Hypertension is an abnormal elevation of blood pressure. It is an important and potentially treatable cause of cardiovascular disease and death. Up to 15% of the adult population have high blood pressure with increasing age.
Attempts to define normal blood pressure are difficult as it may vary throughout the day and due to the effects of age, sex and race.
In about 10% of cases hypertension is secondary to renal or endocrine disorders but in the remainder the aetiology is unknown (essential hypertension). Evidence does point to a complex interaction of hereditary and environmental factors.
Rare causes include narrowing of the artery supplying the kidney and endocrine abnormalities such as Cushing?s syndrome, acromegaly, and thyroid disease. The blood pressure is determined by the output from the heart and the tension in the vascular system. It is nearly always the elevation of the tone in the vascular system which plays a major role.
These changes may be precipitated by the local secretion of an enzyme in the arteriolar wall or due to abnormalities in the kidney of sodium excretion leading to salt and water retention.
Symptoms and Signs
Many patients do not complain of any symptoms and the raised blood pressure is discovered during unrelated examination or during screening programmes. Diagnosis may only be found when a complication occurs such as a heart attack or stroke. Headaches occasionally occur but shortness of breath and angina is rare.
The clinical signs depend on the elevation of the blood pressure. In mild hypertension the only signs are raised blood pressure on measurement. In moderate to severe high blood pressure secondary changes may be seen in the vessels on the retina of the eyes and early signs of heart damage. When the blood pressure is very high signs of heart failure
, kidney failure and strokes may be present.
Complications of the Disorder
Major complications of high blood pressure are heart disease, stroke, damage to the retina of the eye, kidney failure and vascular changes resulting in decreased blood supply to the limbs.
Investigation includes blood pressure measurement, chest X-rays, urine analysis, changes in the electrocardiogram or echocardiography may be seen in moderate to severe high blood pressure.
Treatment should be aimed not only at medical treatment but also on diet and lifestyle.
The patient should be advised to stop smoking, reduce weight and reduce excessive alcohol consumption. If salt intake in the diet is excessive this should be reduced. Exercise should be encouraged e.g. 1 hours walk 3 times a week. Medication which contributes to high blood pressure such as the contraceptive pill should be stopped.
Medical treatment is only commenced when the blood pressure remains high, as in 25% of cases the blood pressure will settle within 3 months.
There are 5 classes of drugs that are normally used to treat hypertension:
A selective beta-blocker is normally chosen in a once a day dosage, this minimizes the side-effects but care should be taken if there is respiratory illness. These should not be prescribed in the presence of asthma, heart failure or heart block.
In diuretics the reduction in blood pressure may take several weeks after commencing the diuretics. Low doses have been found to be just as effective as high doses and are particularly beneficial to the elderly patient.
Written by Medpages Editorial Team
Last Editorial Review: 25/1/2010