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ECG – heart tracing to look for signs of left-ventricular thickening, irregular heartbeat or evidence that the heart muscle is struggling
analysis of a urine sample – to look for protein and sugar, which would suggest blood vessels in the kidney are damaged
blood test for urea and electrolytes – to check kidney function and your salt balance
blood test for fasting blood lipids – to see if your blood cholesterol or other fat levels are raised.
If your doctor suspects your blood pressure is due to an underlying cause, you may have one or more of the following tests carried out:
If your potassium level is low, and you are not on diuretic treatment, you may have a hormone problem leading to high blood pressure. You will therefore have blood tests taken to check levels of other hormones such as aldosterone, cortisol and renin.
Blood tests to assess kidney function (creatinine clearance rate).
An intravenous urogram – a substance that shows up on x-ray is injected into your blood stream and a series of x-rays taken. This shows any narrowing of your renal arteries, how well your kidneys concentrate the dye in the urine, and outlines your urinary system to show up anatomical abnormalities or shrinkage of the kidneys.
Ultrasound of your kidneys.
Blood tests to measure catecholamine levels or measurement of urinary vanillylmandelic acid if phaeochromocytoma (tumour of the adrenal gland) is suspected.
If acromegaly is suspected from changes to your facial features and the fact that your tongue, jaw, hands and feet are getting bigger, you will have your blood levels of growth hormone measured.
EYE EXAMINATIONS
High blood pressure damages small arteries throughout your body. Those in the back of the eye have the advantage of being visible using an ophthalmoscope and they show the state of arterioles throughout your system, including your brain. Early changes due to hypertension include thickening of retinal blood vessel walls. If hypertension becomes long-standing or severe, the blood vessels leak and little haemorrhages form. Other changes are probably due to obstruction of vessels and reduced blood circulation.
Your doctor will regularly check the back of your eyes for signs of damage if your blood pressure has been high. This is performed in a darkened room using an ophthalmoscope, which contains a number of lenses and a light source. Sometimes you may have one eye dilated first with drops to make the task easier. The doctor is looking for various abnormalities known as Keith-Wagener retinal changes. These are divided into four stages of severity:
Grade 1 – retinal arteries are more tortuous i.e. less straight. Because they are thickened and bulging under pressure, they also reflect light from the ophthalmoscope more than usual. This gives them an appearance known as silver wiring.
Grade 2 – as in grade 1, plus evidence that the thickened, bulging arteries are compressing the veins where they cross over them (arterio-venous nipping).
Grade 3 – as in grade 2, plus signs that the arteries have started leaking. Leakage of protein-rich fluid produces white, soft, ‘cotton wool’ – like blobs while leakage of blood produces flame-shaped haemorrhages.
Grade 4 – as in grade 3, plus swelling, bulging and blurring of the head of the optic nerve (papilloedema).
If haemorrhages, exudates or papilloedema are visible in the back of the eye, it shows that malignant hypertension (see page 5) has developed. These are the same sort of processes that are occurring in the brain and which are thought to lead to a stroke. It is very important that your hypertension is brought under control quickly and safely. You may be admitted to hospital for complete bed rest while your drug treatment is adjusted.
Peripheral Vascular Disease
Hardening and furring up of the arteries throughout the body can lead to peripheral vascular disease in which blood supply to your legs is severely limited. Even a mild increase in exercise means that your muscles need extra blood and oxygen – if these cannot be supplied, your leg muscles will start to cramp. This causes a severe pain in the calf muscles which comes on during exercise and stops when you rest – a condition called intermittent claudication. If your blood supply is severely affected, even walking 100 metres or less on the flat can bring symptoms on. If blood supply is very poor, ischaemic pain may occur at rest, tissues may break down to form a leg ulcer and eventually gangrene may set in. Severe peripheral vascular disease is most likely in someone with hypertension who also smokes, or who also suffers from diabetes.
