The Basics - Hypertension

Hypertension must be managed to reduce the risk of cardiovascular disease, writes Dr Raj Thakkar.

One in five people have raised BP, the disease becoming more prevalent with age. About 28 per cent of the UK population between 40 and 79 are affected. Almost 50 per cent of over 80s are hypertensive.

Definitions of hypertension vary but in general terms it is considered to be the level at which the patient is at significant risk of cardiovascular disease (CVD).

Secondary causes of hypertension include renal disease

NICE defines hypertension as a persistently raised BP above 140/90mmHg. Target BP in type-2 diabetes is 140/80mmHg, or 130/80mmHg if there is evidence of retinopathy, nephro-pathy or CVD.1

Cardiovascular risk
In patients below the age of 50, according to Framingham data, diastolic hypertension is the best predictor of CVD, whereas between the ages of 50 and 60 both the systolic and diastolic pressures are important.2

After 60, the diastolic pressure tends to fall and patients often present with isolated systolic hypertension (ISH).

Essential hypertension accounts for approximately 95 per cent of cases. Secondary causes, which are often considered in resistant disease or in young patients, may be due to a number of conditions or factors including drugs, obesity, endocrine disease, renal disease, coarctation of the aorta, Paget's disease of the bone and myeloproliferative diseases.

Diagnosis
BP measurements should be taken on at least two occasions, a month apart. NICE does not recommend the routine use of ambulatory or home monitors in primary care, although they may be useful to confirm white-coat hypertension.

If a reading of greater than 140/90mmHg is found in clinic, another confirmatory reading should be taken at the end of the consultation.

On diagnosis, the patient should be educated on what hypertension is and why its treatment is so important.

Modifiable risk factors such as smoking, alcohol intake and diet should be managed. Salt restriction can significantly reduce BP.3

Exercise and weight loss may account for a 7/5mmHg reduction in BP while reducing alcohol consumption may reduce BP by up to 8/3mmHg.

A 10-year cardiovascular risk assessment should be made in patients who do not have a formal diagnosis of CVD.

Important features in the history and examination include whether the patient is diabetic or has renal or cardiac disease.

In addition, consider what drugs they take, e.g. steroids, and whether the patient has any signs or symptoms of CVD.

Is there radio-femoral delay or a murmur suggestive of coarctation of the aorta? Does the patient look Cushingoid? Are there any renal bruits or other signs of renal disease such as a renal mass or evidence of transplant?

Investigations
Bloods should be checked including U&Es, fasting lipids and glucose. Urine should be tested for proteinuria and haematuria and an ECG should carried out to look for other evidence of CHD.

According to a recent study, however, an ECG is not sensitive enough to exclude LVH in the context of hypertension.4

In secondary hypertension, when coarctation of the aorta is suspected, an echocardiogram should be ordered.

Any cause of renal disease, including diabetes, may predispose patients to hypertension. Where renal hypertension is suspected, renal function should be rechecked.

Other tests that may be considered include MSU for microscopy and culture, inflammatory and autoimmune screen including ANCA and ANA, and renal ultrasound.

Where renal artery stenosis is suspected, often seen when an unexpected fall in renal function is seen with ACE inhibitors, renal angiography may be required. A normal potassium concentration does not exclude hyperaldosteronism.

If concerned, it is better to measure the aldosterone to renin ratio which, when it exceeds 800, suggests primary hyperaldosteronism.

Patients with headaches, sweats, palpitations, tremor and hypertension may have an underlying phaeochromocytoma. If suspicious, the next appropriate test is a 24-hour collection for urinary catecholamines.

Cushing's syndrome may present with hypertension, centripetal obesity, diabetes, proximal myopathy and hirsutism.

Management
Generally, cases of secondary hypertension should be referred.

Treatment of essential hypertension should aim to reduce BP to 140/90mmHg or lower.1 Drug therapy should be offered to patients with a BP of ≥160/100mmHg.

Those who have a 10-year risk of CVD ≥20 per cent, existing CVD or target organ damage should be treated by drugs if their BP is ≥140/90mmHg.

Patients over the age of 55 and African-Caribbeans tend to be more renin resistant and, as such, calcium-channel blockers or thiazide diuretics should be used first line in this group of patients.1

Younger Caucasian patients should be offered ACE inhibitors, assuming they do not have significant aortic stenosis or renal artery stenosis. Renal function and electrolytes should be monitored when initiating or increasing the dosage of ACE inhibitors or angiotensin receptor blockers (ARBs).

Beta-blockers are fourth line in the treatment of hypertension according to the NICE guidelines.1 They still have their place, particularly when treating co-existing conditions such as post-MI and palpitations.

Other drugs that may be used include alpha-blockers, which may be particularly helpful in men with prostatism, and the aldosterone antagonist, spironolactone, which also reduces mortality in cardiac failure.5 Care should be taken to monitor potassium in those taking spironolactone, particularly in patients also taking ACE inhibitors or ARBs.

Follow up
Patients should be followed up frequently at the outset of diagnosis to motivate lifestyle changes, monitor BP and assess drug side-effects. Once their BP is well controlled, they may be followed up six-monthly.

Patients with complex medical histories may be reviewed more frequently.

  • Dr Thakkar is a GP in Wooburn Green, Buckinghamshire

References

1. NICE clinical guideline 34: Hypertension: management of hypertension in adults in primary care.

2. Framingham Heart Study.

3. Stamler J. The INTERSALT Study: background, methods, findings, and implications. Am J Clin Nutr 1997; 65(2): 626S-42S.

4. Pewsner D, Juni P, Egger M et al. Accuracy of electrocardio-graphy in diagnosis of left ventricular hypertrophy in arterial hypertension. BMJ 2007; 335: 711.

5. Pitt B, Zannad F, Remme W J et al. The effect of spironolactone on morbidity and mortality in patients with severe heart failure. N Engl J Med 1999; 341(10): 709-17.

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins

Register

Already registered?

Sign in

Before commenting please read our rules for commenting on articles.

If you see a comment you find offensive, you can flag it as inappropriate. In the top right-hand corner of an individual comment, you will see 'flag as inappropriate'. Clicking this prompts us to review the comment. For further information see our rules for commenting on articles.

comments powered by Disqus