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high blood pressure

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Sphygmomanometer (Blood Pressure Meter)

Alternative Names

High blood pressure, or hypertension, is defined as a systolic blood pressure reading greater than 140 or a diastolic blood pressure reading greater than 90. The systolic blood pressure is the top number of a blood pressure reading. This shows the force of the contraction of the heart and the tone or condition of the blood vessels. The diastolic blood pressure is the bottom number of a blood pressure reading. It shows the pressure in the blood vessels between heartbeats.

What is going on in the body?
The heart, blood vessels, brain, and kidneys control blood pressure. Blood pressure is also controlled by the amount of fluid and salt in the body. Certain hormones in the body can affect both blood vessels and body fluids. The force of the contraction of the heart can also affect blood pressure.

When the top blood pressure number is over 140 or the lower number is over 90 for long periods of time, a person is considered to have high blood pressure. In most people with high blood pressure, the cause is unknown. In this case, high blood pressure is called essential hypertension.

What are the signs and symptoms of the condition?
Often, a person will have high blood pressure without any symptoms. Over time, however, a person may develop: The main sign of high blood pressure is an elevated systolic or diastolic blood pressure. Generally a blood pressure of 120/80 is considered normal. Blood pressure tends to rise with stress or exercise. It should return to normal when the person is at rest.

What are the causes and risks of the condition?
In 90% to 95% of people diagnosed with high blood pressure, the cause is unknown. In some cases, high blood pressure is caused by kidney, heart, or hormone problems. Some medications and excessive alcohol use can also cause high blood pressure.

What can be done to prevent the condition?
Maintaining a healthy body weight, including physical activity in everyday life, and eating a diet designed to minimise heart disease can help prevent high blood pressure. However, research findings have shown that high blood pressure caused by job stress in women, does not go away outside of the work setting. Even with lifestyle changes, many cases of high blood pressure cannot be prevented. If there is a medical cause of high blood pressure, treatment of the underlying condition can help prevent hypertension.

How is the condition diagnosed?
The diagnosis of hypertension is made on the basis of many blood pressure readings. High blood pressure is diagnosed if several repeat readings show a systolic blood pressure over 140 or a diastolic blood pressure over 90. Blood tests and other tests may also be done to make sure there is not an obvious cause for the high blood pressure.

What are the long-term effects of the condition?
Uncontrolled high blood pressure can lead to many serious long-term effects. Damage can occur in the brain, kidneys, and heart. There can also be blood vessel damage to the eye. High blood pressure can lead to stroke, heart attack, or arteriosclerosis, which is hardening of the arteries.

High blood pressure can also lead to chronic renal failure, a form of kidney failure requiring dialysis to filter body fluids. Enlargement of the heart and problems with arrhythmias, or irregular heartbeats, can be caused by uncontrolled high blood pressure.

What are the risks to others?
High blood pressure is not contagious and does not pose a risk to others.

What are the treatments for the condition?
If the high blood pressure is caused by another condition, treating that underlying condition may bring the blood pressure down. There are many medications that are used to treat high blood pressure, including:
  • diuretics, such as hydrochlorothiazide/triamterene
  • beta-blockers, such as propranolol or atenolol
  • angiotensin-converting enzyme (ACE) inhibitors, such as lisinopril
  • angiotensin II receptor blockers, such as losartan or valsartan
  • vasodilators, such as hydralazine
  • centrally acting nervous system medications, such as clonidine
Calcium channel blockers, such as diltiazem, nifedipine, or verapamil, have been used for over 20 years to treat high blood pressure. However, the findings of 2 recent studies have shown that people who take a calcium channel blocker have a much higher incidence of complications than people taking other medications for high blood pressure. One study, for example, found that the risk of heart attack was 27% greater, and the risk of congestive heart failure was 26% higher.

The choice of medication varies depending on a person's medical history. Beta-blockers usually are avoided in someone with breathing problems such as asthma or emphysema. ACE inhibitors and diuretics to reduce fluid buildup are especially useful for an individual with kidney disease or diabetes. A person who has high blood pressure may be on multiple medications.

The goal of treatment is to keep the top number below 140 and the bottom number below 90. In a person with diabetes, the goal is to keep the top number below 130 and the bottom number below 85. For an individual with heart disease or kidney disease, the goal is to get the blood pressure as low as can be tolerated.

What are the side effects of the treatments?
The side effects of treatment of high blood pressure vary according to the medications used. Beta-blockers can worsen asthma. Diuretics can cause dehydration and salt imbalance. Calcium channel blockers can cause swelling of the legs, as well as a higher risk of heart attack and congestive heart failure. ACE inhibitors may lead to chronic dry cough.

What happens after treatment for the condition?
A person who has high blood pressure needs to continue to take the prescribed medications daily. Blood pressure may return to normal as a result of weight loss, increased physical activity, reduction of alcohol intake, and a diet low in sodium. In most cases, a person will need to continue to take blood pressure medications for life.

How is the condition monitored?
High blood pressure is monitored through frequent visits to a doctor. A person who has high blood pressure often records blood pressure readings between doctor visits. Any new or worsening symptoms should be reported to the doctor.

Author: Bill Harrison, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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