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(6) High Blood Pressure

 Diagnosis

How do doctors diagnose high BP?

Measuring your BP is by far the most important routine test before a diagnosis can be made. It is very important that you have repeated measurements of your BP over time, so as to make sure that your average reading is estimated accurately. At a minimum, three readings should be taken on four or more separate occasions. For all but very severe cases of high BP, decisions about treatment are much better after 2 weeks or so of twice daily home readings.

I am going for my repeat BP test next week as my first one was high. What questions will I be asked?

Any doctor or nurse who is meeting you to find out why you have high BP will ask questions, examine you and order investigations in a structured manner. The following list is an outline of what you might expect to be asked:

• Was the BP measurement different from or the same as your normal BP?

• Did this measurement worry you?

• Did you hurry to your appointment?

• Was it very cold outside?

• Had you a full bladder?

• Was there any other reason why any kind of discomfort or anxiety might have pushed up your BP?

Doctors or nurses measuring BP are all taught to look for reasons of this sort for unexpectedly high values, but many are too rushed themselves to do so. A rapid pulse often gives a clue to anxiety or vigorous exercise within the previous 10-15 minutes.

You will then be asked questions about yourself, your past medical and family history and other associated risks that you might have that are associated with high BP. In more detail the following points should be covered:

• A note of your current age and sex.

• A review of some important symptoms that you might have.

These are important when assessing whether you have ever suffered any complications from having high BP. Questions will include any recent symptoms of: chest pain; shortness of breath; dizziness episodes; blurred vision; slurred speech; memory loss; leg pain.

• Your past medical history, which might include heart attack (‘myocardial infarct’); angina; stroke; transient ischaemic attack (TIA-a mini-stroke where symptoms of weakness resolve entirely within 24 hours); memory loss; left ventricular hypertrophy (thickening of the heart vessel wall); heart failure; heart operations including coronary angioplasty or bypass surgery; diabetes, kidney disease (a broad term for a variety of different conditions that result in reduced kidney function; in some situations, where kidney function reduces progressively over time, ‘end-stage’ kidney failure occurs where the kidney’s excretory function breaks down and you would require dialysis), and coarctation of the aorta (narrowing of the main blood vessel leading from the heart).

• Whether anybody in your family had an early stroke or a heart attack or diabetes.

• Your family history of high BP. People without any family history of high BP are more likely to have a rare, surgically treatable cause of high BP, such as a kidney disorder or coarctation of the aorta.

• Whether you smoke, drink excessively and what your diet is like.

• What drugs you are taking, specifically those that are associated with having high BP: corticosteroids; no steroidal anti-inflammatory drugs (NSAIDs); amphetamines (appetite suppressants); caffeine intake, sympathomimetics (found in nasal decongestants or bronchodilators); oral contraceptives; sodium-containing medications (antacids).

You will then be examined and the following tests should be done:

• Your BP levels will be measured – the way in which this is done and how often it is done is critical to whether you are classified as having high BP or not.

• Your height and weight will be measured, which will allow the doctor or nurse to calculate your body mass index.

• You should be examined for absent or suspiciously reduced pulses over the femoral arteries, felt in your groin creases.

This is the classical sign of coarctation of the aorta, rare but easily detected, for which there is very effective surgical treatment.

• “End organ’ damage (damage caused to the eyes, heart, circulation and kidney owing to prolonged high blood pressure) will be assessed. This includes an eye examination, looking for fundal haemorrhages or exudates; an examination of your heart, looking for evidence of heart failure or left ventricular hypertrophy.

• Your abdomen will be examined so that any swelling of your aorta (main artery in your body) can be excluded.

Remember that ‘classical’ causes of secondary high BP are all rare, accounting for less than 1% of all cases of treated high BP. In practice they are usually searched for in two stages: before treatment begins and if treatment unaccountably fails.

Will the doctor do some tests straightaway?

All people should have the following tests done as early as possible:

• Urine test: to check for protein and sugar in the urine.

Leakage of protein may indicate that the kidneys have been damaged from high BP and you will need more detailed assessment of your kidney function. Testing for sugar is a relatively straightforward way of checking for diabetes. Similarly, if sugar is present, then blood tests will be needed to confirm or rule out diabetes.

• Blood tests: to measure urea, electrolytes and creatinine levels; total cholesterol/HDL cholesterol.

• X-rays and ECGs: Routine chest X-rays and X-rays of the kidney (‘pyelography’) are not necessary or useful for routine initial assessment. Electrocardiograms (ECGs) give much less information about heart function than most people think. They require careful evaluation, and interpretation is full of pitfalls. However, interpretation of any future chest pain is far easier if a baseline ECG is available. One single ECG trace is therefore a useful investigation for everyone, before starting treatment.

After onset of suspicious chest pains, an ECG is essential. I have been diagnosed with high BP. What tests and investigations will be done to find out why I have this?

