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Hypertension Health Article

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Definition

Hypertension is high blood pressure. Blood pressure is the force of blood pushing against the walls of arteries as it flows through them.

Description

As blood flows through arteries it pushes against the inside of the artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure will be. The size of small arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls narrow, or constrict.

Blood pressure is highest when the heart beats to pump blood out into the arteries. Between beats, when the heart relaxes to refill with blood, the pressure drops to its lowest point. The blood pressure peak, when the heart pumps, is called systolic pressure. The blood pressure trough, when the heart is filling, is called diastolic pressure. When blood pressure is measured, the systolic pressure is stated first and the diastolic pressure second. Blood pressure is measured in millimeters of mercury (mm Hg). For example, if a person's systolic pressure is 120 and diastolic pressure is 80, it is written as 120/80 mm Hg. The American Heart Association considers systolic blood pressure less than 140 and diastolic blood pressure less than 90 normal for adults.

Hypertension is a significant public health problem. Since it has no symptoms, many people are unaware that they have hypertension. In the United States, about 50 million people age six and older have high blood pressure. Hypertension occurs more frequently in men than women and in people over the age of 65 than in younger persons. More than half of all Americans over the age of 65 have hypertension. It is also more prevalent in African-Americans than in white Americans.

Hypertension is serious because it places patients at higher risk for heart disease and other medical problems than people with normal blood pressure. Serious complications may be prevented by encouraging patients to check their blood pressure regularly, and by treating hypertension once it is diagnosed.

If left untreated, hypertension can lead to the following medical conditions:

arteriosclerosis, also called atherosclerosis
myocardial infarction (heart attack)
cerebrovascular accident (stroke)
left ventricular hypertrophy leading to congestive heart failure
chronic renal failure (kidney damage)

Arteriosclerosis is hardening of the arteries. The walls of arteries have a layer of muscle and elastic tissue that makes them flexible and able to dilate and constrict as needed. High blood pressure can cause artery walls to thicken and harden. When artery walls thicken, the lumen (hollow center of the blood vessel) narrows. Cholesterol and fatty plaques are more likely to build up on the walls of damaged arteries, further narrowing them. Blood clots can also become trapped in narrowed arteries, blocking the flow of blood.

Arteries narrowed by arteriosclerosis may restrict blood flow to organs and other tissues. Reduced or blocked blood flow to the heart can cause myocardial infarction (a heart attack). Similarly, if an artery to the brain is blocked, a stroke can result.

Hypertension forces the heart muscle to work harder to pump blood through the body. The extra workload can cause the heart muscle to thicken and stretch. When the heart becomes too enlarged, it cannot pump enough blood. If hypertension continues and is not treated, the heart may fail.

The kidneys remove waste from the blood. Chronic hypertension thickens the arteries to the kidneys and impairs renal (kidney) function. As the condition progresses, the kidneys eventually fail and hemodialysis or kidney transplant will be needed. About 25% of people who receive hemodialysis have kidney failure caused by hypertension.

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