Hypertension is a well-known risk factor for cardiovascular disease (CVD) and management of high BP is an important element of primary prevention. It can, however, be difficult to know when to initiate treatment and, with so many drugs available, what that treatment should entail.
1. Interpreting a reading
In a patient without diabetes, hypertension is diagnosed with three readings >140/90mmHg, taken over six to 12 weeks. Medication should be considered for persistent hypertension and is recommended in anyone with a repeated BP >160/100mmHg (systolic or diastolic reading, or both), regardless of age, race or sex.
Where BP is 140-159/90-99mmHg, routine blood tests for renal function, fasting glucose and cholesterol, and a urine dip for microalbuminuria should be performed, and a Q-risk score calculated.
Patients with diabetes, those with reduced renal function or with a Q-risk score ≥20 per cent over 10 years should also begin treatment. Lifestyle modification alone is recommended for cases not reaching the pharmaceutical treatment threshold and for those with borderline high BP (>130/85mmHg), with regular ongoing monitoring.
2. Treatment targets
A target of 140/85mmHg should be used for most patients. In those with diabetes, known CVD or chronic renal failure 130/80mmHg is the target. In patients with diabetes, tight glucose control is vital and in all hypertensive patients, ongoing attention should be paid to modification of other risk factors.
3. Initiating treatment
In the absence of contraindications, NICE has outlined two main management strategies (the updated NICE guidelines are due for completion in August 2011).1
In those aged below 55 years of age and not of Afro-Caribbean race, an ACE inhibitor (or ARB if the ACE inhibitor is not tolerated) is recommended first-line. If this fails to control the hypertension a thiazide diuretic or calcium channel blocker should be added to the first-line medication. If hypertension remains poorly controlled then both a thiazide diuretic and a calcium channel blocker should be used with the first-line medication.
In patients aged over 55 years of age, and in all Afro-Caribbean patients, first-line treatment should involve either a thiazide diuretic or a calcium channel blocker. If BP is not controlled an ACE inhibitor (or ARB) should be added to the treatment regimen. If hypertension remains uncontrolled, triple therapy should be used as a third-line treatment strategy, as described earlier.
For persistently raised BP despite triple therapy, additional beta or alpha blockade may be considered. Beta-blockers should not be considered as first-line medication for newly diagnosed patients as they may be less effective in reducing major cardiovascular events than other antihypertensives.1
However, in patients who have been taking BP medication for some time and are well controlled on beta-blockers it is recommended to continue beta-blockers unless there is another reason to change medication. If BP is not being adequately controlled then a gradual reduction in beta-blocker use should be made with initiation of a different medication following the guidance above.
4. ACE inhibitors and ARBs
A Cochrane review concluded that ACE inhibitors and ARBs moderately reduce systolic and diastolic BP, and half the maximum recommended dose provided an average 90 per cent reduction in BP.2
This suggests that combination therapy is more appropriate than titrating ACE inhibitors/ARBs beyond half the maximum dose and risking dose-dependent side-effects.
The review also found that ACE inhibitors and the more expensive ARBs reduced BP to a similar extent. This supports NICE guidance, which states that ARBs should only be used in patients experiencing unacceptable side-effects with ACE inhibitors.1
ACE inhibitors are often recommended first-line for hypertension in patients with diabetes as they are thought to have a positive effect on glucose metabolism. The DREAM study supports this,3 but while helping those with impaired glucose tolerance return to normoglycaemia, ACE inhibition was not shown to offer protection against developing diabetes.
Similarly, although ACE inhibitors have been shown to reduce mortality in patients with established heart failure, there is not sufficient evidence to show that initiating ACE inhibitors protects those at high cardiovascular risk from developing failure post-MI.4
5. Calcium channel blockers
In 2000, a study showed equal outcome in terms of BP reduction with calcium channel blockade or thiazide therapy.5 A later meta-analysis reported similar findings and concluded similar benefits from calcium channel blockade, thiazide diuretics or ACE inhibitors in the treatment of hypertension in non-diabetic individuals.6
However, this study found that calcium channel blockers were probably less safe than ACE inhibitors when treating high BP in diabetics,6 suggesting another reason for using ACE inhibitors in patients with known diabetes.
From the evidence it would appear that in patients without diabetes initial choice of antihypertensive is of less importance than considering combination therapy in persistent hypertension rather than titrating up individual medications.
6. Ongoing care and referral
Treatment in most cases is life-long and patients should be counselled about this. In all established hypertensives, annual review of BP with a general health and medication review is required.
While patients with hypertension are normally managed in primary care, referral may be required (see box below).
- Dr Cumisky is a locum GP in Bath, Somerset.
|WHEN TO REFER|
1. NICE. Hypertension: management of hypertension in adults in primary care. CG34. London, 2006.
2. Heran BS, Wong MM, Heran IK, et al. Blood pressure lowering efficacy of angiotensin converting enzyme (ACE) inhibitors for primary hypertension. Cochrane Database Syst Rev 2008; (4): CD003823.
3. DREAM Trial Investigators, Bosch J, Yusuf S, et al. Effect of ramipril on the incidence of diabetes. N Engl J Med 2006; 355: 1551-62.
4. Demers C, Mody A, Teo KK, et al. ACE inhibitors in heart failure: what more do we need to know? Am J Cardiovasc Drugs 2005; 5: 351-9.
5. Brown MJ, Palmer CR, Castaigne A, et al. Morbidity and mortality in patients randomised to double-blind treatment with a long-acting calcium-channel blocker or diuretic in the International Nifedipine GITS study: Intervention as a Goal in Hypertension Treatment (INSIGHT). Lancet 2000; 356: 366-72.
6. Opie LH, Schall R. Evidence-based evaluation of calcium channel blockers for hypertension: equality of mortality and cardiovascular risk relative to conventional therapy. J Am Coll Cardiol 2002; 39: 315-22.