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You are here : 3-RX.com > Medical Encyclopedia > Diseases and Conditions > High Blood Pressure
      Category : Health Centers > High Blood Pressure

High Blood Pressure

Alternate Names : Hypertension

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

Blood pressure is expressed in millimeters of mercury, or mm Hg. High blood pressure is defined as a systolic blood pressure reading greater than 140 mm Hg or a diastolic blood pressure reading greater than 90 mm Hg. The systolic blood pressure is the top number of a blood pressure reading. This shows the maximum pressure in the blood vessels. Pressure is highest as the heart contracts and circulates blood throughout the body. The diastolic blood pressure is the bottom number of a blood pressure reading. It shows the lowest pressure in the blood vessels. Pressure is lowest between heartbeats, when the heart is at rest.

The National Institutes of Health has further defined high blood pressure. These categories are for people 18 years and older who do not take medication for high blood pressure and do not have a short-term serious illness. These categories are as follows.

  • Normal blood pressure is a systolic blood pressure of less than 130, and a diastolic pressure of less than 85.
  • High normal blood pressure is a systolic blood pressure of 130 to 139, and a diastolic pressure of 85 to 89.
  • Stage 1 high blood pressure is a systolic blood pressure of 140 to 159, and a diastolic pressure of 90 to 99.
  • Stage 2 high blood pressure is a systolic blood pressure of 160 to 179, and a diastolic pressure of 100 to 109.
  • Stage 3 high blood pressure is a systolic blood pressure of 180 or higher, or a diastolic blood pressure of 110 or higher.
  • What is going on in the body?

    The heart, blood vessels, brain, and kidneys control blood pressure. Blood pressure is also controlled by the amount of fluid and salt in the body. Certain hormones in the body can affect both blood vessels and body fluids. The force of the contraction of the heart can also affect blood pressure.

    In most people who have high blood pressure, the cause is unknown. In this case, high blood pressure is called primary, or essential, hypertension.

    What are the causes and risks of the condition?

    Ninety to 95% of the time, high blood pressure is labeled as essential hypertension. This means that the cause is unknown. The American Heart Association has identified both controllable and noncontrollable risk factors for high blood pressure.

    Uncontrollable risk factors for high blood pressure include age, heredity, and race. In men, high blood pressure occurs most often between 35 and 50 years of age. In women, it generally starts after menopause. An individual is more likely to develop high blood pressure if his or her parents or close relatives have it. Certain races have a higher incidence of high blood pressure. For example, African Americans develop high blood pressure earlier and more often than Caucasians.

    Controllable risk factors for high blood pressure include the following:

  • diet high in sodium
  • excess or frequent consumption of alcohol
  • lack of exercise
  • obesity
  • smoking
  • stress that is not well-managed
  • Secondary high blood pressure is caused by one of the following conditions:

  • acute lead poisoning
  • alcohol abuse
  • cocaine and other illegal drugs
  • congenital heart disease, such as coarctation of the aorta
  • hormonal abnormalities, such as a hyperactive condition of the adrenal glands known as Cushing's syndrome
  • injury or radiation therapy to the kidneys
  • kidney disease, such as glomerulonephritis and polycystic kidney disease
  • medications, such as corticosteroids
  • oral contraceptives, or birth control pills
  • pregnancy with preeclampsia
  • tumors of the adrenal gland, such as a pheochromocytoma

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    Next section

       

    High Blood Pressure: Symptoms & Signs

    Author: Bill Harrison, MD
    Reviewer: Eileen McLaughlin, RN, BSN
    Date Reviewed: 08/09/01



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