High Blood Pressure (Hypertension)

High blood pressure, or hypertension, occurs when excessive force is exerted against artery walls as the heart pumps blood. This silent disease has no symptoms until it has reached an advanced and dangerous stage, at which point it may produce headaches, dizziness, ringing in the ears, and a rapid heart beat. If uncontrolled, hypertension can lead to a heart attack, stroke, or kidney failure. It can also damage the eyes and other organs.

In most people, the cause is unknown and the hypertension is classified as primary, or essential. In about 5 percent of cases, it may result from kidney disease, a hormonal imbalance, or some other identifiable factor. This is known as secondary hypertension.

Predisposing risk factors have been identified. These include obesity and a family history of hypertension or stroke at an early age. A high-salt diet contributes to the condition in genetically susceptible people. African-Americans have a higher incidence of hypertension than whites. Women are less prone than men to high blood pressure, but pregnancy and use of oral contraceptives increase their risk. The disease affects an estimated 50 million Americans.

Diagnostic Studies and Procedures

Because there usually are no symptoms, hypertension is most often diagnosed during a routine medical examination or a special screening program. Blood pressure is normally measured with a sphygmomanometer. This device consists of an inflatable cuff, an air pump, and a column of mercury. The cuff is wrapped around the upper arm and inflated.

The objective is to measure the amount of pressure needed to stop the flow of blood through an artery. As the air pressure in the cuff increases, it drives up the column of mercury. By listening through a stethoscope placed over the artery at a point below the cuff, a doctor or nurse can quickly determine when the flow of blood has stopped. The cuff is then decompressed, and the height of the mercury at the first thumping sound is noted. This is the systolic pressure, which is the peak force exerted against the artery wall when the heart contracts to push blood out. More pressure is released from the cuff, and a different sound is heard. This is the diastolic pressure, which occurs when the heart muscle relaxes to allow blood from the veins to flow in. Thus, in a blood pressure reading of 120/80, the 120 represents systolic pressure and 80 is diastolic pressure.

During the course of a day, blood pressure varies considerably. It is generally lowest during sleep and highest in the early morning. Anger or stress sends blood pressure up. Caffeine, nicotine, and alcohol can do so also raise blood pressure. A resting blood pressure of 120/80 is considered normal for adults. A consistent reading of 140/90 or higher is classified as hypertension. To make a diagnosis, however, blood pressure should be measured a number of times over several weeks, unless the initial reading is dangerously high -- 160/110, for example. Wearing a 24-hour blood pressure monitor may be recommended in some cases. This device continually measures and records blood pressure. If a complication related to hypertension, such as an enlarged heart, is suspected, additional tests, including a chest X-ray and electrocardiogram, may be done.

Medical Treatments

The choice of treatment is determined by the severity of the disease and the presence of complications. Mild to moderate hypertension, generally defined as readings of 140-149/90-104, is initially treated by lifestyle changes.

Antihypertensive drugs are prescribed when lifestyle changes fail to achieve the desired lowering or when blood pressure is diagnosed in the moderate to severe range of more than 160/105. Although high blood pressure almost always can be controlled, there is no single antihypertensive drug that works for everyone.

Treatment may involve taking one or several medications. The classes of antihypertensive drugs are as follows: Diuretics, also called water pills, work by increasing excretion of sodium and water through the kidneys, thereby reducing the total volume of blood. Thiazide diuretics such as hydrochlorothiazide are most commonly used, but in some cases, loop diuretics, such as furosemide (Lasix), are prescribed. These drugs work in a part of the kidney called the loop of Henle and they are generally more potent than thiazide diuretics. Both types of drugs can cause such side effects as lethargy, dizziness, and urinary frequency. Beta blockers lower blood pressure by slowing the heartbeat and reducing the amount of blood pumped during each beat. Propranolol (Inderal), the oldest beta blocker, is still widely used. In addition, there are at least a half-dozen newer ones, including atenolol (Tenormin), metoprolol (Lopressor), nadolol (Corgard), and timolol (Blocadren). ACE (for angiotensin converting enzyme) inhibitors lower blood pressure by blocking the production of angiotensin II, a body chemical that constricts, or narrows, blood vessels. ACE inhibitors include captopril (Capoten) and enalapril (Vasotec). Calcium-channel blockers work by preventing the entry of calcium into the muscle cells that control the arterial walls. This dilates, or opens, the blood vessels, making it easier for blood to flow through them. Drugs in this category include verapamil (Calan) and diltiazem (Cardizem). Vasodilators widen, or dilate, arteries. Hydralazine (Apresoline), the oldest antihypertensive drug, is a fast-acting vasodilator. Another member of this class is minoxidil (Loniten).

