Updated BHS recommendations on hypertension will aid GPs in assessing cardiovascular risk and tailoring treatment to the individual patient, says Dr Alan Begg


The British Hypertension Society has recently updated its authoritative guideline for the management of hypertension, originally published 5 years ago. The main changes are advice on the use of the AB/CD algorithm for blood pressure lowering therapy and a move towards assessing cardiovascular (CVD) rather than coronary heart disease (CHD) risk.

To remain credible, a guideline requires regular updating as the evidence base changes. Updated European 1 and North American 2 guidelines were published in 2003 but we need management recommendations that are tailored to the UK. This is important if there are variations in therapeutic licensing and available drug combinations and to ensure consistency with other national clinical guidelines.

Thresholds for intervention

The level at which a blood pressure can be safely left without need for rechecking has been reduced, from <135/85 mmHg to <130/85 mmHg. This will have the effect of increasing the group of patients with high normal blood pressure (systolic BP 130-139 mmHg/diastolic BP 85-89 mmHg) who require lifestyle change and an annual blood pressure check.

The thresholds for grade 1 mild hypertension remain at systolic BP 140-159 mmHg and diastolic BP 90-99 mmHg, with therapeutic intervention still based on the level of absolute risk. However, any patient with blood pressure sustained above systolic BP 160 mmHg/diastolic BP 100 mmHg requires treatment.

Figure 1 (below) shows the thresholds for intervention.

Figure 1: Blood pressure thresholds for intervention
http://www.nature.com/jhh/

Cardiovascular risk

Focusing on all cardiovascular events including stroke by replacing the measurement of CHD risk with CVD risk is a significant change for UK primary care.

The Joint British Societies Risk prediction charts have been modified, with individual charts for men and women, each divided into smokers and non-smokers. The four age bands are reduced to three (under 50 years, 50-59 years and 60 years and over), with systolic blood pressure and the total cholesterol:high density lipoprotein cholesterol ratio being required to determine that risk.

There are no separate charts for diabetes because a type 2 diabetes patient over the age of 50 years with hypertension will reach the suggested treatment threshold.

It is recommended that the CVD risk of a diabetes patient be regarded as equivalent to a patient without diabetes who has had a coronary event.

The CVD risk threshold of >=20% over 10 years should guide therapeutic decisions in the following situations:

  • Uncomplicated grade 1 hypertension
  • Prescribing of statins
  • Use of low dose aspirin.

Lifestyle change

Lifestyle change is an important part of helping to reduce blood pressure. The measures that can be taken remain the same with little variation in the specific advice. The following will lower BP:

  • Weight reduction, mainly by calorie restriction
  • Salt restriction, to <6 g (<100 mmol) per day
  • Limiting alcohol intake, to 21 units for men and 14 units for women
  • Increasing exercise – three sessions per week or 20 minutes walking per day, aerobic and tailored to the individual
  • Increasing fruit and vegetable consumption (at least 5 portions per day).

Cardiovascular risk (Table 1, below) can also be reduced by:

  • Stopping smoking
  • Reducing dietary fat to <=35% of total energy intake (saturated fats to <=33% of total fat intake).
Table 1: Reducing cardiovascular risk in patients with hypertension
 

High risk
Established CVD
Type 2 diabetes

Measured risk
10-year CVD risk >=20%
Statin All patients at least up to age 80
Total cholesterol >=3.5 mmol/l
All patients at least up to age 80
Total cholesterol >=3.5 mmol/l
Aspirin All patients unless contraindicated Age >50, BP controlled <150/90mmHg

Choice of therapy

The guidelines accept that the achieved blood pressure rather than the choice of therapy is the main determinant of outcome, although in certain circumstances there are compelling indications and contraindications for specific classes of antihypertensive drugs (Table 2, below).

