Pathology of Hypertension

Question 1

Definition of hypertension

Answer 1

Disorder in which the level of sustained arterial pressure is higher than expected for the age, sex, and race of the individual

Question 2

Accepted value of hypertension and flaw?

Answer 2

Greater than 140/90 mmHg

But there is normal variation in BP and around 25% of the population have unknown hypertension

Question 3

Cautions when taking and interpreting BP readings?

Answer 3

Normal variation in individuals at different times of day - REPEAT measurements

WHITE COAT hypertension - nervousness of having BP reading taken

Question 4

Two types of BP, in relation to variation?

Answer 4

Stable - not much variation (more effective remodelling than in labile)

Labile - great variation in readings at different times (likely to be worse in terms of complications)

Question 5

What does hypertension CAUSE?

Answer 5

Cardiac failure

Question 6

Hypertension is a risk factor for?

Answer 6

Cerebral haemorrhage
Atheroma; also, increased rate of progression of that atheroma
Renal failure
Sudden cardiac death

Question 7

Where are when is hypertension more common?

Answer 7

Higher in Black populations
If there is a familial tendency
Rises with age

Question 8

Types of classification of hypertension?

Answer 8

According to cause (aetiological):
Primary
Secondary

According to consequences (clinicopathological):
Benign
Malignant

Question 9

How can BP change?

Answer 9

Changes in CO due to changes in:
HR
Contractility (SV)
Blood volume (SV)

Changes in TPR due to:
Vasoconstrictors, e.g: Ang. II and catecholamines (adrenaline, noradrenaline)
Vasodilators, e.g: NO, certain prostaglandins

Question 10

What do SBP and DBP mean?

Answer 10

SBP - peak BP that coincides with left ventricular ejection

DBP - baseline below which BP does not fall and coincides with left ventricular relaxation

Question 11

What are the resistance arteries?

Answer 11

Arterioles contribute most to TPR

Question 12

Main regulation of the RAAS system?

Answer 12

Mainly, renal blood flow (kidneys and brain auto-regulate blood flow)
If BP decreases, renin is released

Question 13

Function of Ang. II?

Answer 13

First bio-active component of the RAAS system:
Vasoconstrictor

Aldosterone (mineralocorticosteroid) release causes Na+ and water retention to increase blood volume

Question 14

Reason for which RAAS system activity may be high?

Answer 14

Due to polymorphisms in renin, etc

May contribute to familial hypertension

Question 15

What is primary hypertension?

Answer 15

Majority (90%) of cases have NO OBVIOUS CAUSE

Genetic factors are strongly implicated - from twin studies

Question 16

How can protein intake affect BP?

Answer 16

Increased protein intake, increases renal blood flow so more RAAS activity

Question 17

What is salt-sensitive hypertension?

Answer 17

Where an increase in dietary salt increases BP (controlled by a reduced salt diet) - due to genetic polymorphisms

NOT ALL PRIMARY HYPERTENSIVES ARE SALT-SENSITIVE

Question 18

What type of hypertension is normally salt-sensitive?

Answer 18

Hypertension secondary to renal disease

Question 19

What is secondary hypertension?

Answer 19

Underlying disease is implicated, e.g:
Renal disease (most common secondary cause)
Endocrine disease
Aortic disease
Renal artery stenosis
Drug therapy

Question 20

Renal causes of secondary hypertension?

Answer 20

Any renal disease, e.g: diabetic renal disease (almost all diabetics become hypertensive)
Renal artery stenosis
Acute/chronic glomerulonephritis
Chronic pyelonephritis
Cystic diseases
Interstitial nephritis

Question 21

How do renal disease cause hypertension?

Answer 21

Reduced renal blood flow so excess renin release

Salt and water overload increase blood volume

Question 22

Endorcrine causes of hypertension?

Answer 22

Adrenal gland hyperfunction/tumours:

Conn’s Syndrome (primary aldosteronism) - excess aldosterone
Cushing’s syndrome - excess corticosteroid
…adrenal cortex responsible for these two

Phaeochromocytoma - tumour of adrenal medulla leading to excess noradrenaline

Question 23

How does coarctation of the aorta cause hypertension?

Answer 23

Congenital narrowing of segments of the aorta (increase in resistance)

Question 24

Example of drugs which cause hypertension?

Answer 24

Corticosteroids

Question 25

What is benign hypertension?

Answer 25

Remains a cause of serious life-threatening mortality

ASYMPTOMATIC - incidental findings often in health checks

Question 26

Benign hypertension is a risk factor for?

Answer 26

Left ventricular hypertrophy (increased left ventricular load as pumping into a greater resistance)

Congestive cardiac failure

Increases atheroma

Increases aneurysm (sacular dilatations) rupture - aortic dissection, Berry aneurysms (within brain circulation)

Renal disease

Stroke

Question 27

Consequences of left ventricular hypertrophy?

Answer 27

Increased left ventricular load
Poor perfusion (due to thickening, particularly to subendocardial part of the heart)
Interstitial fibrosis
Micro-infarcts (causes small areas of scarring)
Diastolic dysfunction (left ventricle unable to dilate properly, so filling of left ventricle is impaired)

Question 28

Left venticular hypertrophy increases risk of?

Answer 28

Sudden cardiac death - due to arrhythmias and poor perfusion

Cardiac failure

Affects outcomes of other diseases

Question 29

How can hypertrophy due to hypertension be distinguished from hypertrophy due to other causes?

Answer 29

Hypertensive hypertrophy tends to be concentric

Question 30

Consequences of fibrosis in hypertension?

Answer 30

Lots of collagen laid down

Contraction becomes ineffective (as fibrous tissue is not contractile) leading to cardiac failure

Question 31

What are microvascular changes?

Answer 31

Blood vessel wall changes - small arteries and arterioles
Can occur in the retina and kidney

Thickening of media

HYALINE ARTERIOSCLEROSIS - plasma proteins are forced into the vessel walls (thickening)

Question 32

What is malignant hypertension?

Answer 32

Serious life-threatening condition (diastolic 130-140 mmHg)

Can develop from either benign primary or secondary hypertension (“accelerated” hypertension), or arise (rarely) de-novo

Requires urgent treatment to prevent death

Question 33

What does malignant hypertension cause?

Answer 33

Causes cerebral oedema - seen as papilloedema (swelling of optic disc)

Acute renal failure

Acute heart failure

Headache and cerebral haemorrhage

Blood vessels show fibrinoid necrosis (accumulation of amorphous, basic, proteinaceous material in the tissue matrix with a staining pattern reminiscent of fibrin); fibrin is deposited and there is endarteritis proliferans of their walls (marked increased in the fibrous tissue of the intima)

Question 34

Consequences of pregnancy-associated hypertension?

Answer 34

Increased maternal and fetal morbidity and mortality

Can be pre-eclampsia - hypertension associated with protein urea, which resolves following birth
Can sometimes progress to eclampsia (obstetric emergency) - onset of seizures in a women with pre-eclampsia

Question 35

Other causes of hypertension during pregnancy?

Answer 35

Occasionally, in mothers, hypertension secondary to silent renal or systemic disease may be encountered