Disorders of Blood Pressure

DISORDERS OF BLOOD PRESSURE

Abnormal regulation of blood pressure can lead to serious health problems. Among these, hypertension is the most common and clinically significant disorder.

HYPERTENSION

Hypertension is defined as a persistent and consistent elevation of blood pressure, in which systolic and/or diastolic pressures remain above normal limits for a prolonged period.

Hypertension is broadly classified into:

1.     Essential hypertension

2.     Secondary hypertension

Essential Hypertension

Essential hypertension is also known as primary or idiopathic hypertension, as no single identifiable cause can be determined. It accounts for the majority of hypertension cases.

Essential hypertension is further divided into:
a. Benign (chronic) hypertension
b. Malignant (accelerated) hypertension

Benign (Chronic) Hypertension

In benign hypertension, the rise in blood pressure is usually mild to moderate and develops slowly over many years.

In many individuals, the condition remains asymptomatic for a long time. Often, complications such as:

• Heart failure
• Cerebrovascular accident (stroke)
• Myocardial infarction

may be the first clinical signs of hypertension.

Risk factors for benign hypertension include:

• Obesity
• Diabetes mellitus
• Family history
• Cigarette smoking
• Sedentary lifestyle
• High intake of salt or alcohol
• Psychological stress

Stress is known to increase sympathetic activity and may contribute to raised blood pressure.

Malignant (Accelerated) Hypertension

Malignant hypertension is a rapid and severe form of hypertension with a sudden rise in blood pressure.

• Diastolic pressure often exceeds 120 mm Hg
• The condition progresses quickly
• Effects are serious and immediately apparent

Common complications include:

• Retinal haemorrhages
• Papilloedema (swelling around the optic disc)
• Encephalopathy (cerebral oedema)
• Progressive renal disease
• Cardiac failure

Malignant hypertension is a medical emergency requiring urgent treatment.

Secondary Hypertension

Secondary hypertension develops as a result of other underlying diseases and accounts for about 5% of all hypertension cases.

Kidney Disease

Raised blood pressure is a common complication of many kidney disorders.

In kidney disease:

• Salt and water retention occurs
• Excessive renin activity may be present
• Blood volume increases, leading to hypertension

Endocrine Disorders

a)    Adrenal Cortex

Excess secretion of hormones such as aldosterone and cortisol causes:

• Increased sodium and water retention
• Increased blood volume
• Elevated blood pressure

Conditions include:

• Conn’s syndrome (aldosterone-secreting tumour)
• Excess cortisol secretion due to pituitary stimulation or adrenal tumours

b)    Adrenal Medulla

Excess secretion of:

• Adrenaline (epinephrine)
• Noradrenaline (norepinephrine)

leads to marked elevation of blood pressure, as seen in phaeochromocytoma.

Structure of the Aorta

Hypertension may develop in branching arteries proximal to a narrowing or stricture, such as in congenital coarctation of the aorta.

Drug Treatment

Some drugs may cause hypertension as a side effect, including:

• Corticosteroids
• Oral contraceptives

Effects and Complications of Hypertension

Long-standing and progressively rising blood pressure produces serious effects on blood vessels and organs.

The higher the blood pressure and the longer it remains uncontrolled, the greater the damage.

Hypertension promotes atherosclerosis and affects specific organs.

i) Heart

To overcome sustained high arterial pressure:

• The heart increases the rate and force of contraction
• Cardiac workload increases

This leads to:

• Cardiac hypertrophy
• Increased risk of aneurysm formation
• Ischaemic heart disease

ii) Brain

Hypertension commonly causes stroke, often due to cerebral haemorrhage.

Effects depend on:

• Size of the ruptured vessel
• Location of bleeding

Repeated rupture of small vessels (microaneurysms) causes progressive neurological disability.

iii) Kidneys

Essential hypertension causes kidney damage.

• Early damage may be reversible
• Prolonged hypertension leads to progressive loss of kidney function
• Activation of the renin–angiotensin–aldosterone system worsens hypertension
• Ultimately leads to renal failure

iv) Blood Vessels

High blood pressure damages blood vessels by:

• Hardening small arteries
• Accelerating atheroma formation in large arteries

Damage is more severe in individuals with:

• Diabetes mellitus
• Smoking habits