Hypertension

Definition/diagnostic criteria Hypertension is a condition defined by the presence of a persistently elevated systolic and/or diastolic pressure within the arterial system. Current NICE guidance for hypertension was updated in 2019 and reinforced the importance of ambulatory or home BP monitoring (ABPM or HBPM) to confirm a diagnosis, with a threshold diagnostic level of ≥135/80mmHg on average readings.¹

Epidemiology^2,3 Hypertension is an independent, modifiable CV risk factor. It is associated with an increased risk of atherosclerotic CVD, such as MI and stroke, as well as heart failure and CKD. It is a major preventable cause of premature mortality, morbidity and disability, and addressing it was identified by Public Health England (now the UK Health and Security Agency) as one of the key opportunities to save lives and reduce health inequality over the coming years.

In a 2021 survey in England, 30% of the adult population had a diagnosis of hypertension (either controlled or uncontrolled) and 15% of the population had a diagnosis without being on treatment. Prevalence was similar between the sexes and the majority (60%) of diagnoses was in adults ≥65 years of age. The age-standardised prevalence of hypertension is significantly increased in areas of social deprivation.

According to WHO, 46% of adults with hypertension worldwide are undiagnosed and only 21% have it under control.

Key risk factors for developing hypertension include increasing age, genetics, being overweight or obese, reduced physical activity and a high-salt diet.

Diagnosis
Clinical features: Hypertension is largely asymptomatic but can be associated with target organ damage, in particular involving the cardiovascular system and kidneys. This should be routinely assessed as part of ongoing management.

Investigations: Blood pressure can fluctuate throughout the day and any patient with a clinic reading >140/90 mmHg should be evaluated on multiple readings taken at different times using either ABPM or HBPM.

When using ABPM, at least two measurements per hour should be taken during normal waking hours for the patient and an average of at least 14 measurements during this time should be used to confirm a diagnosis. For HBPM, two consecutive measurements should be taken for each recording, at least one minute apart and with the person seated. Recordings should be taken twice daily, ideally in the morning and evening and continued for at least four days, ideally seven days. First day measurements should be discarded and an average of the remaining records used for diagnosis.

A diagnosis of hypertension is confirmed when ABPM daytime or HBPM average is ≥135/85mmHg. For patients who have not reached the diagnostic criteria, BP should be re-evaluated at least five-yearly.

CVD risk assessment: All patients with confirmed hypertension should undergo a formal CVD risk assessment (e.g., using QRISK 2 or 3) and assessment for target organ damage. This should include testing the urine for estimation of the ACR and haematuria as well as testing the blood for HbA1c, eGFR, creatinine, electrolytes and lipid profile. A 12-lead ECG should also be performed to identify signs of underlying left ventricular hypertrophy and fundoscopy performed to identify retinopathy.

Specialist investigations should be considered if there is a suggestion of a secondary cause of hypertension, e.g., hypertension in young patients, particularly if not obese and there is no family history of hypertension. Immediate referral is required for suspected phaeochromocytoma (e.g., headache with palpitations or abdominal pain) or accelerated hypertension (BP >180/100mmHg with associated clinical symptoms or signs, e.g., breathlessness or oedema).

Treatment Lifestyle interventions are the foundation of all BP lowering strategies and class 1 recommendations from the European Society of Cardiology (ESC)⁴ include:

• Salt and alcohol restriction.
• Increased consumption of vegetables and reduced consumption of red meat.
• Aiming for a normal BMI and waist circumference.
• Undertaking regular aerobic exercise.
• Cessation of smoking.

The BP-lowering effect of sodium restriction is likely to be greater in black people, older patients and patients with diabetes, metabolic syndrome or CKD.

If there is associated type 2 diabetes, established CVD, evidence of end organ damage or ≥10% 10-year CVD risk, drug treatment should be considered if average BP (from daytime ABPM or HBPM readings) remains ≥135/85mmHg, according to current NICE guidelines.¹

Patients with a clinic BP of ≥160/100mmHg but <180/120mmHg and subsequent ABPM daytime average or HBPM average of ≥150/95mmHg should also be offered pharmacological treatment in addition to lifestyle measures.

The aim of treatment is to reduce BP to and maintain BP at <135/85mmHg for adults aged  under 80 years and <145/85mmHg for adults aged 80 years or older, taking into account frailty. Most patients will require combination drug therapy to achieve satisfactory BP control. The risks of overtreatment in elderly and frail patients in particular should always be considered, including an increased risk of falls and increased risk of acute kidney injury.

Pharmacological treatment:

• First-line treatment is either ACE inhibitor or ARB therapy for patients with type 2 diabetes regardless of age or ethnicity, or if under 55 years of age and not of African-Caribbean or black African ethnicity.
• If patient is aged 55 or older or of African-Caribbean or black African ethnicity, then a calcium channel blocker is the recommended first-line option, replacing with a thiazide-like diuretic if not tolerated.
• Second- and third-line treatments involve combining an ACE inhibitor or ARB with a calcium channel blocker and/or a thiazide-like diuretic.

Compliance must be assessed at every stage if treatment targets are not met and prior to initiating fourth-line treatment if required. For patients without significant hyperkalaemia (K⁺ ≤4.5mmol/l), spironolactone 25mg is the recommended treatment.

An assessment of postural hypotension should be undertaken if there are any suggestive symptoms, including falls or postural dizziness. BP should be measured while a patient is lying down (or seated if inconvenient) and measured again after the patient has been standing for at least one minute. A review of the treatment regime should occur if systolic BP falls by ≥20mmHg or diastolic BP falls by ≥10mmHg.

Specialist advice should be sought for treatment resistant hypertension (ie, uncontrolled hypertension despite adherence to optimal tolerated doses of four drugs).

Prognosis The prognosis of hypertension is very much dependent on how early and how well BP control is achieved. Ideally BP control should be achieved before significant target organ damage has occurred. Hypertension should, however, be considered a progressive disease and it will have a tendency to worsen with time. Isolated systolic hypertension is a common finding in the elderly and should be given the same consideration for treatment as for combined systolic and diastolic hypertension, taking into consideration the presence of frailty.

Written by Dr Yassir Javaid, a GP specialist in cardiology at Imperial College Healthcare NHS Trust.