Hypertension

Question 1

hypertension epidemiology

Answer 1

Leading global cause of death

Affects 1bn people worldwide

Question 2

Define hypertension

Answer 2

level of blood pressure above which investigation and treatment do more good than harm

Question 3

What is teh distribution of BP and hypertension?

Answer 3

BP distribution is unimodal (one maximum) and any distinction between normal and abnormal is arbitary and has changed overtime.

Question 5

What is ambulatory BP?

Answer 5

Blood pressure automatically recorded at regular interval and averaged to show true mean - 5-10mmHg lower than recorded in surgeries

Question 6

Blood Pressure and age

Answer 6

• Mean BP rises with age
• Pulse pressure rises with age
• Majority of people above 60 will be expected to be hypertensive.

Therefore the number of people diagnosed as hypertensive increases with age, if you live long enough you will almost certainly become hypertensive.

Question 7

What is primary/ essential hypertension?

Answer 7

Primary hypertension has an unidentifiable cause

85-95% of cases

Question 8

What is secondary hypertension?

Answer 8

Hypertension with an identifiable cause. Causes include:

• Renal disease
• Tumors secreting alderostone (to do with sodium reabsorption)
• Tumors secreting catecholamines
• Oral contraceptive pills
• Pre-eclampsia/ pregnancy associated hypertension
• Rare genetic causes

Question 9

(Aetiology) causes of primary hypertension?

Answer 9

Genetic: monogenic (rare), complex polygenic (common)

Environment: dietary salt, obesity, lack of exercise, alcohol, pre-natal environment, pregnancy (pre-eclampsia), other dietary factors

Question 10

Genetics and blood pressure

Answer 10

30-50% of variation in blood pressure is attributable to genetic variation but to date identified SNPs only account for <4% of this variance.

Monogenic disease causes <1% of hypertension: Liddle’s syndrome (mutation in gene coding for Na channel) and Apparent mineralcorticoid excess too.

Complex polygenic cases are much more significant; multiple genes with small effects (positive and negative) and interaction with sex, other genes and environment

Question 11

Blood pressure and age in a low salt environment

Answer 11

Dietary salt intake is a major factor in the rise in BP with age

Question 12

How do you calculate blood pressure (MAP)?

Answer 12

MAP= CO x TPR

In primary hypertension, its mainly due to elevated peripheral resistance.

Question 13

Which factors are associated with established hypertension (in terms of CVS)?

Answer 13

1. Increased TPR
2. Decreased arterial compliance
3. Normal CO
4. Normal blood volume
5. Central shift in volume
6. Secondary to reduced venous compliance

Question 14

What causes elevated TPR in hypertension?

Answer 14

There is active narrowing of the arteries (vasoconstriction)- this is short term

There is structural narrowing of the arteries (growth and remodelling)

Capillary loss (rarefraction)

Question 15

Isolated systolic hypertension

Answer 15

Systolic BP > 140mmHg and diastolic BP < 90mmHg

Systolic high, diastolic normal

This is a condition of people over the age of 60. It is due to the icnreasing stiffness of medium/ large arteries (no real main cause for this)

Pulse wave reflected and is greater by the time it reaches brachial artery.

This does not mean that the TPR increases.

There is no real treatment for ISH vs normal hypertensive treatments

Question 16

Pathological mechanisms behind the causes of primary hypertension

Answer 16

All of the following mechanisms increase TPR.

Kidney: key role in BP regulation - salt intake strongly linked to BP, with low salt leading to no increase with age and low BP (monogenic causes usually related to genes affecting renal Na+ excretion)

Endocrine/ paracrine factors: inconsistence evidence

Sympathetic nervous system: high sympathetic activity to development of hypertension

Question 17

more on the kidney as a cause of hypertension

Answer 17

• Impaired renal function/ perfusion is 2nd commonest cuase of hypertension
• Almost all monogenic causes of hypertension affect renal Na secretion
• And remember people who have a lower salt intake will have no rise with BP with age

Question 18

Hypertension increases the risk of:

Answer 18

• Coronary heart disease
• Stroke
• Peripheral vascular disease
• Heart failure
• Atrail fibrilation
• Dementia/ cognitive impariment
• Retinopathy

Question 19

What does hypertension do to the left ventricle?

Answer 19

Increase in LV wall mass and changes in the chamber size

Question 20

Hypertension and congestive heart failure (CHF)

Answer 20

Prevalence of CHF is increasing (as opposed to other CVD)

Hypertension increases the risk of CHF 2-3 fold and accounts for 25% of all cases of CHF

Hypertension precedes CHF in 90% of cases and most CHF in the elderly is attributable to hypertension

Question 21

Hypertension and large arteries

Answer 21

High BP also results in changes in large arteries (like common carotid arteries). Typically, hypertension is associated with thickened walls (hypertrophy) of large arteries and acceleration of athersclerosis

This is a compensation mechanism to withstand the increased stress on the walls.

Question 22

Consequences of the large arteries?

Answer 22

Hypertension can cause arterial rupture or dilations (aneurysms).

This can lead to thrombosis or haemorrhage (stroke)

Question 23

Hypertension and the eyes

Answer 23

Hypertension adversely affects the microcirculation in the eyes. There will be microvascular damage. The thickening of the walls of small arteriesm, arteriolar narrowing, vasopasm, impaired perfusion and increased leakage into the surrounding tissue (exudates)

Question 24

Hypertension in microcirculation

Answer 24

Hypertension is associated with reduction in capillary density.

Elevated capillary pressure= damage and leakage

Question 25

Hypertension and the kidney

Answer 25

Renal damage/ dysfunction is common in hypertension

Increased microalbumin excretion in urine due to a reduced glomerular filtration rate (also decreases with age, BP speeds up rate)

Primary hypertension: Granular capsular surface, cortical thining, renal atrophy

Accelerated hypertension: subcapsular haemorrhages

Extreme (accelerated) hypertension is now rare but leads to rapidly progessive kindey failure.

Question 26

BP and microalbuminuria

Answer 26

Hypertension causes increased loss of albumin in the urine, it causes reduced glomerular filtration rate.

GFR declines with age even without high BP which speeds up the deteriation.

Question 27

Lifestyle modification for BP

Answer 27

• weight loss
• exercise
• less alcohol
• quit smoking

Question 28

What are treatments for hypertension?

Answer 28

ACE inhibitors- angiotensin II cannot be produced. Less alderostone is secreted, less Na is reabsorbed and BP decreases.

ANGIOTENSIN RECEPTOR BLOCKER- AGII cannot have its effects on target organs. It is vital that this is used as AGII can be made by otherways, bypassing the RAAS system.

Question 29

Another treatment: diuretics

Answer 29

loop dieuretics: Used in hypertensive crisis to block water reabsorption

Thiazide diuretics do not work through diuresis, but slowly reduce PVR (pulmonary vascular resistance)

Question 30

Beta blockers

Answer 30

Blockage of ß1 receptors in heart, reduced rate and force of contraction and there is reduced CO.

Blockage of ß1 receptors in kidney- reduced secretion of renin and reduced RAAS activity.

Question 31

Calcium channel blockers

Answer 31

Major mechanism: in vascular smooth muscle to reduce Ca2+ influx to reduce actin-myosin cross bridge cycling

Minor mechanism: inhibition of Ca influx to reduce contractility (negative inotropy) and rate of conduction (negative dromotropy) in the heart