Hypertension

Hypertension (high blood pressure) is a condition in which a person's blood pressure is elevated.
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About high blood pressure

High blood pressure (hypertension) is a condition in which a person’s blood pressure is elevated. Blood pressure is the measure of the force of the blood pushing against the walls of the arteries – the blood vessels that carry blood from the heart to the rest of the body. If the high blood pressure has no known cause (more than 90 percent of causes), it is known as primary, essential or idiopathic hypertension. If it is caused by another condition, such as kidney disease, it is known as secondary hypertension. However, because of the complex variety of systems that influences blood pressure, these distinctions have blurred somewhat in clinical practice.

Blood pressure measurement is inexpensive and easily performed. Blood pressure is measured in two phases that correspond to the natural contractions of the heart. When the heart contracts (e.g., systole), the pressure of blood against arterial walls is known as systolic pressure. When it relaxes (diastole), the pressure of blood against arterial walls is known as diastolic pressure.

High Blood Pressure

Blood pressure is always expressed as systolic pressure over diastolic pressure. Normal blood pressure for adults is considered to be below 120/80 millimeters of mercury (mm/Hg). Generally, blood pressure above 140/90 is considered to be high for adults, and blood pressure under 90/60 is considered to be low for adults (hypotension). High blood pressure may be diagnosed if any of the following three conditions is true:

A new category, prehypertension, is being used to refer to individuals with blood pressures between 120-139/80-89. Such individuals are typically not prescribed medication, but they are advised to adopt lifestyle modifications to help keep blood pressure from rising. Lifestyle modifications might include weight loss, diet, exercise, reducing salt intake and quitting smoking.

Although the cause of most cases of high blood pressure is unknown, researchers have uncovered intriguing evidence that blood pressure is associated with insulin resistance and/or elevated insulin levels (hyperinsulinemia). Both high blood pressure and insulin resistance are features of the metabolic syndrome, a cluster of abnormalities that includes obesity, elevated triglycerides and low HDL "good" cholesterol. A number of possible mechanisms have been proposed that would explain how insulin resistance contributes to hypertension. However, this link is still poorly understood.

Researchers have also identified dozens of genes that contribute to high blood pressure. Though this implies that some people inherit a propensity for high blood pressure, the picture is more complicated than that. Researchers believe that about 30 percent of essential hypertension can be traced back to genetic abnormalities that run in families. Most recent studies have seemed to indicate that inherited high blood pressure is the result of multiple gene expressions, and there is currently no genetic test that consistently identifies people at risk for developing high blood pressure.

Whatever its cause, high blood pressure exacts a tremendous cost from society. High blood pressure is a major risk factor for heart attack, stroke and heart failure. According to the American Heart Association, about 69 percent of people who have a first heart attack, 77 percent who have a first stroke and 74 percent who have congestive heart failure have blood pressure higher than 140/90 mm Hg. High blood pressure has also been linked to sleep apnea, which itself is associated with heart disease. Some recent research suggests that premature birth in males may result in an increased risk of high blood pressure later in life.

Before age 55, men are more likely to suffer from high blood pressure than women. After age 50, however, women experience a gradual rise in blood pressure, possibly due to the loss of hormones associated with menopause. By age 74, women are much more likely to have high blood pressure than men.

Despite its wide-ranging reach and potentially serious consequences, high blood pressure is relatively easy to diagnose and can be controlled, either with medications or lifestyle modifications. It is very important that people with high blood pressure seek treatment and follow their physician’s plan. Left untreated, high blood pressure will gradually continue to rise, causing the heart to overwork itself to the point at which serious damage can occur. Untreated high blood pressure also places other systems (e.g., circulation) and organs (e.g., the kidneys) at greater risk of damage that could lead to dysfunction or failure.

Hypertensive patients are at increased risk of:

  • Heart disease (e.g., heart failure, sudden cardiac death, cardiomyopathy) and arrhythmias.
  • Stroke
  • Accelerated coronary artery disease
  • Aortic aneurysm (a weakness in the aortic wall where it balloons out to more than 1.5 times its normal size and is in danger of rupturing), often resulting in sudden cardiac death
  • Kidney failure
  • Retinopathy (eye disease that leads to loss of vision)

Although 130/80 is considered ideal, researchers at the National Heart, Lung and Blood Institute (NHLBI) report that the risk of developing coronary artery disease can begin at blood pressures little higher than 115/75 mmHg, and that risk doubles with each 20/10 mmHg increment.

