Conditions InDepth: Hypertension
The Cardiovascular System
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
Over time, high blood pressure can damage organs and tissues. It also increases the risk of coronary heart disease,
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.
High blood pressure. American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=2114. Accessed June 18, 2009.
High blood pressure. National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health/dci/Diseases/Hbp/HBP_WhatIs.html. Updated November 2008. Accessed June 18, 2009.
High blood pressure statistics. American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4621. Accessed June 18, 2009.
Last reviewed June 2009 by
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