High Blood Pressure

High blood pressure, also called hypertension, is, simply, elevated pressure of the blood in the arteries. Hypertension results from two major factors, which can be present independently or together:

• The heart pumps blood with excessive force.
• The body's smaller blood vessels (known as the arterioles) narrow, so that blood flow exerts more pressure against the vessels' walls.

Although the body can tolerate increased blood pressure for months and even years, eventually the heart may enlarge (a condition called hypertrophy), which is a major factor in heart failure. Such pressure can also injure blood vessels in the heart, kidneys, the brain, and the eyes.

Two numbers are used to describe blood pressure: the systolic pressure (the higher and first number) and the diastolic pressure (the lower and second number). Health dangers from blood pressure may vary among different age groups and depending on whether systolic or diastolic pressure (or both) is elevated. A third measurement, pulse pressure, is becoming important as an indicator of severity.

Blood pressure is measured in millimeters of mercury (mm Hg). For example, excellent blood pressure would be less than 120/80 mm Hg (systolic/diastolic). Blood pressure is now categorized as optimal, normal, high normal, and hypertensive. The hypertensive category is further divided, according to severity. [See Table Blood Pressure and Its Treatments.]

American expert groups recommend that any blood pressure above normal should be treated. Some experts are concerned, however, that such guidelines may unnecessarily increase the use of anti?hypertensive drugs.

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 now known to be a greater risk factor than diastolic pressure for heart, kidney, and circulatory complications and for death, particularly in middle?aged and elderly adults. The wider the spread between the systolic and diastolic measurements, the greater the danger.

In fact, elevated systolic pressure may pose a significant danger for heart events and stroke events even when diastolic is normal ?? a condition called isolated systolic hypertension. Isolated systolic hypertension is the most common form of hypertension in people older than fifty. In one study it comprised 87% of hypertension cases in people between ages 50 and 59.

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

Pulse Pressure. Pulse pressure is the difference between the systolic and the diastolic readings. It appears to be an indicator of stiffness and inflammation in the blood?vessel walls. The greater the difference between systolic and diastolic numbers, the stiffer and more injured the vessels are thought to be. Although not yet used by physicians to determine treatment, evidence is suggesting that it may prove to be a strong predictor of heart problems, particularly in older adults. Some studies suggest that in people over 45 years old, every 10?mm Hg increase in pulse pressure increases the risk for stroke increases by 11%, cardiovascular disease by 10%, and overall mortality by 16%. (In
younger adults the risks are even higher.)

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