An important exception to the information listed above is noted among patients with diabetes and/or kidney disease. In these patients, hypertension is associated with an exceptionally higher rate of complications. These patients will require treatment if their blood pressure is above 130/85. Research has found success with a new drug, indapamide. For individuals with diabetes and high blood pressure, the drug was seen to lower blood pressure without affecting blood sugar

Signs and symptoms of high blood pressure

The majority of people with mild to moderate high blood pressure cannot tell when their blood pressure is too high. In fact, about one-third of hypertensive people are not aware of their condition. If symptoms are present, patients may experience chest pain (angina), shortness of breath or other symptoms related to heart disease or underlying damage. High blood pressure may cause any of the following:

  • Fatigue
  • Confusion
  • Nausea or upset stomach
  • Vision changes or problems
  • Excessive sweating
  • Paleness or redness of skin
  • Nosebleeds
  • Anxiety or nervousness
  • Strong, fast or obviously irregular heartbeat (palpitations)
  • Ringing or buzzing in ears
  • Impotence
  • Headache
  • Dizziness

Diagnosis methods for high blood pressure

The diagnosis for high blood pressure begins with the physician taking a patient’s full medical history. During the medical history, the physician will ask whether high blood pressure runs in the family and what the patient’s dietary habits have been like (e.g., salt intake). The physician will also give the patient a physical examination, which will include checking the patient’s blood pressure in both arms while standing and lying down. In some cases, the physician may ask the patient to take his or her own blood pressure at home and bring in a daily log of blood pressure measurements. This strategy will help establish the patient’s normal blood pressure pattern and rule out white coat hypertension (high blood pressure that is caused by anxiety over being in a physician’s office). It has also been shown that, in adults 65 years of age and older, blood pressure may drop somewhat in the first two hours after eating. This may result in an inaccurate blood pressure reading if taken during that interval.

Typically, blood pressure is measured by wrapping an arm cuff (attached to a sphygmomanometer) snugly around the patient’s arm and then using a stethoscope to listen to the brachial artery located at the inside elbow on the same arm. The cuff is pumped full of air until circulation is very briefly cut off. Then some air will be slowly let out of the device, loosening the cuff’s grip on the arm and releasing the blood to flow freely again. As the air is let out, the examiner watches the numbers coming down on a simple monitor (sphygmomanometer) and waits until he or she first hears the heartbeat. The number at which that occurs is the systolic pressure. The examiner remembers this as the numbers continue to come down on the monitor and notes the number at which he or she last hears the heartbeat. The number at which that occurs is the diastolic pressure. Other blood pressure measurement devices may also be used. Some use mercury manometers to measure the pressure and others employ digital readouts.

Reliable blood pressure monitors are also available for people who are interested in monitoring their own blood pressure and/or that of their family members. When purchasing these monitors, it is important to consult with a physician or a consumer product-rating agency regarding the reliability of home monitors. Generally, arm cuff digital monitors are the easiest and most reliable to use but should be periodically checked with a mercury sphygmomanometer. Researchers are also testing 24-hour blood pressure monitors, with early studies focusing on patients with high blood pressure who are at increased risk for a heart attack.

According to the American Heart Association, automated blood pressure devices found in some public areas (e.g., drug stores) should generally not be considered reliable or accurate measuring devices. These machines are often poorly maintained and can return inaccurate results for large individuals.

Also, ambulatory blood pressure monitoring has revealed that in normal individuals, blood pressure is higher during the morning hours and drops at night (also called the dipping phenomenon). The absence of normal dipping is abnormal and has been associated with increased risk of cerebral and cardiac complications in patients with and without established hypertension.

