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Chapter 77: Hypertension

INTRODUCTION

The greatest danger to a man is that someone will discover hypertension and some fool will try to reduce it.

JOHN HAY 1931

Hypertension is a serious community disorder and the most common condition requiring long-term drug therapy in Australia. It is a silent killer because most people with hypertension are asymptomatic and unaware of their problem. Epidemiological studies have demonstrated the association between hypertension and stroke, coronary heart disease, kidney disease, heart failure and atrial fibrillation. Treatment may be lifelong, hence the need for careful work-up.

  • Target organs that can be damaged by hypertension include the heart (failure, LVH, ischaemic disease), kidney (kidney insufficiency), retina (retinopathy), blood vessels (peripheral vascular disease, aortic dissection) and brain (cerebrovascular disease).

  • Almost 6% of the Australian disease burden is due to hypertension.1

  • Factors increasing the chances of dying in hypertensive patients are: male, onset at a young age, family history, increased diastolic pressure.2

DEFINITIONS AND CLASSIFICATION

  • The various categories of BP are arbitrarily defined (and change over time in different guidelines) according to BP values for both diastolic and systolic readings (see TABLE 77.1).3,4

  • Isolated systolic hypertension is that of ≥140 mmHg in the presence of a diastolic pressure <90 mmHg.

  • Hypertension is either essential or secondary (see TABLE 77.2).

  • Essential hypertension is the presence of sustained hypertension in the absence of underlying, potentially correctable kidney, adrenal or other factors.

  • Malignant hypertension is that with a diastolic pressure >120 mmHg and exudative vasculopathy in the retinal and kidney circulations.

  • Refractory hypertension is a BP >140/90 mmHg despite maximum dosage of 2 drugs for 3–4 months.

Table 77.1Definition and classification of blood pressure in adults aged 18 years and older measured as sitting blood pressure (mmHg)4,5
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Table 77.1 Definition and classification of blood pressure in adults aged 18 years and older measured as sitting blood pressure (mmHg)4,5

Category

Systolic

Diastolic

Optimal

<120

<80

Normal

120–129

80–84

High normal

130–139

85–89

Grade 1 hypertension (mild)

140–159

90–99

Grade 2 hypertension (moderate)

160–179

100–109

Grade 3 hypertension (severe)

≥180

≥110

Isolated systolic hypertension

≥140

<90

Note: When a patient’s systolic and diastolic BPs fall into different categories, the higher category should apply.

Table 77.2Causes of hypertension
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Table 77.2 Causes of hypertension

Essential (90–95%)

Secondary (approx. 5–10%)

  Kidney <3%

  • glomerulonephritis

  • reflux nephropathy

  • kidney artery stenosis (see later in this chapter)

  • other renovascular disease

  Endocrine: 0.3–1%

  • primary aldosteronism (Conn syndrome) (see CHAPTER 14)

  • Cushing syndrome (see CHAPTER 14)

  • phaeochromocytoma (see CHAPTER 14)

  • oral contraceptives

  • other endocrine factors

  Coarctation of the aorta

  Immune disorder (e.g. polyarteritis nodosa)

  Drugs (e.g. NSAIDs, corticosteroids)

  Pregnancy

For adults aged 18 years and older, hypertension is repeated measurements of:

  • diastolic ...

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