Aspirin will help to thin the blood and improve blood supply. Some tablets also work by increasing the flexibility of red blood cells so they can squeeze through small blood vessels more easily. Interestingly, research shows that taking garlic powder tablets, ginkgo biloba or a mix of Tibetan herbs known as Padma 28 can improve peripheral circulation enough to increase the distance you can walk before calf pain starts by up to 30 per cent in three months (see Chapter 19).
A severely narrowed artery in the leg can be overcome with a bypass graft to open up an alternative circulatory route. If there are only one or two main sites of blockage, these can sometimes be overcome by passing a balloon catheter into the artery and expanding it at the site of blockage to locally dilate the vessel in that area.
Treatment of High Blood Pressure
Early diagnosis and treatment can control your blood pressure before it harms your health. You will have your blood pressure measured several times before your doctor will decide to prescribe any anti-hypertensive drugs. This is to make sure your blood pressure remains consistently high and is not just going up as a result of visiting the surgery. The aim of blood-pressure treatment is to reduce diastolic BP to below 85 mmHg and/or systolic BP to below 140 mmHg (thresholds may be different in some groups of people such as the very elderly). Sometimes two or even three different types of drug are needed to achieve this goal.
The aim of treatment is to lower your blood pressure gradually. Your doctor will start you off on a low dose of tablets to see how your blood pressure responds. If this is not enough, your dose may be increased, other drugs may be added in, or your medication may be completely changed. In some cases, more than one drug may be needed to achieve an acceptable BP. It may seem annoying to have to take one, two or even three different kinds of drugs when you feel perfectly well. But by prescribing treatment to keep your blood pressure within normal limits, your doctor is helping you to avoid the complications of uncontrolled hypertension – heart attack, stroke, peripheral vascular disease, kidney failure and even blindness.
It is important to take your blood pressure tablets regularly as prescribed. Some tablets only need only to be taken once a day, but others may need to be taken two or more times daily. This depends on how long each dose of medicine works in your body, and on how bad your blood pressure is.
When most forms of anti-hypertensive treatment are stopped, blood pressure only climbs up only slowly over several days or even weeks. With some forms of treatment, however, a rebound effect can occur so your blood pressure shoots back up.
Don’t stop taking your blood pressure treatment without first consulting your doctor. If you notice something that may be a side-effect, such as a rash, dizziness or sexual problems, always tell your doctor immediately so your dose can be altered or your treatment changed to one that suits you better.
Research shows that controlling hypertension can:
lower the risk of stroke by 35 per cent
reduce the risk of heart complications by 20 per cent
reduce overall risk of death at any age by 15 per cent.
GUIDELINES FOR DOCTORS
Doctors have been given guidelines to help them decide which patients with high blood pressure need treatment and which don’t. Basically, if your BP is consistently found to be above a certain level, it is important to bring it down to normal to reduce your risk of future complications such as coronary heart disease, kidney failure, eye problems (hypertensive retinopathy) or stroke. If complications (target organ damage) are already in evidence, the management of your condition will be stepped up.
These guidelines are based on extensive studies and trials that confirm the health benefits of treatment. In some cases, where blood pressure is borderline, and research does not show clear benefits of treatment, your doctor will monitor you regularly to make sure your BP does not go up. In these cases, diet and lifestyle changes are often enough to control your BP so you don’t need to take drug treatment at all.
You might find it interesting to read the guidelines given to doctors. These are as follows:
Measurement
Baseline BP is established by taking two to three BP readings per visit (while the patient is sitting) on up to four occasions.
Aims of Treatment
To reduce diastolic BP to less than 85 mmHg and to reduce systolic BP to less than 140 mmHg, but the optimal target in people with diabetes or kidney disease is lower. In the elderly, the threshold for treatment is usually higher, as research only shows consistent benefits in treating a BP that is persistently raised to 160/90 or greater.
Target Organ Damage
This is defined as left ventricle of heart enlarged; angina; transient ischaemia attacks (TIAs); stroke; peripheral vascular disease; heart attack; kidney function impaired.
Where the initial blood pressure is systolic ≥ 220mmHg OR diastolic ≥ 120mmHg, treat immediately.
Where the initial blood pressure is systolic 200–219 mmHg OR diastolic 110–119 mmHg, confirm over one to two weeks then treat if these values are sustained.
