World Hypertension Day, 17 May 2014

Hypertension (high blood pressure) is one of the leading causes of heart attack, stroke, kidney failure and premature death.

Description

Your blood pressure is the force exerted by your heart, against the resistance created by the arteries, to keep blood flowing through your body. Your blood pressure is high (hypertension) when the force is excessive.

A blood pressure measurement is made up of two parts: systolic and diastolic. Systolic pressure occurs in arteries during heart contraction, and diastolic pressure during the period of heart relaxation between beats. This is why a blood pressure measurement is expressed as one figure "over" another, for example 140/90 mm Hg. The measurement unit, millimetre mercury (symbol Hg), is derived from the distance that a column of mercury in the measurement instrument is pressed upward.

The following table shows the normal ranges of blood pressure and the stages of hypertension for South Africans. High normal blood pressure requires more regular monitoring. Stage 1 is less severe than Stage 3.

Blood Pressure	Systolic (mm Hg)	Diastolic (mm Hg)
NORMAL RANGE
Optimal	120 or less	80 or less
Normal	Less than 130	Less than 85
High normal	130 -139	85 - 89
HYPERTENSION
Stage 1	140 - 159	90 - 99
Stage 2	160 - 179	100 - 109
Stage 3	180 or higher	110 or higher

This represents an arbitrary decided upon level of blood pressure above which the advantages of treatment is more than the disadvantages.

Hypertension is diagnosed when blood pressure measurements are above either of these normal levels on two or more separate occasions.

Elevated blood pressure readings may not always indicate that a person has hypertension, as in the case of White coat hypertension - high readings caused by a natural alerting response during blood pressure measurement (the emotional stress of having a clinician take your blood pressure).

Cause

There are two types of hypertension, namely primary and secondary hypertension.

Primary hypertension

More than 90% of hypertension cases have no known or identifiable cause. This type of hypertension is called primary or essential hypertension.

Secondary hypertension

In some cases, another disease or a medication may cause hypertension. This is called secondary hypertension. Treating the underlying cause can sometimes cure this type of hypertension. Secondary hypertension may be caused by:

• Kidney problems - these account for a large percentage of secondary hypertension. Normally the kidneys play an important role in fluid and blood pressure control.
• Coarctation of the aorta - an inborn, abnormal narrowing of the primary blood vessel supplying blood to the body from the heart
• Prescription and non-prescription drug usage
• Recreational drug usage - ecstacy and cocaine can cause hypertensive crisis and death
• Excessive alcohol intake - implicated in about 10% of secondary hypertension
• Sleep apnoea - Research indicates a connection between obstructed breathing during sleep and hypertension. The effect persists during the waking hours.
• Pheochromocytoma - a tumour of the adrenal gland (secretes various hormones, including those that affect blood pressure)
• Thyroid dysfunction - both over- and under-performance (hypo- and hyperthyroidism)
• Cushing's syndrome and aldosteronism - disorders of the outer layer of the adrenal gland resulting in various hormonal imbalances.

If hypertension occurs with any of the following factors, it may indicate that the hypertension is secondary:

• Age below 35
• Abrupt onset
• Lack of family history of essential hypertension
• Severity (180/110 mm Hg or higher)
• History of blood vessel disease, such as blockages in arteries in the neck or heart (carotid or coronary arteries)
• Lack of response to usual drug treatment
• Sudden increase of blood pressure that has been controlled by medications (provided you did not stop taking your medications)

Symptoms

Under the heading "Common Hypertension Symptoms", an author of a medical text left the entire page blank - he was emphasising the absence of symptoms seen in most people with hypertension.

Hypertension can go undetected for years, damaging your tissues and vital organs. Essential hypertension rarely has any symptoms. Most people with hypertension feel fine (are asymptomatic) and only learn of their hypertension during a routine examination or an examination for some other problem. You could be one of these people. Sometimes people who have been diagnosed with hypertension report headaches, dizziness, fatigue, and pounding of the heart. These symptoms may be related to hypertension.

More advanced cases of hypertension, especially rapidly increasing (malignant) hypertension, may cause:

• Headaches, especially pulsating headaches behind the eyes
• Visual disturbances
• Nausea and vomiting
• Disturbed levels of consciousness such as sleepiness and even seizures in severe cases

Once complications have set in, related symptoms may be present, such as chest pain from coronary artery disease.

Prevalence

About a quarter of American adults have hypertension. About one-third of these people are unaware that they have the condition.

The number of people with hypertension increases with age in both men and women.

• Hypertension is uncommon before the age of 20.
• Men are more likely to develop hypertension before the age of 50 than women are.

Course

If you have hypertension, your heart works harder than it should to pump blood to distant tissues and organs. If this pressure isn't controlled, your heart enlarges and your arteries become scarred, hardened and less flexible. Eventually, your overworked heart may not be able to pump and transport blood properly through stiff arteries.

