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Chapter 86: 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).

  • Deaths in hypertensive patients have been shown to be due to stroke 45%, heart failure 35%, kidney failure 3% and others 17%.1

  • Almost half of the Australian cardiovascular disease burden is due to hypertension.2

  • 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 according to BP values for both diastolic and systolic readings (see TABLE 86.1).4,5

  • 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 86.2).

  • 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 two drugs for 3–4 months.

Table 86.1Definition and classification of blood pressure adults aged 18 years and older measured as sitting blood pressure (mmHg)4,5
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Table 86.1 Definition and classification of blood pressure 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

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

Table 86.2Causes of hypertension
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Table 86.2 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 23)

  • Cushing syndrome (see CHAPTER 23)

  • phaeochromocytoma (see CHAPTER 23)

  • oral contraceptives

  • other endocrine factors

Coarctation of the aorta

Immune disorder (e.g. polyarteritis nodosa)

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