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The clash between the advice of the British Hypertension Society and NICE needs sorting, says Dr Jonathan Morrell in the meantime he proposes a route through the maze

Blood pressure remains key to reducing overall cardiovascular morbidity and mortality. Getting blood pressure down has been recommended for decades but the proportion whose high blood pressure is reduced below target levels remains stubbornly low. There are three reasons for this:

-too few patients with high blood pressure are identified

-too few of those identified are treated

-too few of those treated are treated effectively.

The GMS contract provides a clear incentive for GPs to control blood pressure.

But at the same time GPs have also been confused by new guidelines from the National Institute for Clinical Excellence and the British Hypertension Society (see boxes 1, 2 and 3) because of the different emphases they put on the treatments that should be used. Which should the GP follow?

The conflict

Before we go into the areas of conflict, I want to point out that NICE and the BHS are in broad agreement about many things.

-Both suggest that if a patient's blood pressure is 140/90mmHg, then they should normally be treated if they have (as is likely) an overall 10-year cardiovascular risk of more than 20 per cent (box 4, page 55).

-They are also agreed that there is a spectrum of risk rather than a single cut-off point and that even above 130/85mmHg patients have a higher than optimal blood pressure. Those with such 'high normal' blood pressures should be monitored at least annually and receive lifestyle intervention.

-Both specify stricter targets for those with diabetes (<130>

GThey agree that those needing drug treatment are likely to need at least two, and often more, therapeutic agents for their blood pressure to be adequately controlled. Combination treatment is now regarded as the norm in routine clinical practice. The BHS guidelines go so far as to blame an overreliance on monotherapy as an important cause of current poor rates of hypertension control.

But it is in selecting which treatments to use where the two guidelines unfortunately differ. The BHS has developed the so-called AB/CD system based on the impact of four groups of antihypertensive agents in patients broadly classified according to their renin levels: A ACE inhibitors or angiotensin receptor blockers (ARBs); B -blockers;

C calcium channel blockers; and

D diuretics. In patients under 55, the BHS suggests starting with an agent from the A or B class, escalating to a combination with C or D (but avoiding the B+D combination) and then using an A+C+D combination if two agents are ineffective.

BHS caution regarding the B+D combination stems from data from recent outcome trials, such as LIFE1, which reported more new-onset diabetes in trials of -blockers and diuretics, especially when the two are combined. NICE does acknowledge this but its 'headline' advice is still to start treatment with a low-dose thiazide diuretic, adding in a -blocker if necessary.

NICE cautions that the B+D combination should be avoided in those at increased risk of new-onset diabetes: those with a family history, a high fasting plasma glucose (FPG>6.5mmol/L), a BMI of 30 or more, or of south Asian or African-Caribbean origin.

The finding that younger patients achieve target better with A or B regimes supports the BHS algorithm. The recent VALUE trial2 additionally supports the C+D combination in older patients. The recently published Effective Health Care review of the effectiveness of antihypertensive drugs in black people again endorsed the value of the C+D BHS approach.

The biggest disagreement

What is most at odds between the two sets of guidelines is the place of ACE inhibitors and ARBs, which play a more prominent role in the BHS advice. ACE inhibitors and ARBs, according to NICE, are part of a recommended 'stepped care' approach to hypertension which urges rapid escalation of treatment to reach blood pressure control.

But the BHS suggests using ACE inhibitors and ARBs in a series of 'compelling indications' including heart failure, cerebrovascular disease, coronary disease and diabetes supported by recent clinical trials and involving a sizable proportion of patients with high blood pressure.

One reason for the difference in approach is NICE's failure to evaluate endpoints beyond death, MI and stroke and take into account so-called secondary endpoints such as emergent diabetes, reduced left ventricular mass or improvements in endothelial function.

Added benefits from choosing particular drug groups

The place of ACE inhibitors in the BHS guidance looks to evidence from a series of trials, outlined in box 5, that suggests blocking the angiotensin converting enzyme may have benefits beyond blood pressure lowering.

These effects may include improving endothelial function and reducing atherosclerotic progression one reason patients who already have coronary heart disease should usually be on ACE inhibitors.

Since the publication of the guidelines, new research has added to previous findings suggesting ACE inhibitor treatment has endothelial and anti-atherosclerosic benefits.

The PERTINENT trial details6, which were presented at the 2004 meeting of the European Cardiology Society, found significant anti-plaque and anti-clotting effects in patients with coronary disease treated with perindopril, suggesting real mechanisms why ACE inhibition may have effects beyond blood pressure lowering.

Evidence such as this is likely to mean that, in time, guidelines will need updating to reflect the growing evidence that the way blood pressure is lowered can have an added benefit beyond falls in pressure alone. For now, both sets of guidelines emphasise that blood pressure control is a vital part of cardiovascular risk reduction in primary care, particularly in the significant patient population with established cardiovascular risk such as diabetes or other risk factors.

Blood pressure control reduces the likelihood of strokes and myocardial infarction, and so prevents disability, dependency, cognitive decline, stroke-related dementia, and heart failure. BP control also maintains quality of life in patients.

Going beyond the contract

The 'rule of halves' still very much applies to the primary care management of hypertension. As a result, 158 clinical points have been made available in the new GMS contract for the management of hypertension in primary and secondary prevention specifically to improve care.

But there is a clear element of dumbing down as a result of the new contract's soft targets (<150 0mmhg="" and=""><145 5mmhg="" in="" diabetes)="" and="" low="" maximum="" thresholds="" (70="" per="" cent="" and="" 55="" per="" cent="" in="">

NICE and BHS targets are lower, particularly in renal disease and diabetes mellitus, and therefore the contract will fall short of the outcome event reduction seen in the clinical trials on which the more 'official' guidelines are based.