Table 2: Compelling and possible indications, containdications, and cautions for the major classes of antihypertensive drugs
Class of drug Compelling indications Possible indications Caution Compelling contraindications
Alpha-blockers Benign prostatic
hypertrophy
- Postural hypotension, heart failurea Urinary incontinence
ACE inhibitors Heart failure, LV dysfunction, post MI or established CHD, type 1 diabetic nephropathy, 2º stroke preventione Chronic renal diseaseb, type II diabetic nephropathy, proteinuric renal disease Renal impairmentb, PVDc Pregnancy, renovascular diseased
ARBs ACE inhibitor intolerance, type II diabetic nephropathy, hypertension with LVH, heart failure in ACE-intolerant patients, post MI LV dysfunction post MI, intolerance of other antihypertensive drugs, proteinuric renal disease, chronic renal disease,b heart failure Renal impairmentb, PVDc Pregnancy, renovascular diseased
Beta-blockers MI, angina Heart failuref Heart failuref, PVD, diabetes (except with CHD) Asthma/COPD, heart block
CCBs (dihydropyridine) Elderly, ISH Elderly, angina - -
CCBs (rate limiting) Angina MI Combination with beta-blockade Heart block, heart failure
Thiazide/thiazide-like diuretics Elderly, ISH, heart failure,
2º stroke prevention
- - Goutg
COPD, chronic obstructive pulmonary disease; ISH, isolated systolic hypertension; PVD, peripheral vascular disease; LVH, left ventricular hypertrophy; ACE, angiotensin-converting enzyme; ARBs, angiotensin II receptor blockers; MI, myocardial infarction.
a HF when used as monotherapy
b ACE inhibitors or ARBs may be beneficial in chronic renal failure but should only be used with caution, close supervision and specialist advice when there is established and significant renal impairment
c Caution with ACE inhibitors and ARBs in peripheral vascular disease because of association with renovascular disease
d ACE inhibitors and ARBs are sometimes used in patients with renovascular disease under specialist supervision
e In combination with a thiazide/thiazide-like diuretic
f Beta-blockers are increasingly used to treat stable heart failure. However, beta-blockers may worsen heart failure
g Thiazide/thiazide-like diuretics may sometimes be necessary to control BP in people with a history of gout, ideally used in combination with allopurinol
Reproduced from Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV with kind permission of Nature Publishing. http://www.nature.com/jhh/

The British Hypertension Society recommends the AB/CD algorithm (Figure 2, below) to deliver better blood pressure control, to encourage logical drug combinations and to ensure best fixed drug combinations. The theory behind the use of this algorithm is that those younger than 55 years and caucasian have a high renin concentration and benefit from renin blockade (drug A or B). Drugs C and D are more effective first-line agents for older caucasian people and black people of African descent.3

Figure 2: Recommendations for combining blood pressure lowering drugs (the AB/CD rule)
http://www.nature.com/jhh/

Although most patients with hypertension will require more than one drug, the recommendations based on the algorithm have yet to show improved clinical outcomes.

On the basis of the Life Study findings which showed a significant increased risk of developing diabetes with a beta-blocker compared with an ARB,4 the guidelines advise caution in the use of the diabetogenic combination of a beta-blocker with a thiazide diuretic in those at increased risk of developing diabetes. However, the increased risk of developing diabetes using a betablocker needs to be clearly quantified.

The Ascot trial should shed light on whether this caution is justified.5 There is evidence, however, that the combination of beta-blocker and thiazide diuretic is effective in reducing the risk of cardiovascular complications, and after 9 years of follow up in the UKPDS study there were improved outcomes despite the rise in HbA1c.6

Comparing the guidelines

The European guidelines suggest that therapy should be started gradually with a single agent or low-dose combination. They note the need for certain drug doses in specific clinical situations and state that the main benefits result from blood pressure lowering, largely independent of the drugs used, with the choice tailored to the individual patient taking all factors into account.

The Second Australian National Blood Pressure trial showed a slightly better outcome in caucasian men under regimens beginning with an ACE inhibitor compared with those starting with a diuretic,7 although a recent meta-analysis suggests that diuretics are not inferior to the newer antihypertensive drugs.8

The American guidelines’ analysis2 of the ALLHAT trial suggests that diuretics are virtually unsurpassed in preventing the cardiovascular complications of hypertension and that they should be used as initial therapy for most patients with hypertension. 9

The general feeling this side of the Atlantic is that ALLHAT does not give information on the ideal combination of drugs to achieve optimum blood pressure control but that thiazide diuretics are an important class in that process in which 63% of patients required two or more drugs.10

The NICE guideline on hypertension, currently in draft form but due for publication later this year, suggests starting with a diuretic. If this fails to control the blood pressure a beta-blocker should be substituted followed by a series of treatment options.

