Page 260 - Concise Pathology for Exam Preparation ( PDFDrive )

10 Blood Vessels 245

Q. Classify hypertension. Write briefly about the factors regulating
blood pressure and describe its morphological effects.

Ans. The clinical classification of hypertension is given in Table 10.2.

TABLE 10.2. Clinical classification of hypertension
Category Systolic (mm Hg) Diastolic (mm Hg)
Normal 90–119 60–79
Prehypertension 120–139 80–89
Hypertension
1. Stage I 140–159 90–99
2. Stage II .160 .100
Malignant hypertension .200 .140
Isolated systolic hypertension .140 , 90

• Blood pressure varies with many factors such as age, exercise, emotional disturbances
like fear and anxiety, so should be measured twice during two separate examinations
under least stressful conditions.
• Industrialized countries have a higher prevalence of hypertension.
• Hypertension is more common amongst males and Afro-Americans.
• The control of hypertension reduces mortality due to stroke and coronary artery disease.
• Systolic blood pressure correlates with stroke volume and the compliance of the aorta.
• Factors determining systolic pressure include preload (volume of blood in the left
ventricle), afterload (resistance against ejection of blood from the left ventricle) and contrac-
tility of the heart. The ability of the aorta to expand during systole is labelled compliance.
Compliance is directly related to elasticity of the vessels which tends to decrease with age.
This is the mechanism underlying systolic hypertension which develops with ageing.
• Diastolic blood pressure is directly dependant on the amount of blood in the aorta
during diastole which in turn is determined by peripheral vascular resistance and the
heart rate. Increased diastolic pressure is caused by peripheral vasoconstriction,
increase in blood viscosity as in leukaemias and polycythaemia and increase in heart
rate. Factors that cause peripheral vasoconstriction by contracting the arteriolar smooth
muscle include a-adrenergic stimuli (increased circulating catecholamines and
angiotensin II, and increased total body sodium. Excess sodium increases plasma
volume which increases systolic pressure and induces vasoconstriction of arterioles
(increases calcium-mediated contraction of the smooth muscle).

Aetiological Classification of Hypertension

• Hypertension is classified into two types:
• Primary or essential or idiopathic (90–95%): Wherein cause of increased blood pressure
is unknown.
• Secondary hypertension (5–10%): Hypertension secondary to diseases of kidneys,
endocrines or other organs.
• Both primary and secondary hypertension can be benign or malignant:
• Benign hypertension is characterized by a moderate elevation of blood pressure
slowly rising over many years. Patients have a long and asymptomatic life, unless
myocardial infarction or a cerebrovascular accident occurs.
• Malignant hypertension is typically associated with a marked and rapid increase
in blood pressure to 200/120 mm Hg or more. Patients present with papilloedema,
retinal haemorrhages, hypertensive encephalopathy and renal failure. Life expectancy
after diagnosis is generally less than 2 years, if not treated effectively.

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