Before starting treatment, everybody should be tested for possible kidney damage by simple urine tests for protein, bacteria and glucose, and by measuring blood urea and creatinine levels. These may indicate a cause for your high BP in your kidneys; this accounts for more than half of all cases of classical secondary high BP. At the same time a number of other routine blood tests are usually requested, including three that often give clues to high alcohol intake (raised mean corpuscular volume, gammaglutamyl transferase and triglyceride levels), and one that indicates rare adrenal tumours that raise BP (reduced blood potassium).

Routine chest X-rays and special X-rays of the kidney (‘pyelography’) were thought at one time to be essential before starting treatment. Many trials have since confirmed that these are not efficient ways of looking for secondary high BP at this stage, unless there are other definite indications of heart failure, lung or kidney disease.

If, after several months of treatment, your BP is not controlled or, if after several years of good control, your BP becomes uncontrollable despite continued treatment, a secondary cause will be sought, starting with investigations to see whether one of your kidney arteries has been blocked by a clot. Some very rare causes, such as the adrenal tumour phaeochromocytoma, are extremely difficult to find.

Will my visit to the clinic be the only one I have to attend?  How many readings and visits are needed before high BP is diagnosed?

There is no universally accepted number of visits that are necessary to establish a diagnosis of high BP. However, all national guidelines recommend several visits and several readings before high BP is diagnosed. Clinical trials that established the benefits of BP-lowering treatments generally used two or three BP readings on three or more clinic visits to establish the diagnosis.

I am aged 74 and have recently been told that I have high BP. During the initial consultation my doctor showed me a chart and told me that my cardiovascular risk was high. What does all this mean?

Guidelines now state that high BP should not be seen and treated on its own without also taking into account your risk of suffering a stroke or heart attack). Factors such as age, gender, history of diabetes, smoking status, serum cholesterol, family history and past history of possible strokes and heart attacks, all contribute to your level of cardiovascular risk.

Charts that rank people into levels of such risk have now been published and can be found on the National Heart Foundation of New Zealand’s website: www.nzgg.org.nz/library/gl_complete/bloodpressure/table1.cfm, and many general practitioners use these charts. 

A consequence of taking this type of approach is that treatment recommendations are likely to include non-drug solutions, such as taking more exercise or stopping smoking. It also means that different types of drug treatments can also be recommended, such as cholesterol-lowering drugs, BP-lowering drugs and drugs that prevent clotting (aspirin).

Some pointers as to your risk, such as age and gender, are not possible to change. Getting older is associated with an increasing risk of suffering a heart attack or stroke. Your decision of whether to start or defer treatment is very much up to you.

Discussion with your doctor and nurse about taking BP-lowering drugs should be in the light of your overall risk, whether you wish  to try non-drug treatments initially, and whether you are happy to take BP-lowering drugs (putting you at risk of suffering side effects) to lower your initial risk of stroke or heart attack. Some people find it helpful to consider their actual level of risk and their risk compared with an average person of their age and sex.

How do I decide to start treatment or not, based on my absolute risk of suffering a heart attack or stroke?

Absolute risk profiles and risk-based guidelines do not by themselves solve the problem of setting treatment starting points (‘thresholds’). Blood pressure treatment guidelines often specify different treatment thresholds for starting BP-lowering drugs, and it is well known that people seeking help and health professionals differ in the threshold that they would choose themselves for starting to take BP-lowering drugs.

As there is a direct, linear relationship between systolic and diastolic BP and the risk of future heart attack or stroke (the higher your BP, the greater your risk), it is not surprising that there is no strong agreement as to which BP or absolute risk threshold should be chosen when deciding on BP-lowering treatment. For this reason, you should discuss with your doctor what level of absolute risk you think is acceptable before starting BP-lowering drugs. Some people find it helpful to consider their risk in the context of their absolute risk compared with somebody of the same age and sex.

If all this seems confusing, there are now several charts, CD-ROMs and websites that help you to weigh up the risks and benefits of BP-lowering drugs. You need to balance up the future potential benefit of starting BP-lowering drugs weighed against possible side effects and inconvenience of taking long-term treatment. Your doctor will also want to weigh up costs.

Aside from these risk charts, are there any other ways to estimate my cardiovascular risk?

Risk estimation can now be undertaken on the internet using information derived from trials of BP-lowering drugs therapy. These websites often contain information about drug and non-drug treatment of high BP.

Research has shown that people with high BP often disagree with BP guidelines and health professionals over the level of risk that they are prepared to accept as either safe or hazardous. You should view your risk assessment and BP level as the starting point for discussing the risks and benefits of BP treatment with your doctor or practice nurse.

Though it can be confusing and intimidating at first, your own preferences about taking medication and about the consequences of high BP, particularly how you feel about avoiding a stroke or a heart attack, are the most important factors when you are trying to decide whether or not you wish to start taking BP medication.

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