pressure by adopting a healthy lifestyle.
• Hypertension - If you are an otherwise healthy adult, and your systolic number is higher than 139 or your diastolic number is higher than 89, you have high blood pressure. High blood pressure is further divided into categories:
  • Stage 1 hypertension - For an otherwise healthy adult, a systolic number of 140-159 or a diastolic number of 90-99 is considered stage 1 hypertension.
  • Stage 2 hypertension - For an otherwise healthy adult, a systolic number over 160 or a diastolic number over 100 is considered stage 2 hypertension.

Your systolic and diastolic numbers may not be in the same blood pressure category. In this case, the more severe category is the one you're in. For example, if your systolic number is 130 and your diastolic number is 75, your would still be considered to have prehypertension. According to NHLBI, for persons middle aged and older, systolic pressure gives a better diagnosis of high blood pressure. For younger people, the diastolic blood pressure is an important hypertension number.

If you have diabetes or chronic kidney disease, HBP is defined as 130/80 mmHg or higher. (Read about "Diabetes" "Kidney Disease")

HBP numbers also differ for children and teens. To find out whether a child has HBP, a doctor will compare the child's blood pressure numbers to average numbers for his or her age, height, and gender.

Although high blood pressure (also called hypertension) may not produce any symptoms you can feel, it still causes damage, which is why it's often called the "silent killer." Left untreated, high blood pressure can damage your blood vessels, as well as internal organs such as your heart or kidneys. (Read about "Enlarged Heart" "Blood Pressure and Kidney Disease") Having high blood pressure also means you have a higher risk of developing heart disease or having a stroke. (Read about "Coronary Heart Disease" "Stroke") In addition, NHLBI says studies show that even high-normal blood pressure puts you at an increased risk of disease. The only way to find out if your blood pressure is too high is to have it measured by a healthcare professional.

Risk factors

According to the American Medical Association (AMA), we don't know exactly what causes high blood pressure, but there are certain things that can put you at a higher risk of having high blood pressure. Some you can control; others you can't. They include:

• Family and personal medical history - If a close relative has high blood pressure, you yourself may have a higher risk. If you have diabetes or kidney disease, if you smoke, or if you're a woman who's pregnant, you may also face a higher risk. (Read about "Diabetes" "Healthy Pregnancy")
• Age - In general, as we get older, our risk of developing high blood pressure increases.
• Race - African-Americans have a higher risk of developing high blood pressure.
• Obesity - Excess weight increases your risk of high blood pressure. (Read about "Obesity")
• Lifestyle - If you don't get much exercise, you're at a higher risk of having high blood pressure. Drinking too much alcohol can also raise blood pressure. (Read about "Alcoholism")

In addition, the American Heart Association (AHA) says that in certain sodium-sensitive people, using too much salt may contribute to high blood pressure. (Read about "Sodium") Certain medications can also raise blood pressure, according to AHA; therefore, anyone with high blood pressure should make sure they tell their doctor about any prescribed and/or over-the-counter medicines they're taking, such as steroids, nonsteroidal anti-inflammatory drugs (NSAIDs), nasal decongestants and other cold remedies, diet pills, antidepressants, and monoamine oxidase inhibitors.

AHA recommends a blood pressure screening by a healthcare professional at least once every two years. If a screening reveals elevated blood pressure, your doctor will decide on the appropriate follow-up and treatment.

Treatment options

Sometimes, high blood pressure can be controlled through changes in lifestyle and diet, cutting back on salt or sodium for example, or losing weight. (Read about "Low Fat Food Tips") A special diet, called DASH for Dietary Approaches to Stop Hypertension, was developed by NHLBI. Basically, the DASH diet is low in saturated fat, cholesterol and total fat and emphasizes fruits, vegetables and low fat dairy foods. The DASH diet is also low in red meat, sweets and sugar-containing drinks. It is rich in potassium, calcium, magnesium, fiber and protein. (Read about "Vitamins & Minerals" "Calcium") NHLBI says this special diet has been found to lower blood pressure, especially when people also reduce their sodium intake much lower than the currently recommended maximum of 2,400 milligrams a day. (Read about "Dietary Guidelines") Exercise is often suggested for people with high blood pressure. (Read about "Exercise and Your Heart") Be sure to check with your doctor before beginning any exercise program.

