Hypertension

Overview

Hypertension describes high blood pressure and is a major risk factor for stroke and heart disease. Blood pressure varies from person to person, and usually lies normally in the range of 90/60mmHg to 140/90mmHg.

Definitions

NICE has recommended the following definitions for hypertension:

• Stage 1 hypertension:
  • Clinic blood pressure ≥140/90mmHg
  • Ambulatory/home blood pressure ≥135/85mmHg
• Stage 2 hypertension:
  • Clinic blood pressure:
  • Ambulatory/home blood pressure:
• Stage 3/severe hypertension:
  • Clinic blood pressure:
  • Ambulatory/home blood pressure:

The “white coat effect” is a ≥20/10mmHg difference in the clinic and ambulatory/home blood pressures. This happens in some people as they may feel stressed having their blood pressure monitored in a clinic.

There can be hypertensive crises which are medical emergencies. These are covered in a separate chapter.

Screening

As hypertension has no symptoms until its end-organ damage manifests, all adults should have their blood pressure measured at least every 5 years up to the age of 80 years, and then annually thereafter.

Epidemiology

• Prevalence rises to more than 50% in people >60 years
• Third biggest risk factor for premature death and disability after smoking and diet
• Globally, around 25% of adults have hypertension

Aetiology

Essential (primary hypertension) – 90% of cases:

• No identifiable cause

Secondary hypertension – 10% and due to underlying pathology:

• Renal disease – most common cause of secondary hypertension
  • Examples are renovascular disease e.g. renal artery stenosis due to atherosclerosis or fibromuscular dysplasia
• Endocrine disease:
  • Cushing’s syndrome
  • Hyperaldosteronism
  • Hyperthyroidism/hypothyroidism
  • Phaeochromocytoma
  • Acromegaly
  • Hyperparathyroidism
• Obstructive sleep apnoea
• Coarctation of the aorta
• Pre-eclampsia and pregnancy-induced hypertension
• Some drugs/toxins:
  • Alcohol
  • Cocaine
  • Amphetamines
  • Antidepressants e.g. venlafaxine
  • Combined oral contraceptive pill
  • Glucocorticoids

Risk Factors

• Increasing age
• Sex – more common in men if <65, but higher in women between 65-74 years
• Ethnicity – Black African/Hispanic people are at higher risk
• Family history
• Social deprivation
• Smoking
• Excess alcohol
• Excess dietary salt
• Obesity
• Low exercise
• Anxiety and emotional stress

Complications

• Coronary artery disease
• Stroke/TIA
• Left ventricular hypertrophy
• Heart failure
• Hypertensive retinopathy
• Peripheral arterial disease
• Hypertensive nephropathy
  • Hypertension can damage the kidneys and potentially lead to chronic kidney disease
• Aortic dissection
  • There is a very strong association between hypertension and aortic dissection
• Malignant hypertension
  • Undiagnosed or inadequately treated essential hypertension is a risk factor for this

Presentation

Patients are usually asymptomatic in essential hypertension. They may have symptoms of underlying causes or damage caused by hypertension itself:

• Cushingoid features e.g. abdominal striae, central obesity and distal muscle wasting
• Tetany, weak muscles, and hyperkalaemia – suggest hyperaldosteronism
• Episodic headaches, sweats, and palpitations suggest phaeochromocytoma
• Signs of thyroid disease e.g. tremors and heat intolerance in hyperthyroidism
• Headaches 
• Visual changes – decreased acuity, papilloedema, floaters
• Dyspnoea – suggests possible congestive heart failure
• Chest pain and anginal symptoms – suggest coronary artery disease
• Sensory or motor deficits – suggests stroke/TIA

Assessment

All patients should have the following:

• Blood pressure measurement on two or more occasions with the average recorded
  • Blood pressure should be measured in both arms. A difference in the arms may suggest aortic dissection

Differential Diagnoses

Renal artery stenosis

• Renal artery bruits may be present
• Renal function may decline when introducing ACE inhibitors
• Typically younger patients with hypertension that’s difficult to control

Chronic kidney disease

• Oedema may be present
• Chronic anaemia may be seen

Aortic coarctation

• Differences are found in the upper and lower extremity blood pressures
• Pulses may be absent/reduced in the lower limbs

Obstruction sleep apnoea

• Classically obese patients that are sleepy during the day and snore at night/choke during sleep

Hyperaldosteronism

• Tetany, muscle aches, and polyuria may be present
• Sodium usually high/normal, and potassium low

Hyperthyroidism

• Heat intolerance, weight loss, palpitations

Hyperparathyroidism

• Symptoms of hypercalcaemia: renal stones, bone pain, abdominal pain, constipation, depression

Cushing’s syndrome

• Weight gain, abdominal striae, bruising, distal muscle wasting

Phaeochromocytoma

• Episodes of hypertension, palpitations, flushing, and headaches 

Acromegaly

• Enlargement of the hands, feet, jaw, forehead bossing

Gestational hypertension

• High blood pressure found after 20 weeks gestation in a previously normotensive patient

