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High Blood Pressure (Hypertension)

What is High Blood Pressure?

Last modified: 
16/04/2013 - 13:13

Contributing Author: Guy Slowik FRCS

When you have your blood pressure taken, your health care provider is measuring the pressure, or tension, that blood exerts on the walls of the blood vessels as it travels around the body. In a healthy person, this pressure is just enough for the blood to reach all the cells of the body, but not so much that it strains blood vessel walls.

Blood pressure is measured in millimeters of mercury (mm Hg).

  • A typical normal blood pressure is 120/80 mm Hg, or "120 over 80."
  • The first number represents the pressure when the heart contracts.
  • The second number represents the pressure when the heart relaxes.
  • Blood pressure greater than 140/90 mm Hg is considered high.

Generally, blood pressure will go up at certain times - for instance, if you smoke a cigarette, win the lottery, or witness a car crash - and will return to normal when the stressful or exciting event has passed.

But when blood pressure is high all the time, the continuous increased force on blood vessel walls can damage blood vessels and organs, including the heart, kidneys, eyes, and brain.

The medical term for high blood pressure is hypertension.

Need to Know:

Systolic and Diastolic Blood Pressure

Blood travels through blood vessels much like water through a garden hose. The blood in the vessels is under pressure just like the water in a hose when the tap is turned on.

With each heartbeat more blood is pumped into the vessels - like turning up the tap - so the pressure rises. This is the systolic blood pressure, the first number in the blood pressure measurement, which is normally around 120.

Between heartbeats, while the heart is resting, the pressure in the arteries is lower. This is the diastolic pressure, second number in the blood pressure measurement, which is normally around 80.

You can increase the pressure in a hose either by turning up the tap or by putting a crimp in the hose (that is, by narrowing the hose). In this same way, the blood pressure in blood vessels will rise if fluid flows more forcefully or if the arteries are narrowed.

Pressure in a hose can be regulated either by controlling the rate at which fluid passes through it or by widening it. Likewise, the pressure in the blood vessels can be controlled, with medications that act on the heart or blood vessels and with certain lifestyle modifications.

Need to Know:

  • Although high blood pressure can be extremely dangerous, it usually causes no symptoms - so many people don't even realize they have it. High blood pressure can only be detected with accurate and repeated measurements of a person's blood pressure. That's one reason why it's so important to have regular medical checkups.
  • Even though high blood pressure can be treated safely and effectively, only about one-quarter of people who have high blood pressure take the necessary steps to keep their blood pressure within a normal range.

There are three types of hypertension:

  • Primary hypertension (essential hypertension). This is high blood pressure for which no cause can be found. Most people with high blood pressure (90 to 95 percent) have this type of hypertension. Doctors suspect that a combination of lifestyle, diet, heredity, age, gender, race/ethnicity, hormone levels, and other factors all contribute to high blood pressure.
  • Secondary hypertension (non-essential hypertension). This is high blood pressure for which a definite cause can be found. This type of high blood pressure accounts for only 5 to 10 percent of all cases of hypertension. Some of these causes are temporary or controllable - for instance, pregnancy or the use of certain medications - while others are chronic conditions like hormonal diseases, kidney disease, or head injuries.
  • Isolated systolic hypertension (ISH). Older people are sometimes susceptible to another form of high blood pressure, called isolated systolic hypertension. In people with this condition, blood pressure is higher than normal when the heart beats, but returns to normal in between beats of the heart. The large difference in pressure can place additional strain on artery walls.

Nice To Know:

Q. If I do not feel any symptoms, is there still a problem?

A. Most people with high blood pressure do not experience any symptoms. The presence of symptoms, such as headache or blurry vision, usually indicates severe or long-standing hypertension. However, over time, uncontrolled high blood pressure causes significant damage to important organs including the heart, kidneys, brain, and eyes. In a number of cases, this damage can lead to death. This is why high blood pressure is sometimes referred to as "the silent killer."

Facts about high blood pressure

  • High blood pressure is a condition in which the pressure, or tension, that blood exerts on the walls of blood vessels goes up and stays high, which can damage the blood vessels, the heart, and other organs.
  • More than 73 million Americans have high blood pressure.
  • High blood pressure is one of the most serious health problems in the United States; yet, because high blood pressure has no symptoms, millions of people with the condition do not even know they have it.
  • As many as one in four adults in the United States has high blood pressure.
  • High blood pressure affects people of all ages, racial and ethnic groups, and walks of life.
  • Doctors do not know what causes high blood pressure in 90 to 95 percent of people who have it.
  • High blood pressure is one of the most important risk factors for coronary heart disease.
  • High blood pressure is the most important risk factor for stroke, which is the third leading cause of death in the United States.
  • High blood pressure is a common cause of heart failure, the leading cause of death in the United States
  • High blood pressure is a common cause of kidney disease.

 

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High Blood Pressure (Hypertension)

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.