Hypertension

Hypertension is a major risk factor for cardiovascular disease (CVD - cerebrovascular events and ischaemic heart disease) and is therefore one of the most important preventable causes of premature morbidity and mortality in developed and developing countries. Recent Quality and outcomes framework (QOF) data suggest a prevalence of 11.3% in the UK population.
It is often symptomless, so screening is vital - before damage is done. Many surveys continue to show hypertension remains underdiagnosed, undertreated and poorly controlled in the UK.¹

Blood pressure (BP) has a skewed normal distribution within the population and the currently accepted model assumes risk is continuously related to blood pressure.^2,3,4

Hypertension

Isolated systolic hypertension

When defining hypertension, we choose to select a value above which risk is significantly increased e.g. a total CVD risk 20% over 10 years,⁷ and the benefit of treatment is clear-cut. A figure of 160/100 mmHg is usually quoted.

Although there are geographical differences in blood pressure (the absolute risk at the same level of blood pressure varies substantially), the relative increase in long-term mortality due to CVD for a given increase in blood pressure is similar.⁴
However, hypertension is only one of several cardiovascular risk factors and assessment of overall risk is vital, as it will affect the level of blood pressure one selects to treat; a cut-off of 140/90 mmHg should be used for those with an absolute risk of 1.5% per annum: see Management of Hypertension.

• Malignant hypertension: This is a syndrome characterised by severe hypertension (e.g. systolic >200, diastolic>130 mmHg) accompanied by encephalopathy or nephropathy, or by papilloedema and/or angiopathic haemolytic anaemia. Accelerated hypertension has been used to describe acutely elevated blood pressure with haemorrhages or exudates on fundoscopy. Both need urgent treatment.
• Systolic or diastolic pressure: For many years diastolic pressure was considered to be more important than systolic pressure. However, evidence from the Framingham study⁸ and MrFIT study⁹ indicates that systolic pressure is the most important determinant of cardiovascular risk.
• Hypertension in the elderly: Although age-related rise in systolic pressure can be considered part of the 'normal' ageing process, isolated systolic hypertension (ISH) in the elderly should not be ignored; the benefits of treatment are far greater than treating moderate hypertension in middle-aged patients.^10,11

All adults should have their BP measured, at least every 5 years up to the age 80. Those with high normal values (130-139/85-89 mmHg) should be checked annually.

• Use a correctly calibrated and maintained machine (manual or automatic).
• Seated BP is adequate except in elderly or diabetic patients who may have orthostatic hypotension (standing BP needed as well - after at least two minutes standing).⁵
• Remove tight clothing and support the arm with hand relaxed and cuff (of appropriate size) at heart level.
• Initially measure BP in both arms and subsequently use the arm with higher values for all measurements - in some patients the difference may be >10 mmHg.

Although outcome trials have been based on clinic or surgery BP measurement, ABPM may provide more information in equivocal treatment decisions.
There is also an increasing body of evidence that they may be a better predictor of CVD.¹²It is particularly indicated if:

• BP shows unusual variability
• BP is resistant to multiple-therapy
• There is a possibility of either hypotension or "white coat" hypertension.
• It is helpful in the diagnosis and assessment of both hypertension in pregnancy and nocturnal hypertension (or in evaluating the efficacy of BP treatment over 24 hours).

Use validated machines (wrist monitors not recommended).⁴
Measurements need adjusting upwards to compare with clinic readings by approximately 10/5 mmHg and optimum ABPM targets should be <130/80 (<130/75 in diabetics), although there is little evidence for true equivalence.⁵ Patients can take their own BPs satisfactorily,¹³ but may be subject to recording bias as much as GPs.

Essential hypertension (primary, cause unknown) accounts for the majority of cases.
Secondary hypertension is commonly caused by renal disease or pregnancy.

Renal disease

~75% are from intrinsic renal disease: glomerulonephritis, polyarteritis nodosa, systemic sclerosis, chronic pyelonephritis, or polycystic kidneys.
~25% are due to renovascular disease most frequently atheromatous (elderly cigarette smokers, e.g. with peripheral vascular disease) or fibromuscular dysplasia (more common in younger females).

Endocrine disease

• Cushing's Syndrome
• Conn's syndrome
• Phaeochromocytoma
• Acromegaly
• Hyperparathyroidism

Others

Coarctation, pre-eclampsia/pregnancy, drugs

Usually asymptomatic, except malignant hypertension.

All patients need a full history and physical examination.
Look hard for a cause in the young, severe hypertensive; be more restrained in the older patient, as diagnostic yield and treatment benefits are less.
Start by talking to the patient:

• Take a full drug history (NSAIDs, oral contraceptives, steroids, liquorice, sympathomimetics ie. cold cures).
• Is he or she aware of the hypertension? Episodic feelings 'as if about to die' or headaches, or paroxysmal sweats or palpitations, suggests phaeochromocytoma
• Consider renal causes: Is there a present, past or family history of renal disease? Are the kidneys palpable? Is there an abdominal or loin bruit (renovascular disease) or delayed or weak femoral pulses (coarctation).
• Does the patient look cushingoid or might he have Conn's syndrome (tetany, weak muscles, polyuria, hypokalaemia)?
• Consider contributory factors: obesity, excess alcohol, salt intake and lack of exercise, environmental stress, and cardiovascular risk factors (smoking, diabetes, cholesterol and family history) ready for your management plan (use Primary CVD Risk Calculator if appropriate).⁷

Assess degree of end organ damage or complications of hypertension; previous stroke, TIA, dementia or known LVH/LV strain, IHD, peripheral vascular disease, renal impairment? Perform ophthalmoscopy; dilate with 1% tropicamide if poor view.

Investigations

Routine investigation should be limited to:

• Urine dipstick test for protein and blood
• Serum creatinine and electrolytes
• Fasting blood glucose
• Fasting serum total and HDL cholesterol
• ECG
• Echocardiography - useful in young patients who commonly have ECGs with voltage criteria of LVH, without T wave abnormalities
• Specific (if a secondary cause suspected):
  • Plasma calcium
  • CXR
  • Renal ultrasound
  • IVU
  • Renal arteriography
  • 24 hour urinary VMA x 3
  • Urinary free cortisol

Referral to a specialist may be appropriate for some of these tests.

• Urgent treatment needed: malignant hypertension, severe hypertension (>220/>120 mmHg) or impending complications (e.g. transient ischaemic attack, left ventricular failure).
• Possible underlying cause: low K , Na elevated (possible Conn's); elevated creatinine, proteinuria or haematuria; sudden onset or rapidly worsening or resistant hypertension (i.e. needs >3 drugs); Young Age: patient aged <20, or <30 years needing treatment.
• Therapeutic problems: multiple drug intolerance or contraindications, persistent non-compliance or treatment refusal (the reluctant hypertensive).
• Special situations: hypertension in pregnancy,¹⁴ unusual BP variability, "white coat hypertension".

For a full discussion on CVD risk assessment, treatment thresholds and their modification dependent on target organ damage and concurrent diseases see related article Management of Hypertension.