Hypertension

Hypertension refers to elevated blood pressure in the arterial system. By some experts it is considered a disease, but for others it's not a disease but a risk factor for development of many diseases, most notably cardiovascular disease. It’s mostly asymptomatic. Technically arterial hypertension is more accurate, but the term "hypertension" is widely understood to mean arterial hypertension, rather than for example pulmonary hypertension.

Hypertension is a major cause of morbidity and mortality worldwide, and it’s also becoming more and more common. However, even small decreases in blood pressure in the case of hypertension cause large improvements in the risk for complications. The risk for cardiovascular death doubles for each 20/10 mmHg increase in blood pressure. Unfortunately, patients with hypertension are widely undertreated, with only 30% of people with hypertension receiving adequate treatment. Hypertension occurs in >30% of the adult population.

Primary hypertension, previously called essential hypertension due to the false belief that it was essential to maintain perfusion in elderly, is the idiopathic form of hypertension and a very prevalent condition. Hypertension is primary in 90% of cases. The remaining are secondary to an underlying disorder (see the article on secondary hypertension).

There is no "safe" upper limit of blood pressure, and so there is no precise limit as to when elevated blood pressure becomes dangerous. In fact, evidence shows increased cardiovascular risk from as low as 115/75 mmHg. However, European and American experts have made (two different) definitions for hypertension, above which treatment is felt to have more benefit than risk.

Etiology of primary hypertension

The precise cause of primary hypertension is not known, but many risk factors are known:

• Old age
• Obesity
• Increased salt intake
• Family history

Pathophysiology

Many mechanisms are probably involved in development of primary hypertension:

• Activation of renin-angiotensin-aldosterone system
• Activation of sympathetic nervous system
• Fluid and salt retention

Classification of severity

According to the European Society of Cardiology (ESC):

Severity	Systolic blood pressure (mmHg)	Diastolic blood pressure (mmHg)
Normal	<140	<90
Grade 1 HTN	140 – 160	90 – 100
Grade 2 HTN	160 – 180	100 – 110
Grade 3 HTN	>180	>110
Isolated systolic HTN	>140	<90
Isolated diastolic HTN	<140	>90

Special types

• White-coat hypertension – hypertension in a clinical scenario (hospital, clinic) but not on ambulatory measurements
• Masked hypertension – hypertension on ambulatory measurements but not in a clinical scenario
• Treatment-resistant hypertension – uncontrolled blood pressure despite the use of 3 antihypertensive agents of different classes, where one is a diuretic.
• Hypertensive crisis – an acute increase in blood pressure corresponding to grade 3 hypertension. It’s an umbrella term for two conditions, hypertensive urgency and hypertensive emergency.
  • A hypertensive urgency is a hypertensive crisis which is asymptomatic or only causes nonspecific symptoms like headache or dizziness.
  • A hypertensive emergency is a hypertensive crisis which causes end-organ damage to the heart, CNS, kidney, eye, etc.

Clinical features

Hypertension by itself is asymptomatic, but there may be findings of cardiovascular disease or renal disease. Severe hypertension may cause non-specific symptoms like headache.

Diagnosis and evaluation

The diagnosis of hypertension is not made after one measurement of elevated blood pressure. Proper diagnosis requires multiple measurements under standardised conditions at multiple consultations.

Ambulatory (24 hour) blood pressure monitoring (ABPM) involves wearing a blood pressure during a whole 24-hour period while the patient goes along with their life. It measures the blood pressure at fixed intervals of 15 – 60 minutes. ABPM can be used to confirm blood pressure readings and diagnose white coat and masked hypertension.

Home blood pressure monitoring (HBPM) requires patient training and proper equipment to be accurate.

Unless there are features to suggest secondary hypertension, newly diagnosed hypertension is managed as primary.

Treatment

The blood pressure targets for treated hypertension are:

• At least BP reduction by >20/10 mmHg, ideally to <140/90 mmHg
• Optimally:
  • If <65 years: BP target <130/80 mmHg
  • If >65 years: BP target <140/90 mmHg, but consider higher targets individually

ESC has also published more detailed blood pressure targets depending on the presence of comorbidities as well.

There are several non-pharmacological interventions which are known to decrease blood pressure, and these are the first-line treatment for hypertension:

• Achieve normal body weight (BMI 18 – 25)
• Adopt DASH diet
• Reduce dietary sodium (< 2,4 g/day, equal to 5 g/day of NaCl)
• Increase physical activity
• Decrease alcohol consumption
• Smoking cessation

However, in many people, pharmacological treatments are necessary. The 2020 International Society of Hypertension (ISH) recommends the following:

• First line: A single pill containing two antihypertensive drugs in low dose, ideally a RAAS blocker (ACEi or ARB) + calcium channel blocker
• Second line: A single pill containing two antihypertensive drugs in higher dose, ideally a RAAS blocker + calcium channel blocker
• Third line: Addition of diuretic (thiazide-like diuretic)
• Fourth line (resistant hypertension): Addition of mineralocorticoid receptor antagonist like spironolactone

The choice of antihypertensive drug should also take into account other indications the patient might have. For example, if the patient has heart failure or effort angina, a beta blocker may be a better choice as antihypertensive because it treats both the heart condition and the high blood pressure. ACEi/ARB is protective in both diabetes and heart failure. Mineralocorticoid receptor antagonists is especially protective for heart failure with preserved ejection fraction.

Antihypertensive monotherapy is usually inadequate, which is why the guidelines recommend to start combination therapy. Giving multiple antihypertensive in low or moderate doses also decrease the risk of adverse effects compared to giving one antihypertensive in full dose.

Treatment-resistant hypertension

The most common cause of treatment-resistant hypertension is poor medicine compliance of the patient. Combination drugs as well as proper education helps mitigate this.

Complications

• CNS
  • Stroke (both thromboembolic and haemorrhagic)
  • Hypertensive encephalopathy
  • Dementia
• Heart
  • Acute myocardial infarction
  • Hypertensive cardiomyopathy -> heart failure
• Kidney
  • Chronic kidney disease
• Hypertensive retinopathy
• Peripheral artery disease
• Diabetes mellitus
• Early death
• +++