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Hypertension management: can we do better?

GPs are faced with two important new guidelines on hypertension, parts of which conflict – Professor Peter Sever examines the practical implications for managing patients

Every year about 200,000 people die of CHD or stroke in the UK. Some 20 per cent of these are due to raised blood pressure and half of these could be avoided with better BP control. We need to do better.

Recent meta-analyses of different antihypertensive treatment strategies show cardiovascular events can be reduced by about 20 per cent, CHD events by 20 per cent and strokes by 35 per cent. In high-risk patients small reductions in BP are associated with large absolute reductions in fatal and non-fatal events.

Yet patients usually do far worse in clinical practice than they do in clinical trials. In the latest Health Survey for England, 36 per cent of the population were aware their blood pressure was raised, 25 per cent of known hypertensives were treated, of whom just 40 per cent were controlled to today's targets of 140/90mmHg or below.

In other words, only about 10 per cent of all UK hypertensives are controlled. Comparable figures for a number of other countries are shown in the figure on the right.

Rationale for ABCD

So why has BP control been so poor? Previous guidelines have been elaborate and at times inconsistent. Moreover, practical treatment strategies were not made clear. We often blame patients for poor compliance with treatment, but there is a wealth of evidence of therapeutic inertia. Faced with patients whose BP remains above targets levels, physicians frequently make no attempt to increase drug dosage, switch or add-on drugs to reach BP goals.

Against this background, the British Hypertension Society guidelines have developed simple, pragmatic algorithms to help doctors manage hypertensive patients in clinical practice. These guidelines advocate the ABCD algorithm, based on the following principles:

lAll the drugs recommended have been shown to reduce cardiovascular events in randomised controlled trials by approximately the same amount

lBP control is paramount, but some drugs are more or less effective in certain patient sub-groups

lMany studies have shown that renin status influences responsiveness to different drugs

lThe elderly and those of African origin tend to have low renin levels.

The BHS therefore recommends the initial choice of drug is determined by age and ethnicity, with younger Caucasian hypertensives (who tend to have higher plasma renin levels) starting on an angiotensin converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) or a ß-blocker, and with older or Afro-Caribbean patients who have lower renin levels, starting on a calcium channel blocker or a diuretic. Failure to control pressure with initial therapy is followed by the addition of a drug from the alternative group: A or B + C or D.

Where there is no additional factor to consider, costs should be taken into account in selecting the drugs. On the question of dose, wherever possible the drug or formulation should be effective for 24 hours when taken once daily. Drug doses should be titrated up according to the manufacturers' instructions to the highest well-tolerated dose in striving to achieve blood pressure goals.

In the case of thiazide diuretics it remains unproven whether very low doses – bendrofluazide 2.5mg daily or hydrochlorthiazide 12.5mg daily, for example – are as effective as higher doses (such as 5mg and 25mg respectively), although at the higher doses adverse metabolic effects are more common.

The BHS guidelines include (B) in parenthesis to emphasise that some recent trials have reported an increased incidence of diabetes in patients treated by B and/or D drugs when compared with A or C drugs, particularly when B and D are combined. In those at high risk of developing diabetes it is advised that they should not be routinely used. However, more data is required and may become available when the final results of the ASCOT trial are reported (see box, page 60).

BHS and NICE

Both BHS and NICE address many aspects of hypertension management, and the final draft version of NICE shows a high degree of consistency with the BHS. For example, both guidelines emphasise the importance of lifestyle modification, which may not only lower blood pressure but may also reduce the future risk of coronary heart disease (see box top left). Both also provide similar recommendations on BP measurement in hypertensives (see lower box).

But there are two big differences between the guidelines. First, NICE omits significant reference to the need to address overall cardiovascular risk in the hypertensive subject and the substantial benefits to be gained in the majority of hypertensive patients by multiple risk factor intervention, particularly from statins.

To put this into context, there is a greater likelihood of preventing a coronary event in a hypertensive person by lowering cholesterol than by lowering BP. Of course, in many patients both are indicated. NICE, in a 249-page document, includes just a single sentence on consideration of lipid lowering in high-risk patients. BHS deals comprehensively with this important issue.

Second, NICE declines to endorse the ABCD rule on the grounds that:

lIt has not been explicitly tested in outcome trials

lOutcome trials do not provide evidence of age-related benefits of particular drugs – such as A/B for the young and C/D for the old

lCost-effectiveness has not been taken into account.

In response to these points it must be pointed out that more than a dozen outcome trials, either completed or ongoing, have adopted the ABCD principle. The effectiveness of BP reduction in these trials, which is clearly related to outcome, is sound evidence that the rule works. To achieve blood pressure goals with inappropriate combinations of drugs is more difficult, requires more patient visits and assessment, is often unsuccessful and exposes hypertensives to continuing cardiovascular risk – a situation commonly encountered in everyday practice.

A wealth of data supports the claim that antihypertensive efficacy is influenced by renin status and that low-renin patients respond less well to ß-blockers, ACE inhibitors and ARBs than to diuretics or calcium channel blockers.

