Epidemiology

Hypertension is often symptomless, so screening is vital - before damage is done. Many surveys continue to show that hypertension remains underdiagnosed, undertreated and poorly controlled in the UK.^[1] Overall, the prevalence of hypertension (at least ≥140/90 mm Hg or on treatment for hypertension) in those aged over 35 was 32% in men and 27% in women.^[2]

The prevalence significantly increased with age in both sexes:

• About 33% of men and 25% of women aged 45-54 years have hypertension.
• About 73% of men and 64% of women aged ≥75 years or older have hypertension.

Screening for hypertension

All adults should have their blood pressure (BP) measured, at least every five years up to the age of 80,^[3] and at least annually thereafter.

If BP in the GP surgery is ≥140/90 mm Hg then offer ambulatory blood pressure monitoring (ABPM) to confirm the suspected hypertension, or home blood pressure monitoring (HBPM) if ABPM is not available or not tolerated.^[3]

• If using ABPM - take ≥2 readings every waking hour, and average at least 14 measurements when deciding whether hypertension is present.
• If using HBPM - on each occasion take two consecutive BP measurements (<1 minute apart), with the person seated. Take readings twice daily (morning and evening) over ≥4 days (ideally 7 days) - disregard the first day and then average the rest.

Those with high normal values (130-139/85-89 mm Hg) subsequently should be checked annually.

While waiting for further BP readings to confirm diagnosis of hypertension, look for target organ damage and assess cardiovascular risk assessment with a suitable assessment tool - look for hypertensive retinopathy, left ventricular hypertrophy on ECG, and perform blood tests (serum electrolytes, creatinine, eGFR, fasting glucose and lipids) and urinalysis for albuminuria, proteinuria or haematuria ± albumin:creatinine ratio.

Defining hypertension^[3]

Blood pressure (BP) has a skewed normal distribution within the population and the currently accepted model assumes risk is continuously related to BP. The National Institute for Health and Clinical Excellence (NICE) recommends the following definitions:

• Stage 1 hypertension - BP in surgery is ≥140/90 mm Hg and ABPM or HBPM is ≥135/85 mm Hg.
• Stage 2 hypertension - BP in surgery is ≥160/100 mm Hg and ABPM or HBPM is ≥150/95 mm Hg.
• Severe hypertension - BP in surgery is ≥180/110 mm Hg or higher.

Other considerations

• Malignant (accelerated) hypertension: this is a syndrome characterised by severe hypertension (eg systolic >200 mm Hg, diastolic >130 mm Hg) accompanied by encephalopathy or nephropathy, or by papilloedema and/or angiopathic haemolytic anaemia. Accelerated hypertension needs urgent (same day) assessment and treatment.^[3]
• Suspected phaeochromocytoma Consider this diagnosis if there is labile or postural hypotension, headache, palpitations, pallor and profuse sweating - refer for urgent (same day) assessment.^[3]
• Hypertensive crisis: a systolic blood pressure (SBP) ≥180 mm Hg or a diastolic blood pressure (DBP) ≥120 mm Hg is considered a 'hypertensive crisis'. Treatment should safely reduce BP. Immediate reduction in BP is required only in patients with acute end-organ damage.^[4][5]
• Systolic or diastolic pressure: for many years diastolic pressure was considered to be more important than systolic pressure. However, evidence from the Framingham study^[6] and the Multiple Risk Factor Intervention Trial (MRFIT) study^[7] 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.^[8][9]

Aetiology

• Essential hypertension (primary, cause unknown) accounts for the majority of cases, particularly in the older patient.
• Secondary hypertension is commonly caused by renal disease or pregnancy.
  • Renal disease - approximately 75% are from intrinsic renal disease: glomerulonephritis, polyarteritis nodosa, systemic sclerosis, chronic pyelonephritis, or polycystic kidneys.
    Approximately 25% are due to renovascular disease - most frequently atheromatous (eg elderly cigarette smokers with peripheral vascular disease) or fibromuscular dysplasia (more common in younger females).
  • Endocrine disease:
    • Cushing's syndrome
    • Conn's syndrome
    • Phaeochromocytoma
    • Acromegaly
    • Hyperparathyroidism
  • Coarctation.
  • Pre-eclampsia and hypertension in pregnancy.^[10]
  • Drugs and toxins, eg alcohol, cocaine, ciclosporin, tacrolimus, erythropoietin, adrenergic medications, decongestants containing ephedrine and herbal remedies containing licorice.

Presentation

It is usually asymptomatic, except accelerated hypertension.

All patients need a full history and physical examination. Look hard for a cause (renal, endocrine, etc. - as above) in the young, severe hypertensive.^[11][12]

Start by talking to the patient:

• Take a full drug history (non-steroidal anti-inflammatory drugs (NSAIDs), oral contraceptives, steroids, licorice, sympathomimetics, ie cold cures).
• Are they aware of the hypertension? Episodic feelings 'as if about to die' or headaches, or paroxysmal sweats or palpitations, suggest 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 or she 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.

Assess the degree of end-organ damage or complications of hypertension; previous cerebrovascular event (CVE), transient ischaemic attack (TIA), dementia or known left ventricular hypertrophy (LVH)/left ventricular (LV) strain, ischaemic heart disease (IHD), peripheral vascular disease, renal impairment? Perform ophthalmoscopy; dilate with 1% tropicamide if there is poor view.

Investigations

• Routine investigation should be limited to:
  • Urine dipstick test for protein and blood.
  • Serum creatinine and electrolytes and eGFR.
  • Fasting blood glucose.
  • Fasting serum total and high-density lipoprotein (HDL) cholesterol.
  • 12-lead ECG (looking for LVH or signs of IHD).
• Echocardiography is useful in young patients who commonly have ECGs with voltage criteria of LVH, without T-wave abnormalities.
• Specific investigations for a suspected secondary cause:
  • Plasma calcium.
  • CXR.
  • Renal ultrasound.
  • Intravenous urogram (IVU).
  • Renal arteriography.
  • 24-hour urinary vanillylmandelic acid (VMA) x 3.
  • Urinary free cortisol.

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

Indications for specialist referral^[13]

• Urgent treatment needed: accelerated hypertension, severe hypertension (>220/>120 mm Hg) or impending complications (eg transient ischaemic attack (TIA), left ventricular (LV) failure).
• Possible underlying cause: low K+, Na+ elevated (possible Conn's syndrome); elevated creatinine, proteinuria or haematuria; sudden onset or rapidly worsening or resistant hypertension (ie needs >3 drugs); young age: patient aged <20 years, or <30 years needing treatment.
• Therapeutic problems: multiple drug intolerance or contra-indications, persistent noncompliance or treatment refusal (the reluctant hypertensive).
• Special situations: hypertension in pregnancy,^[14] unusual blood pressure (BP) variability.

Management

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