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Describe hypertension with its types and the pathology of hypertensive heart disease.

Pathology · 2nd Professional — Para-Clinical

Definition and Classification

Hypertension is a sustained elevation of arterial blood pressure; the usual threshold for diagnosis is 140/90 mmHg, though lower cut-offs are now used in some guidelines.

Type	Share	Cause
Primary (essential, idiopathic)	90–95%	Multifactorial — genetic, sodium intake, obesity, stress, renin–angiotensin and sympathetic activity
Secondary	5–10%	Renal (the commonest — renal artery stenosis, glomerulonephritis, polycystic kidney); endocrine (Conn, Cushing, phaeochromocytoma, thyroid, acromegaly); coarctation of the aorta; drugs (oral contraceptives, steroids, NSAIDs); pregnancy

Course	Features
Benign hypertension	Gradual, asymptomatic for years; the great majority
Malignant (accelerated) hypertension	Diastolic usually above 120 mmHg with papilloedema, renal failure and encephalopathy; rapidly fatal within 1 to 2 years if untreated

Vascular Pathology

Lesion	Appearance	Setting
Hyaline arteriolosclerosis	Homogeneous pink hyaline thickening of the arteriolar wall with luminal narrowing; leakage of plasma proteins	Benign hypertension and diabetes; causes benign nephrosclerosis with a finely granular kidney surface
Hyperplastic arteriolosclerosis	Concentric laminated "onion-skin" thickening of smooth muscle	Malignant hypertension
Necrotising arteriolitis	Fibrinoid necrosis of the vessel wall	Malignant hypertension — gives the "flea-bitten" kidney from petechial haemorrhages
Accelerated atherosclerosis	Plaques in large arteries	Both forms

Hypertensive Heart Disease

Pressure overload causes concentric left ventricular hypertrophy — the wall thickens while the cavity stays normal or small
Criteria — left ventricular wall over 1.5 cm and heart weight above about 500 g, in the absence of another cause
Microscopy — myocyte hypertrophy with enlarged, rectangular "box-car" nuclei, and interstitial fibrosis
Consequences — diastolic dysfunction first, then left atrial enlargement and atrial fibrillation, then systolic failure with dilatation; also ischaemia (the thick muscle outgrows its supply), arrhythmia and sudden death
Cor pulmonale is the right-sided equivalent, from pulmonary hypertension due to lung disease

CLINICAL PEARL

Hypertrophy is at first an adaptation and then becomes the disease. Thickening the wall normalises wall stress by Laplace’s law, so the ventricle copes. But the hypertrophied muscle has a relatively reduced capillary density and a higher oxygen demand, so it becomes ischaemic and fibrotic — and the compensation that saved it is what eventually kills it.

Effects on Other Organs

Organ	Effect
Brain	Intracerebral haemorrhage from charcot–bouchard microaneurysms, classically in the basal ganglia; lacunar infarcts; hypertensive encephalopathy
Kidney	Benign nephrosclerosis with a finely granular surface; malignant nephrosclerosis with a flea-bitten surface; chronic renal failure
Eye	Hypertensive retinopathy — arteriolar narrowing, arteriovenous nipping, flame haemorrhages, cotton-wool spots, and papilloedema in malignant hypertension
Large vessels	Accelerated atherosclerosis; aortic dissection and aneurysm

Applied Aspects

Hypertension is the leading modifiable risk factor for stroke, and its control is the single most effective stroke prevention available
It is asymptomatic until it causes damage — hence "the silent killer", and hence the case for population screening
Suspect a secondary cause in the young, in resistant hypertension, in sudden onset or worsening, with hypokalaemia, or with an abdominal bruit
Malignant hypertension is an emergency, but the pressure must be reduced gradually — too rapid a fall causes cerebral and renal hypoperfusion
Hypertension is increasingly common in India, including in rural areas, and remains substantially undiagnosed and undertreated

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