Systolic Blood Pressure. The systolic pressure (the first and higher number) is the force that blood exerts on the artery walls as the heart contracts to pump out the blood. High systolic pressure is a greater risk factor than diastolic pressure for brain, heart, kidney, and circulatory complications and for death, particularly in middle-aged and elderly adults.

Diastolic Blood Pressure. The diastolic pressure (the second and lower number) is the measurement of force as the heart relaxes to allow the blood to flow into the heart. High diastolic pressure is a strong predictor of heart attack and stroke in young adults.

Pulse Pressure. Pulse pressure is the difference between the systolic and the diastolic readings. It indicates stiffness and inflammation in the blood-vessel walls. The greater the difference between systolic and diastolic numbers, the greater the risk to health.

Click the icon to see an animation about blood pressure.

Hypertension Categories

There are a number of ways to categorize or describe hypertension.

• Essential Hypertension. Essential hypertension is also known as primary or idiopathic hypertension. About 90% of all high blood pressure cases are this type. The causes of essential hypertension are unknown but are based on complex processes in all major organs and systems, including the heart, blood vessels, nerves, hormones, and the kidneys.
• Secondary Hypertension. Secondary hypertension comprises about 5% of high blood pressure cases. In this condition, the cause has been identified.

Other doctors categorize hypertension based on what portion of the blood pressure reading is abnormal:

• Isolated Systolic Hypertension. Elevated systolic pressure may pose a significant danger for heart problems and stroke even when diastolic is normal -- a condition called isolated systolic hypertension. This occurs when systolic hypertension is over 140 mm Hg but diastolic pressure is normal. It is related to arteriosclerosis (hardening of the arteries). Isolated systolic hypertension is the most common form of hypertension in people older than age 50.

Click the icon to see an image of atherosclerosis.

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Review Date: 04/06/2010
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)