These changes increase the risk of:

• Heart disease such as heart attacks (myocardial infarction, or the death of heart muscle)
• Heart failure (failure to pump enough blood to your body's tissues and organs to meet their needs)
• Stroke
• Kidney failure
• Peripheral vascular disease (any abnormal condition arising in the blood vessels outside the heart)

The risk of complications increases along with increase in blood pressure, i.e. there is not an abrupt cut-off point above which complications appear. Treatment and follow-up recommendations will depend on factors such as the severity of the hypertension and whether other organs, such as the kidneys, have been affected by it. Organ damage can occur if systolic, diastolic or both blood pressures are high.

Hypertension can damage blood vessels that supply blood to the light-sensitive lining of the back of the eye (the retina). This damage, retinopathy, can lead to vision loss or blindness if untreated.

Hypertension doesn't have to be deadly. It's easy to diagnose and once you know you have it, it can be controlled. Many experts believe that improved detection, treatment and control of hypertension is a major reason why there has been a 50% decrease in death due to heart disease and a 57% decrease in death caused by stroke in America in the last 20 years.

Risk factors

Risk factors for essential hypertension include:

• Family history of hypertension
• Increased age
• Black ethnicity
• Sensitivity to sodium (salt) intake
• Excessive alcohol consumption
• Low intake of potassium, magnesium and calcium
• Obesity
• Physical inactivity

People with hypertension are at increased risk of developing complications if the following associated factors are present:

• Cigarette smoking
• High cholesterol levels
• Diabetes
• Family history of early coronary artery disease in a parent or sibling (before age 45 for men or 55 for women)
• Male sex
• Black ethnicity

When to see a doctor

Contact your nearest emergency service or general practitioner immediately if you suffer from hypertension and during home monitoring:

• Your blood pressure is 180/110 mm Hg or higher.
• You have a sudden, severe headache, especially if associated with a hypertension reading.

Call a health professional if:

• Your blood pressure is higher than 130/85 mmHg on two or more occasions. Adults are encouraged to have their blood pressure checked regularly.
• You have had one high blood pressure measurement - the professional should take another reading to verify the first one. (Many doctors' offices, clinics or pharmacies will take blood pressure measurements free of charge and without an appointment.)
• You develop significant side effects from any medication taken for hypertension.

Diagnosis

Have a health care provider check your blood pressure annually. This will ensure accuracy. He or she will measure the pressure of blood in your arteries and detect subtle sounds when your heart contracts and between beats. (Results from automated screening tests such as coin-operated machines are often inaccurate.)

Hypertension is diagnosed only after several careful measurements show that the systolic and/or diastolic blood pressure is consistently above normal. This is because normal blood pressure fluctuates and stressful situations, such as a visit to your doctor's rooms, can elevate your blood pressure temporarily. Hypertension can be diagnosed after one reading, if this reveals extreme hypertension. In most cases, an extensive work-up is not needed to diagnose hypertension.

The following tests are performed to diagnose hypertension and related conditions:

1. Routine investigations

• Physical examination and medical history - confirms the presence of hypertension and determines its severity, evaluates possible damage to organs, establishes the presence of associated diseases that increase the risk of complications and looks for possible causes of secondary hypertension. The doctor will look into your eyes with a special instrument to assess possible damage to the retina.
• Creatinine, blood urea nitrogen and potassium test - a blood test that indicates how well the kidneys are functioning and whether they are damaged.
• Urine analysis - abnormalities, such as the presence of blood and protein, give an indication of kidney damage and may suggest that the kidneys are also involved in causing secondary hypertension.
• Blood glucose (fasting) - can indicate the presence of diabetes, which increases the risk of complications.
• Serum cholesterol - diagnoses high cholesterol, which adds to the risk of complications in the hypertensive patient.
• Electrocar diogram (ECG) - a recording of the electrical activity of the heart, which indicates the degree of damage to the heart and detects previous heart attacks.

If there is reason to suspect that blood pressure measurements taken in the doctor's rooms do not represent a true blood pressure (for example, as a result of white coat hypertension), or if there are large fluctuations in blood pressure, out-of-office blood pressure monitoring over 24 hours may be needed. This can take the form of self-monitoring at home or continuous ambulatory blood pressure monitoring.

The 24 hour monitor is now considered a highly accurate and reproducible investigation and predicts outcome far more accurately than office blood pressure. It is not routinely advised but used for special situations. It must be remembered that a daytime mean blood equivalent to office 140/90 is 128/83.

2. Special tests to detect organ damage

Other tests may be done to determine if hypertension has caused damage to the heart or kidneys, or if the person has had a stroke:

• Chest X-ray - shows the heart's size and presence of fluid in the lungs.
• Echocardiogram - a live image of the heart and its contractions on a television screen.
• CAT or MRI scans - computerised axial tomography or magnetic resonance imaging can show damaged brain tissue in a patient who has had a stroke.