Commencing patients on less-effective drugs leads to more patient visits involving dose titration, switching drugs and add-on therapy, which all have cost implications.

Basing choice simply on the cost of the tablet gives an incomplete and often incorrect assessment of cost-effectiveness. Health economic analyses following the outcome of ASCOT will provide further information on this important issue.

Conclusion

The BHS and NICE guidelines – together with other national and international guidelines – are presented against the background of the worldwide epidemic of cardiovascular disease, including coronary heart disease and stroke, and the recognition that blood pressure is one of the most important risk factors contributing to this epidemic.

To date the implementation of prevention and treatment strategies for hypertension-related CVD have been largely unsuccessful. Using the now widely accepted definition of hypertension as a blood pressure in excess of 140/90mmHg, 30-40 per cent of men and women meet these criteria.

CHD and stroke morbidity place enormous burdens on individuals and society, and similar improvements would be an inevitable consequence of better blood pressure control.

Every three or four years guidelines on the management of hypertension in clinical practice have been updated in the light of new evidence, largely based on randomised controlled clinical trials and prospective observational studies.

New analyses of epidemiological observations on the association of blood pressure and CVD events have focused on the overriding importance of systolic pressure as a predictor of CHD and stroke. Such is the importance of these observations that all guidelines now emphasise the need to control systolic pressure in any treatment strategy.

It is to be hoped ongoing discussion between stakeholders and NICE will eventually lead to guidelines that are in large measure consistent and offer clear and unambiguous messages to practising clinicians.

In the absence of consistency, attempts to improve outcome for hypertension will be seriously compromised and the UK will continue to lag behind Europe and the USA in the quality of blood pressure management, while cardiovascular morbidity and mortality related to poor BP control will remain a serious problem.

Peter Sever is consultant in clinical pharmacology, International Centre for Circulatory Health and Imperial College, London – he is a member of the British Hypertension Society Guidelines Committee and an invited referee of the NICE guidelines

Lifestyle and hypertension

lReducing sodium intake to <6g per="" day="" will="" lower="" systolic="" and="" diastolic="" bp="" by="" about="" 3mmhg="" in="" hypertensive="" patients;="" in="" about="" one-third="" of="" these="" patients,="" higher="" reductions="" of="" around="" 5/5mmhg="" can="" be="">

lA combination of diet, physical exercise and weight reduction may lead to similar reductions in BP, with larger reductions reported in some trials

lIn epidemiological studies there is a clear relationship between body weight and BP

lIn obese patients, the greater the weight loss the greater the fall in BP

Source: BHS, NICE

BP measurement in hypertension

lIn general, at each visit two or possibly three readings should be obtained rather than a single value, which may be unrepresentative of a patient's usual BP

lAfter initiating treatment, BP should normally be repeated at four-six weekly intervals when opportunities may be taken to alter dose or change treatment

lWhen good control is achieved, visits may be arranged at three-four monthly intervals

lClinic nurses play an important role in routine follow-up

Source: BHS, NICE

The Anglo Scandinavian Cardiac Outcomes Trial (ASCOT)

recruited more than 19,000 uncontrolled hypertensive subjects with additional cardiovascular risk factors. More than 9,000 of these were from primary care practices in the UK.

Most were already on treatment for hypertension, yet their average BP at randomisation was 164/95mmHg. By implementing simple but pragmatic treatment-to-target algorithms this was reduced to 139/81mmHg – that is by 25mmHg systolic and 14mmHg diastolic over a three-year follow-up period. By years four and five BP had fallen even further.

These observations clearly demonstrate that in most patients there is nothing resistant to treatment.

The principles of the ABCD rule are incorporated into the first two steps of the ASCOT trial; over 80 per cent of patients reach step two and beyond and excellent blood pressure control has been achieved.

The two key messages are therefore:

lTreat to target

lUse simple, pragmatic algorithms to help achieve goals.

References

1 Wolf-Maier K et al. Hypertension treatment and control in five European countries, Canada and the United States.

Hypertension 2004; 43:10-17

2 Sever P et al. Rationale, design, methods and baseline demography of participants of the Anglo-Scandinavian Cardiac Outcomes Trial. J Hypertens 2001;19:1139-47

3 Sever P et al. Prevention of coronary and stroke events with atorvastatin in hypertensive patients who have average or lower-than-average cholesterol concentrations, in the Anglo-Scandinavian Cardiac Outcomes Trial – Lipid Lowering Arm (ASCOT-LLA):

a multicentre randomised controlled trial. Lancet 2003;361:1149-58

Further information

British Hypertension Society. Guidelines for Hypertension Management. BMJ 2004, in press

NICE. Essential Hypertension:

Managing Adult Patients in Primary Care: Final Consultation Draft. www.nice.org.uk/docref.asp?d=103326

Blood Pressure Lowering Treatment Trialists' Collaboration. Effects of different blood-pressure-lowering regimens on major cardiovascular events: results of prospectively designed overviews of randomised trials. Lancet 2003; 362: 1527-35

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