What is it?
Hypertension is persistently high pressure in the arteries that can, over time, cause damage to organs such as the kidneys, brain, eyes, and heart.
Arterial blood pressure, the amount of force blood exerts on the walls of the arteries, depends on the force and rate that the heart contracts as it pumps oxygenated blood from the left ventricle (compartment) of the heart into the arteries and the resistance to that flow. The amount…
Signs and Symptoms
Occasionally high blood pressure causes headaches, but in most cases there are no symptoms until it begins to damage body organs. For this reason hypertension is sometimes referred to as the “silent killer,” quietly increasing the risk of developing stroke, heart disease, heart attack, kidney damage, and blindness. Very high blood pressure may cause breathlessness, blurred or double vision and nose bleeds as well as a persistent headache.
Because hypertension is both a quiet and a common condition, blood pressure is often measured each time a patient sees their doctor. Nearly a third of UK residents with high blood pressure do not know about it and are not being treated.
The goals of testing are to detect high blood pressure, to confirm that it is persistent over time, to find out whether it is being caused by an a treatable disease, to check the health of various body organs, to get baseline values prior to starting treatment, and to monitor blood pressure and organ health during treatment.
Laboratory Tests
Laboratory tests cannot diagnose hypertension, but are frequently requested to help evaluate and monitor organ function. Specific tests are sometimes requested to detect diseases that may be causing the high blood pressure or making it worse.
General tests that may be requested include:
Urinalysis including Urine Albumin to Creatinine Ration (ACR) – to help assess kidney function
Urea and Creatinine – to detect and monitor kidney disease or to monitor the effect of drug treatment on the kidneys
Electrolytes sodium and potassium – some high blood pressure treatments can cause high sodium and potassium loss
Fasting Glucose – to detect diabetes
Calcium – increased activity of the parathyroid glands produces an increase in serum calcium which can be associated with high blood pressure
Lipid Profile – to check levels of total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides because persistent hypertension promotes hardening of the arteries (atherosclerosis)
Specific tests that may be requested because of the patient’s medical history, physical findings or general laboratory test results to help detect, diagnose, and monitor conditions causing secondary hypertension include:
Aldosterone and Renin – to help detect the overproduction of aldosterone by the adrenal glands (which may be due to a tumour)
Cortisol – to detect an overproduction of cortisol that may be due to Cushing’s syndrome
Catecholamines and methylated amines – adrenaline, noradrenaline and their metabolites and are used to help detect the presence of a phaeochromocytoma (a tumour of the adrenal gland) that can cause episodes of severe hypertension
Parathyroid hormone (PTH) – if calcium is found to be increased
TSH (Thyroid Stimulating Hormone) and free T4 – to detect and monitor thyroid dysfunction
Non-Laboratory Tests
Blood pressure measurement
This is the primary tool for detecting and monitoring hypertension. There is a good description of how blood pressure is measured in the British Heart Foundation blood pressure booklet.
Blood pressure measurements are usually performed after the patient has been sitting quietly for at least five minutes but may also be done in other postures, such as standing. If a patient has an elevated blood pressure, the pressure in the other arm may be measured to confirm the finding.
Since blood pressure can and will vary, a diagnosis of hypertension is not made from a single measurement, but involves multiple measurements made at different times. It is not a single high reading that the doctor is interested in, but persistent high blood pressure.
The doctor may ask the patient to wear a device that monitors and records the blood pressure at regular intervals during the day to monitor it over time. This is especially helpful during the diagnostic process and can help rule out the high measurements that only occur when the patient is in the doctor’s surgery. This is known as the “white coat phenomenon,” which has been estimated to account for as much as 10-20% of suspected cases of hypertension. There are electronic blood pressure measuring devices that can be used in the home. These can be used effectively but should be checked at intervals against the findings at the doctor’s surgery to ensure accuracy.
These forms of blood pressure measurement are considered indirect. Very rarely, a direct measurement of blood pressure may be required. This can be obtained by inserting a catheter into an artery to measure the pressure inside the blood vessel.
As part of the diagnostic process and to help evaluate the status of vital organs, the doctor would normally carry out:
Eye examination – to look at the retina for changes in the appearance of the blood vessels (retinopathy)
Physical examination – to help evaluate the kidneys, to look for abdominal tenderness, to listen for bruits (the sound of blood flowing through a narrowed artery), to examine the thyroid gland in the throat for enlargement and to detect any other clinical signs present
Other possible tests are: ECG (electrocardiogram) to evaluate the heart rate and function, and imaging scans, such as an X-ray or ultrasound of the kidneys or X-ray of the chest.
Treatment
Lifestyle changes can help lower blood pressure and are advised for all patients. In those with mild hypertension (a systolic preassure of 120-139 and/or a diastolic of 80-89mm Hg), reaching and maintaining a healthy weight, exercising regularly, limiting dietary alcohol and salt, and stopping smoking can reduce blood pressure levels to normal and may be the only “treatment” required. The risks associated with gender, race and increasing age, however, do not disappear with lifestyle changes and, in most other patients, a treatment plan that includes medicines is necessary to control persistently high blood pressure.
There are several classes of drugs available to treat hypertension. Each class works differently, targeting a particular aspect of blood pressure regulation. Frequently, a patient will need to take a couple of different drugs together to achieve blood pressure control. Your doctor will work with you to select the combinations and dose that are right for you. Classes that are available include:
Diuretics – a commonly used group of drugs that increase the removal of salt and water by the kidneys. This reduces the volume of fluid in circulation and lowers the blood pressure.
Adrenergic blockers (alpha blockers, beta blockers, alpha-beta blockers) – work to reduce the nervous system’s rapid response to physical and emotional stress.
ACE (angiotensin-converting enzyme) inhibitors and ARBs (Antiotensin II receptor blockers) – help prevent the constriction of arterioles (small arteries) by blocking the formation and/or action of angiotensin II, an enzyme that the body produces to constrict blood vessels and increase blood pressure.
Calcium channel blockers – dilate arterioles by decreasing the amount of calcium that enters into the blood vessel walls and the heart muscle.
Vasodilators – work directly on blood vessels to relax the muscles that constrict and dilate the arteries.
If a condition causing secondary hypertension can be cured (for example, by removing an adrenal tumour) or controlled (for example, by treating diabetes or thyroid disease), then blood pressure levels may fall to normal or near normal. When a cure is not possible and control of the disease consists of minimising further damage (as may occur with kidney disease), then the hypertension will be controlled with a combination of medicines, and the patient will be monitored closely to help maintain organ function and reduce the likelihood of problems arising.
Any patient, asymptomatic or not, who has severe hypertension with a blood pressure over 180/110 mm Hg or who has hypertensive changes in the retina on eye examination must be treated urgently and may require admission to hospital.
In about 4% of first pregnancies mothers develop a combination of increased blood pressure and protein in the urine called pre-eclampsia. In the last three months of pregnancy about one in 50 develop full eclampsia with fits, fluid in the lungs, kidney failure and clotting problems.
Women with pre-eclampsia require rest, close monitoring, and frequent visits to their doctor’s surgery or even admission to hospital. The only real solution for pre-eclampsia is delivery, but postponing delivery as long as possible allows the foetus more time to mature. This time delay must be balanced against the increasing danger of the development of full eclampsia that can be life-threatening for both baby and mother.