Where the initial blood pressure is systolic 160–199 mmHg OR diastolic 100–109 mmHg, AND the patient has cardiovascular complications, end organ damage or diabetes (type I or II), confirm over three to four weeks then treat if these values are sustained.
Where the initial blood pressure is systolic 160–199 mmHg OR diastolic 100–109 mmHg, but the patient has NO cardiovascular complications, end organ damage or diabetes, advise lifestyle changes, reassess weekly initially and treat if these values are sustained on repeat measurements over four to twelve weeks.
Where the initial blood pressure is systolic 140–159 mmHg OR diastolic 90–99 mmHg, AND the patient has cardiovascular complications, end organ damage or diabetes, confirm within four to twelve weeks and treat if these values are sustained.
Where the initial blood pressure is systolic 140–159 mmHg OR diastolic 90–99 mmHg, but the patient has NO cardiovascular complications, end organ damage or diabetes, advise lifestyle changes, reassess monthly; if mild hypertension persists, treat if the risk of coronary heart disease is greater than or equal to 15 per cent over the next 10 years using the Joint British Societies Coronary Risk Prediction Charts (which give a predicted future CHD risk depending on age, gender, smoking status, systolic blood pressure, cholesterol levels and diabetic status).
DRUGS USED TO TREAT HYPERTENSION
At present, six classes of drug are available to lower high blood pressure:
thiazide diuretics
beta-blockers
alpha-blockers
calcium channel blockers
ACE inhibitors
angiotensin-II receptor antagonists.
If a single drug is not effective, other anti-hypertensive drugs may be added, usually at intervals of at least four weeks, until good control of BP is achieved. Where hypertension is relatively mild (systolic BP less than 160mmHg, and diastolic less than 100mmHg), drugs may be substituted rather than used together.
Thiazide Diuretics
Thiazide diuretics (e.g. bendrofluazide, hydrochlorothiazide) are generally used as a first-line treatment in the elderly, or are combined with other anti-hypertensive drugs (e.g. a beta-blocker or ACE inhibitor) to boost their action in younger patients.
They lower blood pressure by increasing loss of salts through the kidneys into the urine. This tends to draw fluid out of the circulation, causes mild dilation of small arteries and lowers arteriolar resistance. The diuretics act within an hour or two of being given and are usually taken in the morning so you do not have to get up at night to pass water. When you first start taking the tablets, you may notice that you have to pass water more frequently than usual for the first few days;, then this effect tends to disappear as dilation of the arterioles occurs. Only low doses of hiazide diuretic are needed to bring your diastolic BP down by around 5 mmHg – higher doses have no further effect on BP and are more likely to cause side effects such as salt imbalances.
They should not be used by people with diabetes or with sodium, potassium or calcium imbalances, severe kidney or liver problems, active gout or Addison’s disease.
Beta-blockers
The way beta-blockers lower blood pressure is not fully understood but is thought to result from a combination of actions in which they:
alter the way nerve signals cause some blood vessels to dilate or constrict
slow the heart rate to around 60 beats per minute
reduce the force of contraction of the heart
decrease the workload of the heart and cardiac output
lower secretion of a kidney hormone, renin
reduce sensitivity of blood pressure sensors (baroreceptors)
block stress hormone (adrenaline) receptors
have some effects on the brain.
In general, beta-blockers are used as a first-line treatment in young people with hypertension and in people who have coronary heart disease. Because they also affect receptors in the lungs, they should not be used in people with asthma as they may trigger an asthma attack. Beta-blockers have been shown to significantly reduce the risk of having a second heart attack and may prolong life in high-risk individuals.
Beta-blockers should not be withdrawn suddenly, but must be tailed off slowly so that rebound high blood pressure (or angina) does not occur.
Alpha-blockers
Alpha-blockers (e.g. doxazosin, indoramin, prazosin, terazosin) lower blood pressure by dilating both arteries and veins. They are particularly helpful for older males who have both high blood pressure and problems associated with benign enlargement of the prostate gland. They sometimes cause a rapid fall in blood pressure after the first dose so treatment should be started with caution – usually at night so that if low blood pressure does occur, this is after you have retired to bed.