The GMS contract is likely to become the dominant 'guideline', leaving GPs with a choice whether to settle for the easier GMS targets which will be just enough to gain the necessary points, or to aim for the more difficult BHS/NICE targets which potentially offer so much more to patients.

Coming to your decision

The key to treatment for most patients is using at least two, possibly more, treatments and the BHS recommends its AB/CD algorithm, which is pragmatic, rational

and easy to remember. In a busy general practice its simplicity makes it an attractive option.

Taking into account that compelling indications for ACE inhibitors/ARBs are present in a sizeable proportion of hypertensive patients, this class may be preferred in most of them.

The frequency of diabetes and pre-diabetes states in the population makes initiation on diuretics and -blockers, as NICE suggests, of some concern. As a consequence, the A+DC combination appears to be required for most hypertensive patients.

It is a decision for each practice and each GP whether to follow either of these new guidelines. But we must focus first on the clinical need to reduce blood pressure as effectively and safely as we can.

The AB/CD protocol offers us a way of treating patients effectively according to a system that can be applied across the whole practice.

NICE may not be wrong, but the AB/CD protocol is likely to be more right for many practices.

Jonathan Morrell is a GP in Hastings, East Sussex, and a hospital practitioner in cardiology he is founding trustee and director of HEART UK and a member of the British Cardiac Society

Tailoring therapy

Most people require more than one drug to control their blood pressure, and treatment algorithms such as AB/CD achieve better BP control than routine clinical practice, according to the BHS.

The algorithm is based on the idea there are high-renin and low-renin types of hypertension and that treatments that affect the renin angiotensin system

(A or B) are more effective in younger (under 55) non-black patients with higher renin concentrations.

Those with lower renin concentrations, and older and/or black patients, are recommended C and D therapies.

Fixed dose combinations, which used to be frowned on by specialists but used by GPs, are now welcomed to reduce the number of tablets patients take.

Treatments that can be given once daily are preferred and are likely to improve rates of compliance.

Who to treat?

-Blood pressure over 180/110mmHg = treat immediately

-Blood pressure over >160/100mmHg on repeated occasions over 4-12 weeks

-BP >140/90mmHg on repeated occasions plus end organ damage or 10-year cardiovascular risk >20% (reassess yearly if no complications, diabetes or cardiovascular risk <>

Note: those with blood pressure 130-139/85-89mmHg should be screened annually while those <130 5mmhg="" should="" be="" reassessed="" every="" five="">

Trials that show what else

ACE inhibitors can do

The HOPE trial3 established ACE inhibition with ramipril as a reducer of risk of cardiovascular death, MI and death in patients at high cardiovascular risk.

EUROPA4, a study of patients with coronary artery disease of differing severity, approximating more closely than many trials to the 'real-life' clinical population, found a fall in the number of cardiovascular events for patients taking perindopril greater than that expected from blood pressure falls alone.

EUROPA's diabetes sub-study found the same relative benefit, but a greater absolute benefit, in patients with diabetes5.

What our other authors said about the guidelines

Professor Graham MacGregor, professor of cardiovascular medicine, St George's Hospital Medical

School, London

'The NICE guidelines were driven by cost considerations and not by the effect on the individual with high blood pressure or necessarily the benefits in outcome. This meant that throughout the guideline process, drug therapy was focused on the use of betablockers and diuretics.

'There are some important errors in the NICE guidelines: first, the usefulness of individuals measuring their own blood pressure is dismissed. There is also an overemphasis on stress relaxation, which has little role to play in the management of high blood pressure.

'And while they recommend a reduction in salt intake, they do not recommend any increase in fruit and vegetable consumption, despite the plethora of studies showing the benefits of potassium on lowering blood pressure.'

Dr Parthasarathy Hari Krishnan,

clinical research fellow in cardiovascular medicine, and Professor Tom MacDonald, professor of clinical pharmacology and pharmacoepidemiology, Ninewells

Hospital and Medical School, University of Dundee

'Many feel the rigorous approach of BHS will substantially increase NHS workload but others feel NICE guidelines do not provide optimum care.

'There are discrepancies between the guidelines on advice regarding lifestyle. The BHS advises weight reduction, the Dietary Advice to Stop Hypertension (DASH) eating plan, dietary sodium restriction, increased physical activity and alcohol moderation. NICE does not advise the DASH eating plan, controversially suggesting that relaxation therapies are effective (although also stating that they are unlikely to be provided routinely in primary care). NICE discourages excessive caffeine-rich products (without much evidence-base to support this).'

Dr Terry McCormack, deputy chair, and

Dr Mark Davis, secretary, of the Primary Care

Cardiology Society

'The NICE guidelines consider the management

of essential hypertension. They do not consider hypertension management in patients with

different co-morbid conditions.'

References

1 Dahlof B et al. Cardiovascular morbidity and mortality in the Losartan Intervention For endpoint reduction in hypertension study (LIFE): a randomised trial against atenolol.

Lancet 2002 Mar 23;359(9311):995-1003

2 Julius S et al. Outcomes in hypertensive patients at high cardiovascular risk treated with regimens based on valsartan or amlodipine: the VALUE randomised trial.

Lancet. 2004 Jun 19;363(9426):2022-31

3 Yusuf S et al. Effects of an angiotensin-converting-enzyme inhibitor, ramipril, on cardiovascular events in high-risk patients. N Engl J Med 2000;342:145-53

4 EUROPA study investigators. Efficacy of perindopril in reduction of cardiovascular agents among patients with stable coronary artery disease: randomised, double-blind, placebo-controlled, multicentre trial (the EUROPA study).

Lancet, 2003;362:782-788

5 SoRelle R, Cardiovascular News. Circulation. 2004;109:e9028-e9030

6 www.europa-trial.org

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