Your doctor may decide, however, that (along with diet and lifestyle changes) medication is needed as well. There are a number of different types or classes of medications to control hypertension. According to NHLBI, they include:

• Beta-blockers - These reduce nerve impulses to the heart and blood vessels. They are designed to make the heart beat less often and with less force, so that blood pressure drops and the heart doesn't work as hard.
• Angiotensin converting enzyme (ACE) inhibitors - These prevent the formation of a hormone called angiotensin II, which normally causes vessels to narrow. They are designed to make the blood vessels relax so that pressure goes down.
• Angiotensin II receptor antagonists also called angiotensin receptor blockers (ARBs) - These shield blood vessels from angiotensin II (the hormone that causes vessels to narrow). As a result, the vessels are wider and pressure lowers.
• Calcium channel blockers (CCBs) - These keep calcium from entering the muscle cells of the heart and blood vessels, so that blood vessels relax and pressure goes down.
• Diuretics - These are sometimes called "water pills" because they work in the kidney and flush excess water and sodium from the body through urine. (Read about "The Urinary System") This reduces the amount of fluid in the blood. And, since sodium is flushed out of blood vessel walls, the vessels open wider. Pressure goes down. There are different types of diuretics. They are often used with other high blood pressure drugs.
• Alpha blockers - Alpha blockers reduce nerve impulses to blood vessels. That allows blood to pass more easily, causing the blood pressure to go down. According to results from an NHLBI clinical study, an alpha blocker may not be the best choice for initial treatment for uncomplicated high blood pressure.
• Alpha-beta blockers - Alpha-beta blockers work the same way as alpha blockers but also slow the heartbeat, as beta blockers do. As a result, less blood is pumped through the vessels and the blood pressure goes down.
• Nervous system inhibitors - Nervous system inhibitors relax blood vessels by controlling nerve impulses. This causes the blood vessels to become wider and the blood pressure to go down. (Read about "Nervous System")
• Vasodilators - Vasodilators directly open blood vessels by relaxing the muscle in the vessel walls, causing the blood pressure to go down.
• Renin inhibitor - Renin is a kidney enzyme associated with blood pressure regulation. The Food and Drug Administration says a renin inhibitor should not be used during pregnancy. (Read about "Healthy Pregnancy")

One thing antihypertensives have in common is that they may have side effects. They may also interact with other medications you take, both prescription and over-the-counter. (Read about "Drug Interaction Precautions" "Herbal Precautions") Therefore, it's important for your doctor and pharmacist to be aware of any other medications you may be using.

AHA says different people respond in different ways to these medications. Therefore, most patients must go through a trial period to find out which medications work best with the least number of side effects. When taking medication, any side effects should be reported to your doctor, but patients should not decide to stop taking the medicine without their doctor's advice. (Read about "Medicine Safety")

Pulmonary hypertension

There is another type of hypertension called pulmonary hypertension (PH). (Read about "Pulmonary Hypertension") It affects the lungs and the pulmonary artery. Pulmonary hypertension happens when the blood pressure in the pulmonary artery rises far above normal levels. The pulmonary artery is the blood vessel carrying oxygen-poor blood from the right ventricle, one of the pumping chambers of the heart, to the lungs. (Read about "Vascular System") In the lungs, the blood picks up oxygen and then flows to the left side of the heart, where it is pumped by the left ventricle to the rest of the body through the aorta.

Normal mean pulmonary-artery pressure is approximately 14 mm Hg at rest. In the PH patient, the mean blood pressure in the pulmonary artery is greater than 25 mm Hg at rest and 30 mm Hg during exercise. This abnormally high pressure (pulmonary hypertension) is associated with changes in the small blood vessels in the lungs, resulting in an increased resistance to blood flowing through the vessels. This increased resistance, in turn, places a strain on the right ventricle, which now has to work harder than usual against the resistance to move adequate amounts of blood through the lungs.

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