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What you need to know about hypertension

GP cardiovascular expert Dr Alex Watson answers GP Dr Kathryn Griffith’s questions on initial investigations, whether there’s still a role for ß-blockers and whether to use the newest drug, aliskiren

GP cardiovascular expert Dr Alex Watson answers GP Dr Kathryn Griffith's questions on initial investigations, whether there's still a role for ß-blockers and whether to use the newest drug, aliskiren

1) Which patients should we investigate for an underlying cause of hypertension?

41221232At least 80% of patients with hypertension will have no identifiable underlying cause. Nevertheless, all patients with a sustained untreated blood pressure higher than 140/90 should have basic investigations carried out in the practice, including blood for creatinine, urea and electrolytes, plus glucose (ideally fasting), lipids (ideally fasting) and urine tested for protein/blood as well as a resting 12-lead ECG. This may help in identifying the minority of patients with underlying causes.

For example, a raised creatinine and proteinuria might suggest a renal abnormality and electrolyte abnormalities (low potassium and raised sodium) could indicate Conn's syndrome (benign adrenal adenoma). Patients presenting with highly variable BP and facial flushing – which might suggest an underlying phaeochromocytoma – would need 24-hour urinary catecholamine estimation.

These patients would normally be referred for specialist investigation, as should: those aged under 30; patients with resistant hypertension despite being compliant on adequate doses of three antihypertensive drugs; and those who present with sudden worsening of their BP.

Investigations such as renal imaging, CT adrenal scanning, MRI of renal arteries, measurement of plasma renin and aldosterone and other tests would be available to the hospital specialist.

2) Is an ECG and/or a chest X-ray useful at diagnosis?

As mentioned above, a 12-lead ECG is an essential component of the diagnostic workup of the patient newly presenting with hypertension. ECG changes suggestive of left ventricular hypertrophy (LVH) will alert to hypertension end organ damage and should lower the threshold for treating these patients with drugs.

Normally, with no evidence of end organ damage (or diabetes, established vascular disease and 10-year CV risk greater than 20%) the threshold for drug treatment would be a sustained BP over 160/100. In those patients with end organ damage, that threshold should be lowered to 140/90.

A chest X-ray lacks sensitivity in identifying LVH and therefore is not useful at diagnosis. Echocardiography, although the ‘gold standard' test for LVH, is not cost-effective in assessing hypertensive patients.

The resting ECG may also show other abnormalities, including unidentified ischaemia, which would be another reason for referring the newly diagnosed hypertensive to secondary care.

3) When should 24-hour BP monitoring be used to make a diagnosis – and when is it helpful in monitoring patients?

In an ideal world, all newly diagnosed hypertensives, particularly those near the threshold for treatment, should have ambulatory BP monitoring. It is extremely useful when ‘white coat' BP is suspected and might obviate the need for unnecessary treatment. Some patients have marked BP variability when measured in the surgery and ABPM will properly classify their BP and guide treatment decisions.

In the established hypertensive, ABPM monitoring is useful in patients whose BP is not to target despite compliance with adequate doses of three classes of antihypertensive drugs. It also helps to see if patients are being overtreated when they complain of dizziness.

Finally, since clinic readings are by and large meaningless in patients with known white coat hypertension, then ABPM or self blood-pressure monitoring (SPBM) are the only way to adequately monitor these patients.

4) If most patients need more than one drug to control blood pressure, should we ever start with a combination product? Is it more logical to increase an individual drug to its maximum dose or to add in more drugs?

As you suggest, if most patients are going to require combination therapy, then there is a powerful argument for starting it from the beginning. There is quite good evidence – particularly from the VALUE study – that patients who achieve blood pressure control earlier have better outcomes than those patients where this is more slowly achieved1. And of course patients are more likely to be concordant the fewer tablets they have to take.

But despite all this, it's important not to lose sight of the patients who can be controlled with monotherapy.

If the pre-treatment BP is near the threshold for treatment then I'd advise starting with monotherapy, perhaps switching class if target is not achieved.

In those patients whose BP is well above the threshold then use a low-dose combination treatment – particularly if this is cost neutral – and either up titrate the fixed-dose combination or add a third class if necessary.

