Medicine for Africa - Medical Information Service

YPERTENSION

Definition:

Hypertension, or high blood pressure, means a permanent increase of blood pressure in arteries, the vessels that deliver blood from the heart to the organs. 

Hypertension is a precursor of heart attacks (myocardial infarcts) and stroke (cerebrovascular infarcts), especially if long standing and untreated.

Hypertension has been sub-divided into two classes – essential or primary hypertension and secondary hypertension.

Primary hypertension occurs in 90% to 95% of all cases of hypertension without a clearly identifiable cause.  Since it can be caused by genetic factors, a patient’s family history can often predict one’s personal risk of developing hypertension throughout life.  In Africa, the population has an overall risk factor of 50% to 80% of developing hypertension.  Genetically caused differences in the sensitivity to salt (also called sodium or natrium) have been identified.  However, this is just one factor in the area of predisposition; others have not yet been examined sufficiently. 

Hypertension is often accompanied by overweight (in 40% of cases), diabetes, increased lipid and cholesterol levels in blood, as well as increased blood levels of uric acid.  If all these increased blood levels are present in addition to the genetic predisposition, this syndrome is called ‘metabolic syndrome’ or ‘syndrome X’.

Secondary hypertension occurs to about 5% to 10%, and is usually associated with, or secondary to other disease processes, such as hyperthyroidism (increased function of the thyroid gland), disorders in renal (kidney) blood circulation or other kidney abnormalities, certain congenital heart defects, or a benign tumor of the adrenal gland(s).  Also, certain medications, such as birth control pills, some cold remedies and decongestants, certain over-the-counter pain relievers and even some prescription drugs, as well as illegal drugs, such as cocaine and amphetamines, can all result in secondary hypertension.  Furthermore, overweight and smoking are important factors in the development of secondary hypertension, causing at least 60% of all cases.  

Hypertension usually develops in the third or fourth decade of life.  If untreated, the pressure values will slowly rise over years.  Often, hypertension is diagnosed accidentally during a routine exam or because the patient developed symptoms causing him/her to consult a physician.  In less fortunate situations, another disorder or disease leads to the diagnosis of hypertension. 

Diseases of the heart and blood vessels are worldwide number one in mortality.  Most of these cases are caused by untreated or insufficiently treated hypertension.  Myocardial insufficiency (heart failure) and irregular heart beats are a direct result of hypertension, which also fosters the development of arteriosclerosis (‘hardening of the arteries’) in the heart, the brain, the kidneys and the legs.

        Pulmonary hypertension

Pulmonary hypertension is also divided into primary pulmonary hypertension (PPH) and secondary pulmonary artery hypertension (SPAH).

PPH is a rare disease, characterized by an elevated pulmonary artery pressure without any apparent underlying cause.  The diagnosis is usually made after excluding other known causes of pulmonary hypertension.

SPAH is defined as a systolic pressure of the pulmonary artery of higher than 30 mm Hg, or as a pulmonary artery mean pressure of more than 20 mmHg, secondary either to a pulmonary or a cardiac disorder.  Cardiac and/or pulmonary disorders are the most common causes of secondary pulmonary hypertension.

Symptoms:

The disease ‘hypertension’ often starts without causing any noticeable symptoms.  Occasionally, patients may complain about migraines or tension headaches for many years prior to the diagnosis of hypertension.  Especially women reported at times that they received treatment for low blood pressure when they were young.

At the time that hypertension is diagnosed, it is often accompanied by an increase in pulse pressure, above the normal rate of 60 to 80 beats per minute.  Increased pressure values can cause headaches, vertigo, heart palpitations, shortness of breath, numbness (especially in fingers and feet), and water retention (edema), particularly in the lower legs.

 
Diagnosis:

Hypertension is diagnosed by taking the patient’s blood pressure under standardized conditions at rest from the upper arm with a blood pressure meter, called sphygmomanometer, and measuring the upper value – the systolic pressure, and the lower value – the diastolic pressure.  The limits of the systolic and diastolic pressure values for the diagnosis of hypertension often vary slightly, depending on the medical research used for diagnosis.  However, in general, systolic pressure values greater than 140 mm Hg (hydrargyrum = mercury) and diastolic pressure values greater than 90 mm Hg are considered consistent with hypertension.  A diagnosis of hypertension is made if at least one value (systolic or diastolic) is increased at three independent times of testing.

