Hypertension or High Blood Pressure
Hypertension is persistently raised blood pressure (the pressure of blood in the main arteries). Blood pressure goes up temporarily as a normal response to stress and physical activity, and it rises naturally with increasing age and weight. A person with hypertension, however, has persistently high blood pressure even when at rest. Because the condition itself causes no symptoms, a large number of people have hypertension without realizing it; however, because hypertension causes the risk of developing serious cardio-vascular disorders to increase, regular medical checks are advised in order to detect the condition at an early stage. Hypertension is very common, particu-larly in men, and its incidence is highest in the middle-aged and elderly. Blood pressure is measured as two values, each expressed as millimetres (mm) of mercury (chemical symbol Hg) or mmHg. The systolic value (the higher value) is the pressure when blood surges into the aorta from the heart; the diastolic value is the pressure when the ventricles (lower chambers of the heart) relax between beats. A blood pressure consistently exceeding about 140 mmHg (systolic) and 90 mmHg (diastolic) at rest is defined as hypertension.
SYMPTOMS AND COMPLICATIONS
Hypertension is usually symptomless, and generally goes undiscovered until detected during a routine physical examination. However, if it is severe or accelerated (known as malignant hypertension) it may cause headaches, breathlessness, and visual disturbances. The condition puts considerable strain on the heart and blood vessels, increasing the risk of stroke, coronary artery disease, and heart failure. Hypertension may eventually lead to kidney damage and retinopathy (damage to the retina at the back of the eye).
In many cases, there is no obvious cause, in which case the condition is called essential hypertension. Genetic factors are important, although hypertension is not attributed to a specific gene. Other factors that are associated with hypertension include high alcohol intake, a high-salt diet, obesity, diabetes mellitus, a sedentary lifestyle, and smoking. There is also evidence that low birth weight increases the risk of developing hypertension in later life. If hypertension results from a specific disorder, the condition is known as secondary hypertension. Causes include various kidney disorders; certain disorders of the adrenal glands; pre-eclampsia (a complication of pregnancy); coarctation of the aorta (a congenital heart defect); and the use of certain drugs. Taking the combined contraceptive pill can lead to hypertension in susceptible women.
The patient’s blood pressure is measured at rest on several occasions in order to make a diagnosis. If there is any doubt, an ambulatory blood pressure device is fitted to monitor blood pressure over a 24 hour period. This may detect a condition known as white coat hypertension, in which blood pressure is raised during a test by a doctor, but it is otherwise normal and does not require treatment. The eyes may also be examined for evidence of long-standing hypertension. If secondary hypertension is suspected,blood tests, X-rays, and other appropriate tests are carried out to exclude any potential causes.
With mild to moderate hypertension, if no underlying cause is found, lifestyle changes are recommended as the first line of treatment. For example, smokers should give up their habit and drinkers should reduce their consumption of alcohol. Any overweight person with hypertension should try to lose weight by modifying the diet and introducing gradually increasing amounts of exercise into the daily routine. Biofeedback training and relaxation techniques can also help to reduce blood pressure. If self-help measures have no effect, or if hypertension is severe, anti-hypertensive drugs may be given. There is a large range of drug treatments available and the treatment chosen depends on the presence of other disorders, such as diabetes mellitus. The response of the condition to treatment, as well as any side effects it has provoked, may prompt a change of treatment. Usually, the patient is monitored by having regular blood pressure checks, so that adjustments to drug type or dosage can be made if necessary. It may be possible for the patient to monitor his or her own blood pressure at home, but the individual’s machine should be checked regularly and calibrated against the doc-tor’s machine. In many cases, drug treatment must continue for life, but this may help to extend life expectancy significantly.