3. Tests to detect causes of secondary hypertension

Tests that may be done to check for causes of possible secondary hypertension, such as kidney artery problems (renovascular disease) or hormonal (endocrine) problems, include:

• Doppler duplex ultrasound - a test that uses sound waves to detect narrowing of the arteries that supply blood to the kidneys.
• Renal artery angiogram - dye is injected and its course followed through the renal arteries to show any narrowing in the arteries.
• Plasma renin activity determination - a blood test that determines the level of renin, a hormone that plays an important role in blood pressure control.
• VMA and norepinephrine test - the levels of these two hormones are high in certain rare tumours of the adrenal glands that result in hypertension.

Treatment

Home (lifestyle modification)

Most risk factors for essential hypertension are related to poor health habits. About half of all people with mild hypertension can control their condition by adopting healthy habits, which are also preventative.

• Lose weight - the most effective non-drug method of lowering blood pressure. Losing as little as 4,5 kg can lead to a meaningful drop in blood pressure. Weight loss can also enhance the blood pressure lowering effect of anti-hypertensive drugs.
• Exercise - even 30 to 45 minutes of mild to moderate aerobic exercise such as brisk walking or cycling four times a week can nudge your blood pressure down a few points, particularly if you're also losing weight. Vigorous exercise, such as riding a stationary bike for 40 minutes, can lower blood pressure by more than 10 mm Hg. Even people with normal blood pressure who do not exercise and are "out of shape" have a 20 to 50% higher risk of developing hypertension than more active people have.
• Limit alcohol intake - Alcohol raises your blood pressure even if you don't have hypertension and reduces your heart's pumping ability. Heavy drinking not only increases blood pressure, but can also interfere with the effectiveness of blood pressure medications. If you are female, limit your alcohol intake to less than one drink per day; if you are male, limit your intake to two drinks per day. One drink equals 360 ml of beer, 150 ml of wine or 30 ml of distilled liquor.
• Eat a low-fat, high-fruit and -vegetable diet - A recent study found people with hypertension lowered their blood pressure by 11.5 mm Hg systolic and 5.5 mm Hg diastolic through diet alone. 40% of these people were able to stop their medication completely. The diet may have worked because it promoted weight loss and was high in the minerals calcium, potassium and magnesium, which are associated with lower blood pressure.
• Limit salt intake - Not everyone needs to restrict salt intake. However, black people and women older than 65 seem to benefit when they lower their daily sodium intake to no more than 2,4 g per day - about 1 teaspoon of salt. Individual response of blood pressure to salt intake differs widely and is difficult to measure. Most of the salt you eat daily is already added during the preparation of food. Read food labels carefully for sodium amounts.
• Don't smoke - Cigarette smoking doesn't cause hypertension, but is a major risk factor for cardiovascular disease. If you're a smoker, especially one with hypertension, you must stop. And if you're not a smoker, don't start.

For many people, losing weight, exercising regularly, limiting alcohol and sodium and maintaining adequate potassium (3.5 g per day) are enough to lower blood pressure and keep it down.

Medicine

Although lifestyle changes will help, they may not be enough for you. If you can't bring your blood pressure under control by making these changes, you may also need to take medication. Lifestyle changes may still reduce the number and doses of medications needed to control hypertension.

The different classes of drugs used in the treatment of high blood pressure include:

• Diuretics - Also known as water tablets, diuretics (hydrochlorthiazide is most commonly used) are often the first line of drug treatment. Diuretics act on your kidneys to help your body eliminate sodium and water.
• Beta and alpha-beta adrenergic blockers - These drugs (Tenormin, Lopresor, Minipress and others) work by blocking the effects of certain chemicals in your body. With some of these drugs, your heart may beat more slowly and less forcefully. With others, your blood vessels may dilate and you may feel faint when you stand up. These actions on your heart and blood vessels lower your blood pressure.

NOTE: Diuretics and beta-blockers have been proven to reduce the risks associated with hypertension, including heart attacks and strokes. They have been used for many years, their side effects are well-known, and they are generally less expensive than some other blood pressure medications. All antihypertensive classes reduce CVS events with perhaps the exception of alpha blockers.

• ACE inhibitors and angiotensin receptor blockers - Angiotensin converting enzyme (ACE) inhibitors dilate your blood vessels by blocking the formation of the natural body chemical angiotensin II, which constricts blood vessels. However, up to 20% of people who take ACE inhibitors (Capoten, Tritace, Renitec and others) develop a dry, hacking cough. This annoying side effect typically occurs in the 10 to 24 weeks after starting the drug. The cause is unknown. Switching to another type of ACE inhibitor may decrease or stop your cough. The re are also similar anti-hypertensive medications that may not produce a cough. Don't stop taking a medication without first seeing your doctor. These drugs may be particularly effective in patients with diabetes and renal disease.
• Calcium channel blockers - Long acting calcium channel blockers such as AdalatXL and Norvasc help dilate blood vessels and effectively reduce blood pressure for a short or long period. The short-acting drugs aren't recommended for hypertension because control is erratic and some reports have linked them to adverse health effects.

(Reviewed by Dr B. Rayner, nephrologist)

(Health24.com)