Following the physical examination, a number of tests will often be ordered, which include:

  • Urinalysis and various blood tests (e.g., electrolytes and waste products) tests to rule out kidney disease. Blood glucose testingand a complete lipid profile, including cholesterol and triglyceride levels, is also usually recommended. Other blood tests including thyroid function tests and white blood cell counts, plus calcium and phosphate levels.
  • Electrocardiogram (EKG), which measures the heart’s electrical activity. By analyzing the EKG results, a physician can check for heart-related problems that could be associated with high blood pressure (e.g., left ventricular hypertrophy), which can occur as a result of long-term, uncontrolled high blood pressure. Doppler studies can also detect abnormalities in heart relaxation (diastolic dysfunction), as a complication of hypertension.
  • Echocardiogram , which uses ultrasound waves to visualize the structures and functions of the heart. This test is also used to check for heart–related problems such as left ventricular hypertrophy

Treatment options for high blood pressure

Depending on the severity of high blood pressure, the physician may recommend lifestyle modifications, either with or without medications. In general, patients with a blood pressure reading of 140/90 or greater are candidates for medical intervention, in addition to lifestyle changes. Patients with isolated systolic hypertension (e.g., a blood pressure reading of 160/89) over the age of 65 are also candidates for medical therapy. Prehypertensive patients are generally advised to make a number of lifestyle changes before medical therapy is begun. Definite steps that should be taken to lower and control blood pressure include:

  • Quitting smoking . This is perhaps the most important thing a smoker can do to promote his or her own health. Among many other side effects, smoking elevates blood pressure. For more information, see Smoking Related Diseases, Smoking Addiction and Smoking Cessation.
  • Losing weight . Loss of weight in the abdominal area can immediately reduce blood pressure and help reduce the size of the heart. Weight loss accompanied by salt restriction may allow mild hypertensives to reduce or eliminate their need for medication. For more information, see Obesity & Heart Health and Weight Loss.
  • Following the DASH diet. Well-controlled studies have shown that people on the American Heart Association’s Dietary Approaches to Stop Hypertension diet, or “DASH” diet, for only eight weeks experienced a significant reduction in blood pressure. The DASH diet emphasizes fruits, vegetables, whole grains and low-fat dairy while limiting saturated fat and red meat. For more information or recipes, see DASH Diet or Low-Salt Recipes.
  • Getting adequate amounts of vitamins and minerals. Studies show that vitamin C protects normal levels of nitric oxide – the substance that keeps arteries flexible. Vitamin E and the B-vitamins may also be helpful. Also, adequate intake of minerals such as potassium, magnesium and calcium is thought by some experts to be even more helpful than reducing salt intake for reducing blood pressure. Individuals should consult with their physician before supplementing their diet. For more information, see Vitamins & Minerals.
  • Engaging in regular aerobic exercise. Exercising three to four times per week is helpful for regulating high blood pressure, keeping in mind that the regularity of the exercise is more important than the intensity of the workout. For example, studies have shown that tai chi (an ancient Chinese workout involving slow, relaxing movements) may lower blood pressure almost as well as moderately intense aerobics. Individuals should consult with their physician before starting an exercise program. For more information, see Benefits of Exercise for Heart Patients.
  • Limiting alcohol use to one drink per day for women and two drinks per day for men. One drink is defined as one 6-ounce glass of wine per day, one 12-ounce beer or one 1-ounce shot of distilled spirits. For more information, see Alcohol & Heart Disease.
  • Limiting salt intake to 2,000 milligrams (2 grams) per day.
  • Using stress management techniques. Emotional factors may play important roles in the development of hypertension. Studies have shown that cognitive-behavioral therapy, transcendental meditation, active religious faith and participation in church-related activities are all associated with reducing blood pressure to healthy levels (watching or listening to religious services on radio or TV had no effect).
  • Having a pet may also lower blood pressure (see Health Benefits of Pets).

Women are also encouraged to discuss with their physicians the increased risk of high blood pressure that results from taking birth control pills, particularly if they are over the age of 35. According to the American Heart Association, high blood pressure is two to three times more common in women taking birth control pills than those not taking them, especially in women who are overweight or obese.

