Hypertension is the medical term for high blood pressure. Blood pressure is the measure of force that blood flow creates against the artery walls. High blood pressure is when this pressure is higher than expected.

Normal blood pressure is in the range of 120/80 millimeters of mercury (mmHg). The higher number, called the systolic, represents the pressure in the artery when the heart beats. The lower number, called the diastolic, represents the pressure when the heart is at rest. .

The American Heart Association (AHA) uses the following blood pressure categories:

  • Blood pressure is considered elevated, but not yet hypertension (abnormally high blood pressure) when the:
    • Systolic pressure is 120-129 mmHg and the
    • Diastolic pressure is 80 mmHg
  • Stage 1 hypertension:
    • Systolic pressure is 130-139 mmHg and/or
    • Diastolic pressure is 80-89 mmHg
  • Stage 2 hypertension:
    • Systolic pressure is greater than or equal to 140 mmHg and/or
    • Diastolic pressure is greater than or equal to 90 mmHg

There are 2 main types of hypertension:

  • Primary—hypertension without any known cause, most common cause
  • Secondary—hypertension with a known or underlying cause

The Cardiovascular System

The Cardiovascular System
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Causes

The blood vessels throughout the body are designed to help blood flow smoothly, direct blood flow where necessary, and help to manage blood pressure. High blood pressure may occur because of one or more of the following:

  • Damage to the walls of the blood vessels that make it difficult for blood to flow through
  • Build up of plaque (atherosclerosis) or blood clots on blood vessel walls that reduce the area the blood can pass through
  • Structural problems with blood vessels—from congenital conditions
  • Conditions or medication that make blood vessels tighten when they should not
  • Decreased elasticity of blood vessels—common effect of aging

These conditions make it harder for the heart to push blood throughout the body. The heart has to push harder for each heart beat and the blood flow can become more turbulent, which both increase pressure on the blood vessel walls.

Primary blood pressure often develops over time because of a combination of these factors.

Secondary hypertension on the other hand, usually develops more quickly and is caused by other health conditions, such as kidney or endocrine disorders, or sleep apnea. Over-the-counter and prescription medications can also cause secondary hypertension.