Conditions InDepth: Hypertension by Debra Wood, RN

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Hypertension is the medical term for high blood pressure. Blood pressure is the force of blood flow against the artery walls.

The Cardiovascular System

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Blood pressure measurements are read as two numbers. The higher number, called the systolic pressure, represents the pressure in the artery when the heart beats. The lower number, called the diastolic pressure, represents the pressure when the heart is at rest. Normal blood pressure is in the range of 120/80. High blood pressure, or hypertension, is defined as systolic pressure greater than 140 and/or diastolic pressure greater than 90. Blood pressure fluctuates throughout each day.

In most cases, the cause of hypertension is unknown. Genetic factors may be involved. In addition, the following conditions may cause hypertension: narrowing of the arteries, excess fluid in the blood, stronger than normal heartbeats, certain medications, or disorders of the kidneys, nervous system, or endocrine system (hormones).

Anatomy of the Heart

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Over time, high blood pressure can damage organs and tissues. It also increases the risk of coronary heart disease, stroke , and congestive heart failure , and it seems to contribute to hardening of the arteries.

According to the American Heart Association, about 73 million Americans have high blood pressure, but it's estimated that over half of these people do not have their condition under control.