If taking Indoramin, you should avoid alcohol as it boosts alcohol absorption.
Calcium Channel Blockers
Calcium channel blockers (e.g. diltiazem, felodipine, isradipine, lacidipine, nicardipine, nifedipine) work by:
blocking the transport of calcium ions through cell membranes
relaxing muscles in arterial walls and reducing arterial spasm
dilating peripheral veins to encourage pooling of blood
dilating peripheral veins to encourage pooling of blood
reducing the force of contraction of the heart.
Treatment must not be stopped suddenly, but should be tailed off slowly to prevent rebound angina. Verapamil is slightly different from the others in the way it works, and should not be used together with a beta-blocker.
ACE Inhibitors
ACE inhibitor drugs are so-named because they block formation of Angiotensin Converting Enzyme (ACE). This in turn prevents formation of a substance called angiotensin II – a powerful constrictor of blood vessels – leading to dilation of both small arteries and veins. This reduces total peripheral resistance and arterial blood pressure. ACE inhibitors also increase blood flow to the kidneys, so more fluid and sodium is lost as urine. They are usually considered for treating hypertension when thiazides diuretics or beta-blockers are contraindicated, not tolerated, or fail to control high blood pressure.
They can cause a sudden fall in BP on giving the first dose, especially in people who are taking diuretics or who are dehydrated. Where possible, diuretic treatment is therefore usually stopped a few days before ACE inhibitor treatment is started. For some, the first dose is best taken at night on retiring to bed. Kidney function and salt balance should be checked before treatment is started. ACE inhibitors may be less effective in people of Afro-Caribbean descent unless combined with a thiazide diuretic.
Angiotensin-II Receptor Antagonists
These drugs (e.g. losartan, valsartan, candesartan) are similar to the ACE inhibitors except that instead of inhibiting angiotensin-converting enzyme, they block angiotensin-II to produce similar effects. This dilates blood vessels, stimulates kidney function and may also have a direct action on the brain to reduce drinking and increase urine output. At present, they are mainly used in people who develop a persistent dry cough as a troublesome side-effect of the ACE inhibitors as these particular drugs do not produce this problem.
Other Drugs
Occasionally, drugs from the above groups may not be sufficient or suitable for treating an individual case of high blood pressure. Two other drugs are sometimes used: hydralazine or methyldopa.
Hydralazine is a vasodilator that lowers blood pressure by relaxing arteries and increasing their diameter. When used to treat hypertension, it is usually combined with a beta-blocker and thiazide diuretic to stop the heart rate and cardiac output from increasing and to avoid fluid retention. It may cause a very rapid drop in blood pressure.
Methyldopa used to be the most popular drug for treating high blood pressure, and may still be taken by elderly patients who started on it many years ago. It lowers blood pressure by acting on the brain to trigger nerve actions that reduce heart output, urine production and arteriolar constriction. Methyldopa is often used together with a diuretic. It may cause a rapid fall in blood pressure, especially in the elderly.
Your doctor may also suggest taking low-dose aspirin or taking drugs to lower blood cholesterol levels if necessary.
IS ANTI-HYPERTENSIVE TREATMENT FOR LIFE?
Once drug treatment is started for high blood pressure, it is often for life. However, if you don’t have any complications from your high blood pressure and you have managed to make diet and lifestyle changes that naturally bring your blood pressure down, it may be possible to reduce your tablet dose or to withdraw it altogether. However, you should never alter your medication or stop it suddenly yourself. If your doctor decides to withdraw your treatment, this is usually done slowly in a step-wise fashion to prevent a sudden rebound hypertension. You will be followed up closely over a long period of time, as, in some cases, BP starts to creep back up again after six months, a year or more.
IF YOU SHOULD FORGET TO TAKE YOUR MEDICATION
If you do forget to take your treatment occasionally, it is unlikely that you will come to any harm. If you forget your tablets on a regular basis, however, you may run into problems.
If your treatment is only a few hours late, take it as soon as you remember.