The advantage of combining different classes of drugs – rather than using high doses of single classes – is that it reduces the risk of side-effects.

It's well known that standard doses of calcium channel blockers are less likely

to cause peripheral oedema than higher doses. Also some classes of drugs – such as ß-blockers – have a rather flat dose response curve in relation to BP lowering and most of this benefit will be achieved with standard dosing.

I think it's also intuitive to consider that if hypertension is a multifactor disorder, then using different classes of treatment in combination is likely to prove more effective than tackling this issue with single drugs alone.

5) Do you have any tips for offering lifestyle advice to improve blood pressure control?

I strongly believe that lifestyle issues underpin the good management of blood pressure and ultimately may reduce the need for some drug treatment altogether.

There are several lifestyle issues that directly impact on BP: being overweight, a sedentary lifestyle, drinking alcohol beyond the recommended limits, and a salty diet.

My tip would be to tackle each of these areas a bit, rather than concentrating on one lifestyle issue alone. So I recommend patients try to take a little bit more exercise regularly, get a bit of weight off and try to have some alcohol-free days, as well as trying to reduce alcohol intake to two to three drinks a day.

Cutting down on ready-prepared foods as well as cutting out added salt and cutting down on salty foods such as crisps will help. In terms of vascular health, increasing fresh fruit and vegetables and reducing the amount of saturated fats in the diet is also sensible.

6) Are there any patients who may specifically benefit from ß-blockers to treat their blood pressure or should they be fourth-line for all?

For many years ß-blockers were central to BP management. They moved down the hierarchy with the release of data from the Anglo Scandinavian Cardiac Outcomes Trial (ASCOT)2. This compared the established treatment of a diuretic and ß-blocker combination with the newer combination of a calcium channel blocker and ACE inhibitor. There were more cardiovascular events in the diuretic-ß-blocker group as well as more new cases of diabetes2. Guidelines since have stopped recommending ß-blockers as first-line treatment in favour of the ‘ACD' rule: ACE inhibitors or ARBs (A), calcium channel blockers (C) and diuretics (D) used singly or in combination3.

But ß-blockers remain ‘top of the tree' in post-MI patients and those who have heart failure or symptomatic angina. They should be prescribed in hypertensive patients with these conditions unless contraindicated, for example with reversible airways disease.

Blood pressure control is paramount and if it's well controlled on a ß-blocker-diuretic combination, there is no need to change.

7) What do you recommend for patients whose BP isn't at target and seem to be intolerant of drugs you have tried?

As we all know, drug intolerance for a relatively symptomless disorder isn't unusual. And we all have patients who are avid readers of patient information leaflets.

So a starting point has to be about communicating effectively with our patients and sharing understanding of what we're hoping to achieve in partnership – to try to reduce CV risk by reducing BP.

More than 70% of hypertensive patients are going to require at least two classes of drugs to get to target and one-third will require three or more. Patients should be told this at the outset.

Most drugs are well-tolerated, particularly if modest doses are used. Patients can be advised about side-effects that are relatively common such as oedema with calcium channel blockers and cough with ACE inhibitors. The one class of antihypertensive agents with a side-effect profile akin to placebo are the ARBs.

So if all else fails and the patient seems intolerant to much, it may be worthwhile revisiting this class – perhaps using another drug from within the class if the patient has been intolerant of one previously.

Use a low dose initially and increase to a moderate – though not high – dose before attempting to introduce another drug.

Start low and go slow – patience and persistence often succeeds.

8) Aliskiren is the first in a new class of drugs, the renin antagonists. When would you consider using it?

Like all new drugs, this class will not be a first-line therapy. For now I feel it should be reserved for specialist use until its place in treatment protocols becomes clearer. It is likely to be used in situations where patients are allergic to, or intolerant of, both ACE inhibitors and ARBs when blockage of the renin-angiotensin-aldosterone system remains important.

It may also be combined with these drugs in high-risk patients – such as those with diabetes – whose BP cannot be otherwise controlled. But in these cases there will have to be close monitoring for hyperkalaemia. So I think it's still a ‘wait and see' policy while specialists use this new class of drug in difficult-to-treat hypertensive patients.