As hypertensive patients make these changes, they are often encouraged to monitor their blood pressure at home, under the guidance of their physician. In addition to these lifestyle changes, patients are often prescribed blood pressure-reducing medications. These medications include:

  • Diuretics . Medications that promote the formation of urine in the kidneys, causing the body to flush out excess fluids and minerals, especially sodium. These are often the first medications given to reduce high blood pressure. Though commonly used, they may have unwanted side effects, such as low potassium levels (hypokalemia). This side effect can be minimized with the use of potassium-sparing diuretics.
  • Alpha blockers and beta blockers. Medications that inhibit alpha and beta receptors in various parts of the nervous system. This helps arteries to relax, decreases the force of the heartbeat and reduces blood pressure. Beta blockers are especially useful in patients with heart disease, but they should be used with caution among diabetic patients because they interfere with the body's normal responses to fluctuating glucose levels. Alpha blockers work by interfering with norepinephrine, which causes increased cardiac activity. They are not usually used as first-line therapy, however, because patients may develop a tolerance to the medication and their use has recently been implicated in an increase in cardiovascular events.
  • ACE inhibitors . These medications are vasodilators that help to reduce blood pressure by inhibiting substances in the blood that cause blood vessels to constrict. Recent studies suggest that this class of drugs may be superior to others in preventing stroke, heart disease and kidney disease in patients (especially diabetic individuals) with risk factors for vascular disease. They are also very useful in patients with established heart disease.
  • Angiotensin II receptor blockers (ARBs). This new class of drugs is showing good results and great promise in reducing complications related to high blood pressure. They have similar effects to ACE inhibitors, although they are more specific in their mode of action and have fewer side effects. Although beta blockers, ACE inhibitors and diuretics are currently used most often in the treatment of high blood pressure, ARBs may be prescribed more often in the future.
  • Calcium channel blockers . These are vasodilators that inhibit the flow of calcium into heart and blood vessel tissues, which reduces tension in the heart, relaxes blood vessels and lowers blood pressure. However, most studies have not shown that these agents reduce the risk of death from high blood pressure, and some of these medications may increase the risk of death from high blood pressure.

Though some of the newer medications have been shown to lower both blood pressure and the risks of heart disease, they had not been tested against each other until recently. This was addressed with the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). Begun in 1994, involving more than 42,000 individuals and the largest such trial to date, this important study showed that “traditional” diuretics were more effective in treating high blood pressure and should be used as first-line therapy. Participants with high blood pressure were randomly given diuretics, calcium channel blockers, ACE inhibitors or alpha blockers.

Results five years later revealed that, compared to the other classes of drugs in the study, diuretics were not only significantly more effective in lowering high blood pressure, but also in lowering the risk of cardiovascular events (e.g., stroke, angina, heart failure). In fact, the alpha blocker category was terminated in March 2000 due to a higher rate of cardiovascular events and hospitalization compared to diuretics. Based on these findings, the ALLHAT researchers concluded that drug therapy to lower blood pressure should be initiated with diuretics.

The ALLHAT researchers did recognize some limitations to the study. Commenting on the significantly lower blood pressure attained with the diuretic-controlled group (compared to calcium channel blockers and ACE inhibitors), the benefit may have been secondary to overall better blood pressure control in that group and perhaps not just from the diuretic itself. Indeed, other studies have shown a marked and significant benefit from ACE inhibitors, specifically ramipril, in reducing the progression of atherosclerosis, preventing strokes and heart attacks, and prolonging life in patients with vascular disease, high blood pressure, diabetes and heart failure.

The majority of patients with high blood pressure will need to take medications for the rest of their lives in order to control the condition. In some cases, two or three antihypertensives may be given. Recent studies have shown that such a combination of drugs not only lowers blood pressure but also may reduce the risk of stroke and ischemic heart disease. Other research has suggested that some patients with only slightly elevated blood pressures may eventually be able to stop taking medications and control their condition through lifestyle changes alone. The two most important lifestyle changes tracked by the study were weight loss and maintaining a low-salt diet. Strategies such as exercise, diet plans and, especially, changes in drugs should be discussed with a physician before they are attempted.

Researchers have also been exploring the genetic roots of high blood pressure. Identifying genes that cause high blood pressure in a particular patient could help physicians to prescribe the most effective antihypertensive drug