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What Is High Blood Pressure?

Blood pressure is the amount of force exerted by the blood as it moves against the vessel walls, and is carefully regulated by the body. It depends on the volume of your blood and the stiffness or elasticity of your blood vessels.1

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High blood pressure is often called the "silent killer" because it usually has no symptoms. High blood pressure can cause permanent changes to your blood vessels and heart that may cause serious problems elsewhere in your body:1-3

  1. Changes in your blood vessels: Over time, the increased force of blood pumping against your vessels causes them to become harder and narrower.
  2. Excess stress on the heart: High blood pressure makes the heart work harder than it should.

Lowering blood pressure may help avoid permanent changes to your blood vessels and heart.

How high is too high?

Blood pressure is measured using a cuff that goes around your upper arm. The cuff is inflated, and then as the air is let out your doctor or nurse listens to your pulse with a stethoscope. Systolic blood pressure is measured when your doctor or nurse first hears your pulse. Diastolic pressure is measured when he or she can no longer hear your pulse. Some doctors and nurses use an electronic device to measure blood pressure.

Blood pressure is usually written as systolic over diastolic (eg, 120/80).1 The top (or first) number is the systolic number (and is always higher), and the bottom (or second) number is the diastolic number. Blood pressure numbers are sometimes followed by the notation "mm Hg." This stands for millimeters of mercury, and is the unit of measure used in a blood pressure gauge.

Are there any symptoms of high blood pressure?

When you have high blood pressure, you may not feel sick or look sick.4 Make no mistake about it though: high blood pressure can eventually cause serious problems with your heart and/or other organs.5

Next: the causes of high blood pressure

References

1. Sherwood L. The blood vessels and blood pressure. In: Sherwood L, ed. Human Physiology: From Cells to Systems. 3rd ed. Belmont, Calif: Wadsworth; 1997:305-51.

2. Kaplan NM. Systemic hypertension: mechanisms and diagnosis. In: Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald’s Heart Disease. 7th ed. Philadelphia, Pa: Elsevier Saunders; 2005:959-87.

3. Your guide to lowering high blood pressure. National Heart, Lung, and Blood Institute. Available at: http://www.nhlbi.nih.gov/hbp/hbp/intro.htm. Accessed August 8, 2008.

4. National Heart, Lung, and Blood Institute. How Do I Know If I Have High Blood Pressure? Available at: http://www.nhlbi.nih.gov/hbp/detect/know.htm. Accessed May 28, 2008.

5. National Heart, Lung, and Blood Institute. Why Is High Blood Pressure Important? Available at: http://www.nhlbi.nih.gov/hbp/hbp/serious.htm. Accessed May 28, 2008.


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