Following the diagnosis of hypertension, regular urinalysis should be performed, in order to assess the kidney functions and to examine the urine for the presence of infections, proteins and glucose.

In addition, blood levels of thyroid hormone and glucose should be determined; in order to rule out or diagnose hyperthyroidism or diabetes, respectively.  Further examinations may include blood level determinations of renin, a sonography of the kidneys, color flow Doppler scanning of the renal vessels (to determine the presence and extent of arteriosclerotic changes of the renal vessels), as well as the determination of vanillyl mandelic acid (VMA, a metabolite of the catecholamine norepinephrine) in the urine.  

 
Treatment:

Primary hypertension can often be successfully treated by permanent weight reduction.  In case of overweight, permanent weight reduction would also improve the effect of drug treatment.  In some cases, drug treatment can completely be abolished after achieving a normal weight level.  However, since most overweight people are not able to sufficiently reduce their weight, the majority of these patients will have to take drugs permanently.  This can also be the case for people with normal weight.  Both groups have to understand that only continuous treatment will be able to normalize the risks for heart, vessels and organs.

In addition, regular exercise – aerobic and isotonic exercises – have a direct beneficial effect on the blood pressure, while concomitantly helping in achieving weight reduction or maintaining appropriate body weight.

There are a large number of drugs available for treatment, which can be given as a single dose or in combination.  The appropriate selection depends on the symptoms caused by the hypertension (values, pulse pressure, edema), on the presence of other diseases (diabetes, myocardial insufficiency [weakness of the heart muscle], irregular heart beat, coronary disorders, asthma, adenoma of the prostate), as well as on the age and sex of the patient.

Pressure lowering classes of drugs include:

• Diuretics – are substances that cause the loss of water (e.g. lasix),
• Calcium antagonists or calcium channel blockers – dilate the blood vessels (e.g. benzodiazepine or dihydropyridine),
• ACE-inhibitors (ACE – angiotension-converting-enzyme) – are effective against pressure increasing renal substances and improve myocardial insufficiency (e.g. lisinopril or enalapril),
• Angiotension-II inhibitors – function similar to ACE inhibitors,
• Alpha blockers – dilate blood vessels, and are also suitable for adenoma of the prostate; they are also called adrenergic alpha antagonists (e.g. phenoxybenzamine, phentolamine),
• Beta blockers – primarily used for the treatment of cardiac arrhythmias, for cardioprotection after myocardial infarct (heart attack), but also for hypertension (e.g. propranolol).

In general, the therapeutic effect on lowering blood pressure can be increased by combining drugs from different classes.

All forms of secondary hypertension should be treated according to the underlying disease. 

Hyperthyroidism treatment includes drugs or surgery. 

Hypertension caused by renal factors is more difficult to treat.   Therapy depends on the specific origin of the problem.  In some cases, it may be necessary to remove one kidney.

 
Prevention:

There are no effective measures against secondary hypertension.

Essential or primary hypertension, the cause of most cases, can be held in check by a variety of measurements.  Maintaining normal body weight, or achieving it, is clearly the most important of them all.  Secondly, abstaining from too much sugar consumption and reducing the amount of carbohydrates in food, are other important preventive measurements, since both substances will be metabolized to glucose in the blood and cause the release of insulin from the pancreas.  The faster and higher the glucose concentration in blood increases, the more insulin will be produced; a chronic increase in insulin production fosters the development of diabetes and probably also participates in the development of high blood pressure.

In 20% of patients with hypertension, a decreased consumption of salt can already improve their blood pressure – these patients are said to be sodium sensitive.

Regular light exercise and a well balanced diet with a controlled body weight are among the most important preventive measurements.  In addition, a balanced life style without stress and unhealthy habits such as smoking and consuming too much alcohol cannot only prevent hypertension, but also a whole range of other diseases and disorders. 

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