High blood pressure, or hypertension, increases your chances of developing heart disease or kidney disease and of having a stroke. About one in every four American adults has high blood pressure but may not be aware of it. It is often called “the silent killer” because it usually causes no symptoms. However, high blood pressure is easy to diagnose, and there are practical steps you can take to bring your blood pressure under control. Blood pressure is the force of blood pushing against the walls of the arteries that carry blood throughout your body. It is measured in millimeters of mercury, or mm Hg, using an instrument called a sphygmomanometer (pronounced sfig'mo-mah-nom'e-ter). Blood pressure is highest when the heart contracts (beats) and pumps blood into the arteries. This is called the systolic pressure. Between beats, when the heart is resting, the pressure falls. This is called the diastolic pressure. A blood pressure reading is always given as a combination of these two pressures; the high (systolic) pressure is written above or before the low (diastolic) pressure. For example, if your blood pressure reading is 120 over 70, it is written as 120/70 mm Hg; 120 is the systolic pressure, and 70 is the diastolic pressure.
Different activities make your blood pressure rise or fall. For example, normally, blood pressure rises when you are exercising and falls when you are resting. A blood pressure reading of 140/90 mm Hg or lower is generally considered normal. High blood pressure is classified according to guidelines that reflect the levels at which blood pressure begins to pose significant health risks. The guidelines for classifying blood pressure are shown in the following table:
A diagnosis of high blood pressure is based on two or more blood pressure readings taken at separate visits to the doctor’s office. If your systolic pressure falls into one category and your diastolic pressure into another, the higher reading will be used to classify your blood pressure. For example, a blood pressure of 160/90 mm Hg would be classified as stage II. A reading of 170/120 mm Hg would be classified as stage III. Because diastolic pressure represents the lower and more constant level of pressure in the arteries, physicians may emphasize it more, especially in younger people. However, the systolic blood pressure is more important for determining the risk of heart attack or stroke. People with high blood pressure have elevated blood pressure most of the time. Their blood is pushing against the walls of their arteries with higher than normal force. If left untreated, high blood pressure can lead to:
• Atherosclerosis. Uncontrolled high blood pressure causes the artery walls to thicken and lose elasticity. This encourages formation of fatty deposits on the artery wall, which narrow the channel and interfere with blood flow throughout
the body. In time, atherosclerosis can lead to a heart attack or a stroke.
• Enlarged heart. High blood pressure causes the heart to work harder. Over time this causes the heart muscle to thicken and stretch. The heart becomes less efficient and has to work harder and harder to pump blood throughout the body. Eventually this can result in heart failure.
• Kidney damage. The kidneys act as filters to rid the body of wastes. Over a number of years, high blood pressure can narrow and thicken the blood vessels of the kidneys. The kidneys then filter less blood, and waste builds up in the bloodstream. This could lead to kidney failure. When kidney failure occurs, dialysis (a technique to remove waste products from the blood and excess fluids from the body) or a kidney transplant may be necessary.
• Stroke. High blood pressure can weaken the walls of the arteries or cause them to thicken. A weakened artery wall in the brain could break, causing a hemorrhage. If a blood clot blocks one of the narrowed arteries, a stroke may occur. In most cases, the cause or causes of high blood pressure are unknown. This type is known as primary or essential hypertension. Primary hypertension cannot be cured, but it can be controlled. Secondary hypertension is caused by, or is “secondary” to, another disease. For example, some cases of high blood pressure can be traced to tumors of the adrenal gland, chronic kidney disease, or hormone abnormalities. Secondary hypertension can be cured by treating its underlying cause.