These drugs are usually prescribed along with other antihypertensives. Alpha-blocking agents work through the autonomic nervous system. They block the alpha receptors on the blood vessel walls, which, when stimulated, cause a narrowing of the vessels. Thus, they lower blood pressure by allowing the arteries to open more widely. Two examples are prazosin (Minipress) and terazosin (Hytrin). Peripheral adrenergic antagonists block the release of norepinephrine, a hormone that raises blood pressure. Reserpine, which is made from rauwolfia, an Indian herb, is the major drug in this category. It is usually prescribed in small doses and used in conjunction with a diuretic. Centrally acting drugs lower blood pressure by reducing nerve impulses from the brain. These agents include methyldopa (Aldomet), clonidine (Catapres), and guanabenz (Wytensin). They, too, are combined with other drugs, usually diuretics.

Side effects are often a problem with blood pressure medications. However, they can almost always be minimized by changing either the dosage or the medication itself. Among the common side effects are unusual tiredness, dizziness or feeling faint upon standing up, nightmares, impotence, and depression. These and any other lingering problems should be reported to a doctor as soon as possible so that the dosage can be changed or an alternative drug can be prescribed.

Alternative Therapies

Poorly controlled high blood pressure can have serious consequences. It is vital to see a doctor regularly and take any prescribed medications. Alternative therapies cannot cure the condition, but some can reduce or even eliminate the need for drugs. When using an alternative therapy, be sure to let your physician know, so medical treatment can be adjusted appropriately.

Acupuncture. Therapists may stimulate meridians for the liver and bladder, as well as certain ear points. Blood pressure should be monitored during every session, and these techniques should not be used for any patient whose blood pressure is higher than 160/100.

Biofeedback. Patients are taught to lower their heart rate and control other normally involuntary responses. This method is especially useful for reducing stress, which raises blood pressure.

Exercise Conditioning. A program of aerobic exercise designed to improve cardiovascular fitness can help to lower blood pressure. Before embarking on such a program, it may be advisable to have an exercise stress test.

Herbal Medicine. Dandelion tea or capsules may be recommended as a natural diuretic. Garlic, either natural or in capsule form, is also said to lower high blood pressure. Because licorice raises blood pressure, capsules, candy, and other products that contain the natural form should be avoided. The artificial flavoring that is used in most licorice candy in the United Stales is a safe substitute.

Homeopathy. Thyroidinum, prepared from the thyroid gland, is sometimes recommended. Nux vomica is also prescribed for intermittent hypertension. Nutrition Therapy. Mild to moderate hypertension can often be controlled through diet alone. Add minimal or no salt to your food, especially if you are salt sensitive. Use herbs for flavorings or ask your doctor about using potassium chloride as a salt substitute. Also, avoid processed foods that contain any form of sodium. Increase your consumption of vegetables, fruits, and whole-grain products, while reducing intake of red meat and other fatty foods.

Yoga and Meditation. These and other relaxation techniques can lower blood pressure. The effects tend to be temporary, so the chosen method should be practiced at least daily.

Self-Treatment

In addition to dietary adjustments, other lifestyle changes that should be incorporated into a prevention or treatment program include:

• If you smoke, stop now. Also, avoid exposure to second-hand smoke.
• Lose excess weight. Staying within 15 percent of your ideal weight is the single most effective thing you can do to control blood pressure.
• Avoid alcoholic beverages.

Other Causes of High Blood Pressure

An adrenal tumor called a pheochromocytoma produces adrenaline-like hormones that can cause very high blood pressure. A narrowing of the renal artery to the kidney can also raise blood pressure, as can pre-eclampsia, or toxemia of pregnancy, a serious complication that sometimes develops during the final trimester.