The guidelines and general practice

Targets

On the basis of the clinical indicators of the new GMS contract, in patients with established CHD, a previous stroke/TIA or a clinical diagnosis of hypertension, any blood pressure greater than 150/90 mmHg is unacceptable. For patients with diabetes, the target to achieve is reduced to <=145/85 mmHg.

The BHS guidelines acknowledge that the new contract is likely to increase the focus on the detection and treatment of raised blood pressure and the quality of that control. The audit standard of <150/90 mmHg as a minimum target that all treated patients should attain remains. However, BHS IV recommends optimal treatment goals of <=140/85 mmHg, reduced to <=130/80 mmHg in patients with diabetes, renal impairment or established cardiovascular disease.

The role of primary care

With the increasing demands on general practice, how realistic will it be to implement this guideline fully? There is scope for structured community-based programmes to ensure that all adults up to 80 years continue to have their blood pressure measured at least every 5 years.

The workload implications for general practice to arrange annual checks in those with high normal blood pressure (systolic BP 130-139 mmHg/diastolic BP 86-89 mmHg) are significant, with a prevalence estimated at 2742 in 10 000 patients in a Scottish practice.

These individuals need to take responsibility for lifestyle change and, with evidence that home monitoring can produce better outcomes, perhaps for the monitoring process as well.11

Evaluating patients with raised blood pressure, initiating therapy and monitoring those with established hypertension with or without diabetes and target organ damage, is the responsibility of the primary care team under the new contract’s quality and outcomes framework.

The polypill and over-the-counter drugs will not ensure that those with most to gain will be treated appropriately. For successful implementation, new ways of delivering healthcare with extended roles for members of the multidisciplinary practice team need to be considered.

  • Guidelines for management of hypertension: report of the fourth working party of the British Hypertension Society, 2004-BHS IV is published by the Journal of Human Hypertension (J Hum Hypertens 2004; 18: 139-85).

References

  1. European Society of Hypertension-European Society of Cardiology Guidelines Committee. 2003 European Society of Hypertension- European Society of Cardiology guidelines for the management of arterial hypertension. J Hypertens 2003; 21: 1011-53.
  2. Chobanian AV, Bakris GL, Black HR et al; National Heart, Lung, and Blood Institute Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; National High Blood Pressure Education Program Coordinating Committee.The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 report. JAMA 2003; 289: 2560-72.
  3. Brown MJ, Cruickshank JK, Dominiczak AF, MacGregor GA, Poulter NR, Russell GI et al. Executive Committee, British Hypertension Society. Better blood pressure control: how to combine drugs. J Hum Hypertens 2003; 17: 81-6.
  4. Dahlöf B, Devereux RB, Kjeldsen SE et al. LIFE Study Group. Cardiovascular morbidity and mortality in the Losartan Intervention For Endpoint reduction in hypertension study (LIFE): a randomised trial against atenolol. Lancet 2002; 359: 995-1003.
  5. Sever PS, Dahlöf B, Poulter NR et al. Rationale, design methods and baseline demography of participants of the Anglo-Scandinavian Cardiac Outcomes Trial. ASCOT investigators. J Hypertens 2001; 19: 1139-47.
  6. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes. UKPDS 38. UK Prospective Diabetes Study Group. Br Med J 1998; 317: 703- 13.
  7. Wing LM, Reid CM, Ryan P et al. Second Australian National Blood Pressure Study Group. A comparison of outcomes with angiotensinconverting- enzyme inhibitors and diuretics for hypertension in the elderly. N Engl J Med 2003; 348: 583-92.
  8. 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: 1527-45.
  9. The ALLHAT Officers and Coordinators for the ALLHAT Collaborative Research Group. Major outcomes in high risk hypertensive patients randomised to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic. JAMA 2002; 288: 2981-97.
  10. Williams B. Drug treatment of hypertension. Br Med J 2003; 326: 61-2.
  11. Bobrie G, Chatellier G, Genos N. Cardiovascular prognosis of "masked hypertension” detected by blood pressure self-measurement in elderly treated hypertensive patients. JAMA 2004; 291(11): 1342-9.

Click here for a checklist to aid implementation of the British Hypertension Society's guidelines for the management of hypertension, which you can print out and keep

 

Guidelines in Practice, May 2004, Volume 7(5)
© 2004 MGP Ltd
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