9) I sometimes have patients sent back to me from pre-op assessment clinics because their blood pressure is "too high for surgery". Yet these levels may not always warrant long-term treatment. How should these patients be managed ­ and are they the GP's responsibility or the anaesthetist's?

We need to consider the reason for surgery. It seems sensible that if the problem is serious ­ or distressing for the patient ­ and the need for surgery is urgent, it's clearly the anaesthetist's responsibility to manage that patient's BP.

Not infrequently, though, we're asked to review the patient's BP. Some patients are anxious waiting to see a hospital specialist and of course anxiety can temporarily raise BP. If surgery is routine and can be postponed then we can consider that the anaesthetist has screened our patient and identified an issue that we need to follow up.

We should then apply our practice protocol for assessing and investigating these patients in-house before returning these patients to the specialist with BP controlled to target or with a diagnosis of white-coat hypertension.

10) What's the role of patient self-monitoring of blood pressure?

I think this is the way forward in managing hypertension. Our patients are increasingly buying semi-automatic devices and we as GPs should be using these devices more often to improve BP information. It's also a great aid to concordance.

There are now quite good rules as to how to self-monitor BP and interpret results.

Generally, suitable patients, once taught, should use the first day at home to familiarise themselves with BP recording then over the next six days record BP twice in the morning and twice in the evening. All these readings are simply averaged.

A correction factor of adding 10mmHg to the systolic BP and 5mmHg to the diastolic BP should be made. This is in recognition that home readings will always be lower than in those clinic settings. Unless we do that we'll underestimate risk based on home readings alone.

So an average SBPM of 152/96 would be corrected to equate to a clinic average of 162/101. This particular patient would need their BP treated.

This area of BP recording is advancing rapidly and perhaps in the future patients will feed their self-recorded BP information into the practice by telemetry allowing speedy and informed decision making.

The indications for SBPM are exactly the same as those for ABPM.

11) Which patients should be referred to specialist clinics?

The availability of evidence-based hypertension protocols mean most patients can be managed entirely in primary care but certain cases merit specialist attention.

At initial assessment, are the pressures very high (above 220/120 sustained)? Is there retinopathy? Patients with accelerated hypertension should be referred. So should people aged less than 30 as they are more likely to have secondary hypertension and require detailed investigation.

Refer patients in whom immediate control of BP is crucial because of impending problems such as new-onset TIA or heart failure, all pregnant women and arguably women who are planning pregnancy.

Also, does your initial investigation reveal an underlying problem, such as unexplained high creatinine? Does the patient have symptoms that may suggest secondary hypertension, such as flushing in a young hypertensive man (possible phaeochromocytoma)?

Finally, consider for referral patients in whom BP control has proved difficult, those with multiple drug intolerance and those with resistant hypertension (defined as those on three classes of drugs whose BP is not below 140/90).

Once investigated and treated, though, there is little reason for these hypertensive patients to be followed up in specialist clinics as they can normally be looked after in primary care ­ often in nurse-led follow-up clinics.

Dr Alex Watson is a GP in Dundee and honorary senior lecturer at the department of general practice, University of Dundee, and clinical assistant at the cardiovascular risk clinic, Ninewells Hospital Dundee

Competing interests Dr Watson has received lecture fees and sponsorship to meetings from Pfizer, Novartis and Boeringer Ingelheim

What I Will Do Now What I Will Do Now

Dr Kathryn Griffith considers the responses to her question

I'll review the practice protocol for hypertension. The important issues at diagnosis are to identify underlying causes of hypertension and evidence of target organ damage on an ECG, not chest X-ray.
The next step is to determine the presence of sustained BP and the threshold for treatment, which differs with high CV risk.
The choice of first-line agent should follow BHS guidelines – however, ß-blockers may be first-line for patients with ischaemic heart disease or heart failure.
It's interesting to read of evidence that patients who control BP earlier do better.
And it's worth bearing in mind some agents – such as spironolactone – take time to achieve their full effects. It is important to review patients monthly until they reach target BP.
I'll review advice about titrating all drugs to optimal doses to reduce side-effects, thereby improving concordance.
I shall continue to recommend patients buy a semi-automatic sphygmomanometer to improve assessment of BP control.
It's important not to forget the benefits of lifestyle management.
Dr Kathryn Griffith is a GP in York

thps Automated sphyg

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