Investigations

Initial

• Measure in the clinic: if between 140/90mmHg and 180/120mmHg then offer ambulatory/home blood pressure monitoring (ABPM/HBPM)

Investigations for end-organ damage

• ECGs:
  • May show left ventricular hypertrophy or signs of myocardial ischaemia
  • A normal result does not rule out coronary artery disease
• Urine dipstick:
  • May show signs of renal disease e.g. haematuria/proteinuria
• Urea and electrolytes (U&Es):
  • To check for renal disease which may cause or be a cause of hypertension
• Thyroid function tests(TFTs):
  • Indicated if there are signs of hypo-/hypothyroidism
• Lipid panel:
  • To check for dyslipidaemia
• HbA1c:
  • To check for diabetes mellitus

Other investigations may be needed to identify the underlying cause. These are mentioned in their corresponding chapters.

Diagnosis

Hypertension is diagnosed and staged if the two following criteria are met:

• Clinic blood pressure of ≥140/90mmHg and
• ABPM/HBPM ≥135/85mmHg

Management

All patients

• A low-salt diet
• Reduced caffeine intake
• Stop smoking
• Reduce alcohol intake
• Healthy and balanced diet
• Lose weight if necessary

Medical management is offered to patients that:

• Have stage 2 hypertension
• Under 80 years of age with stage 1 hypertension that have:
  • Type 2 diabetes
  • Chronic kidney disease
  • End-organ damage
  • QRISK score ≥10%

Antihypertensive Drugs

(A) Angiotensin-converting enzyme inhibitors (ACEi):

• Examples: ramipril, lisinopril, enalapril
• Mode of action: inhibits the conversion of angiotensin I to angiotensin II
• Common side effects:
  • Dry cough
  • Postural hypotension
  • Acute kidney injury, especially in renal artery stenosis
  • Angioedema
  • Hyperkalaemia
• Cautions:
  • Avoid in pregnancy
  • Renal function must be checked 2 weeks after starting as renal function may decline in people with renovascular disease

(A) Angiotensin II receptor blockers (ARB):

• Examples: candesartan, valsartan
• Mode of action: blocks the angiotensin II receptor and prevents its action
• Common side effects:
  • Hyperkalaemia
• Cautions:
  • Avoid in pregnancy
  • Do not combine with ACEi

(C) Calcium channel blockers (CCBs):

• Examples: amlodipine, felodipine, nifedipine
• Mode of action: block voltage-gated calcium channels and relax vascular smooth muscle and decrease the force of heart contractions
• Common side effects:
  • Ankle swelling
  • Headache
  • Dizziness
  • Bradycardia
  • Flushing

(D) Thiazide-like diuretics:

• Examples: indapamide, chlortalidone
• Mode of action: inhibit sodium absorption at the start of the distal convoluted tubule
• Common side effects:
  • Hyponatraemia
  • Hypokalaemia
  • Hypercalcaemia
  • Hyperuricaemia
  • Dehydration
• Cautions:
  • Can worsen diabetes, gout, and systemic lupus erythematosus
  • Can cause erectile dysfunction in men

Alpha-blockers:

• Examples: doxazocin and terazosin
• Mode of action: inhibit post-synaptic alpha1-adrenergic receptors leading to vasodilation of the blood vessels
• Common side effects:
  • Dizziness
  • Drowsiness
  • Orthostatic hypotension

Beta-blockers:

• Examples: carvedilol, metoprolol, bisoprolol
• Mode of action: block beta-adrenergic receptors and lead to vasodilation and reduced heart contraction strength
• Common side effects:
  • Diabetes
  • Impotence
  • Bradycardia
  • Fatigue
  • Cold hands and feet
  • Worsening psoriasis
• Cautions:
  • Contraindicated in asthma
  • Contraindicated in 3^rd-degree heart blocks

Aldosterone antagonists:

• Examples: spironolactone, eplerenone
• Mode of action: bind to aldosterone receptors and reduces sodium absorption and promotes water excretion
• Common side effects:
  • Hyperkalaemia
  • Spironolactone – gynaecomastia
• Cautions:
  • Contraindicated in hyperkalaemia or Addison’s disease

Stepwise management of hypertension

Treatment Targets

Monitoring

• When adjusting medication doses, blood pressure should be monitored every 2-4 weeks
• When stable, the blood pressure should be reviewed every 6-12 months
• Check U&Es annually

Patient Advice

• Patients should:
  • Stop smoking
  • Limit alcohol intake
  • Limit salt intake
  • Exercise regularly
• Patients should also be educated on the consequences of hypertension and the importance of its management

Prognosis

• Hypertension can increase the risk of:
  • Heart failure
  • Coronary artery disease
  • Chronic kidney disease
  • Peripheral arterial disease
  • Vascular dementia
• Correction of high blood pressure reduces these risks significantly.