Aneurysms, hypertension and stroke

Question 1

What is hypertension?

Answer 1

sustained elevation of systolic and diastolic BP (>140/90mmHg)

Question 2

Whats the difference between primary and secondary hypertension?

Answer 2

• primary (idiopathic) - no identifiable cause

- secondary (to) - renal disease, adrenal tumours, aortic coarction, steroid use

Question 3

What effect does hypertension have on organs?

Answer 3

• Heart - LV hypertrophy, left heart failure
• Lungs - pulmonary oedema from LHF
• Kidneys - nephrosclerosis, renal failure
• eye - retinal capillary damage, haemorrhages, exudates
• Brain - microaneurysms, stroke, ischaemia, dementia
• BVs - atheroma

Question 4

What is hypertensive nephropathy?

Answer 4

• loss of a glomerulus causes atrophy of the nephron
• renal arteries thicken
• glomerulosclerosis

Question 5

What is hypertensive retinopathy?

Answer 5

• Early - nicking of retinal veins by overlying arterioles
• moderate - flame shaped haemorrhages; cotton wool spots; hard exudates around macula; straightened, wider capillaries.
• Late - papilloedema, haemorrhage

Question 6

Which vessels control BP?

Answer 6

• BP is controlled by the arterioles, they are the resistance vessels which can constrict or relax to alter the TPR
• Change in lumen’s diameter is the most important factor
• a 50% decrease in diameter gives a 16-fold increase in pressure

Question 7

How do atheromas form?

Answer 7

• resistance arterioles show elastic duplication
• damaged arterioles leak plasma into the vessel wall and cause hardening of the media
• shear force appiled by high pressure CO on endothelium - likely to develop atheroma

Question 8

How do we monitor BP?

Answer 8

• Baroreceptors in the carotid sinus sense stretch, stimulates vasodilation/constriction in response
• chemoreceptors in the carotid and aortic bodies respond to reduced oxygen tension, increased CO2 and increased hydrogen ions
• RAAS system - renin released by juxtoglomerular complex

Question 9

What is the RAAS system?

Answer 9

• renin cleaves angiotensinogen into angiotensin I

- Lung capillary endothelia cells secrete ACE, which converts AngI to AngII

Question 10

What does Angiotensin 2 cause?

Answer 10

• constriction of resistance vessels
• stimulate aldosterone and ADH release - increase water reabsorption by kidney
• stimulate thirst
• stimulate cardiac hypertrophy
• increase NA release and decrease reuptake - enhances sympNS

Question 11

What is an aneurysm?

Answer 11

• bulge in the BV wall
• true aneurysm is when the entire wall bulges
• false aneurysm is when the artery wall is punctured and blood tracks out into adjacent tissue - expands as further blood is pumped out

Question 12

What are the 4 main types of aneurysm?

Answer 12

• Berry (typically occur at the bifurcations of CoW arteries. Rupture causes subarachnoid haemorrhage)
• Abdominal aortic aneurysm (secondary to atheroma - cause ischaemia by throwing off thromboemboli, intraperitoneal haemorrhage and death)
• Microaneurysm (cereberal arteries of hypertensive patients - causes intracerebral haemorrhage if rupture)
• Stretched aortic ring - due to aortic dissection, syphilitic aneurysm.

Question 13

Name 3 complications from aneurysms

Answer 13

• rupture
• thrombosis
• thromboembolism

Question 14

What is a stroke?

Answer 14

• sudden onset of neurological deficit due to cardiovascular cause
• commonest in elderly men
• factors are: hypertension, AF,smoking, diabetes mellitus and high cholesterol

Question 15

What are the 2 types of stroke?

Answer 15

• Ischaemic (80%) - thromboembolic, primary occlusion of intracerebral artery/arteriole
• Haemorrhagic (20%) - most commonly caused by rupture of cerebral microaneurysm.

Question 16

What is the ischaemic penumbra?

Answer 16

• the core of an infarct will undergo irreversible necrosis
• adjacent territory is only relatively ischaemic - may get compensation from nearby vessels
• if we can restore perfusion within 3 hrs, penumbra territory may be salvaged

Question 17

What 3 factors affect clinical effects of stroke?

Answer 17

• site
• size
• speed of restoration of circulation/ evacuation of clot

Question 18

Where can herniation occur due to SOL?

Answer 18

• beneath falx cerebri
• through tentorium cerebelli
• through foramen magnum

Question 19

What is liquefaction necrosis?

Answer 19

A type of necrosis which results in a transformation of the tissue into a liquid viscous mass

Question 20

What are Lacunar infarcts?

Answer 20

Small lesions affecting deep penetrating arterioles (in basal ganglia, brainstem etc)
- typically seen in diabetes and/or hypertension

Question 21

What is TIA?

Answer 21

• Transient ischaemic attack - neurological deficit lasting less than 12-24hrs
• 30% likelihood of stroke in next 5 years
• 4-20% within 90 days
• Factors: age, BP, diabetes

Question 22

What stroke management strategies are there?

Answer 22

• Antiplatelet therapy - aspirin, Clopidogrel, Dipyridamole
• Thrombolysis (best within 3 hours)
• Evacuation of clot

Question 23

How can we try to prevent stroke?

Answer 23

• Cigarette tax
• Aspirin for those at risk (decreases risk by 25%)
• Decrease salt intake
• Treat AF - warfarin
• Fast recognition of TIA

Question 24

Name 5 other types of intracranial haemorrhage

Answer 24

• Extradural haemorrhage
• subdural haemorrhage
• subarachnoid haemorrhage
• cerebral contusion
• petechial haemorrhages

Question 25

What is extradural haemorrhage?

Answer 25

• Haemorrhage outside the dura
• typically parietal due to middle meningeal artery rupture
• common lucid interval after initial consciousness - dura takes time to stretch

Question 26

What is subdural haemorrhage?

Answer 26

• rupture of veins crossing subdural space
• can be acute due to trauma
• or chronic - typical in dementia due to shrinking

Question 27

What is subarachnoid haemorrhage?

Answer 27

• rupture of berry aneurysm

- SAH is often considered together with a stroke as it can lead to spasm of cerebral arteries causing damage/death

Question 28

What is cerebral contusion?

Answer 28

Bruise of brain tissue after trauma

- usually opposite side to where the trauma was

Question 29

What are petechial haemorrhages?

Answer 29

• obstruction of small arterioles and capillaries
• multiple tiny infarcts from capillary obstruction
• isnt a stroke as it isnt primarily cerebral blood vessels

Question 30

What is the difference between subarachnoid and subdural haemorrhage?

Answer 30

• SAH - blood is confined between pia/arachnoid and follows contour of brain
• Subdural - clot lies between arachnoid and dural meninges

Question 31

What is an infarction?

Answer 31

Tissue necrosis due to compromised blood supply

Question 32

What is a watershed infarction?

Answer 32

• if BP suddenly drops, tissue at the periphery of adjacent arterial territories may be starved of oxygen and infarct
• eg. splenic flexure of colon and watershed zones of CoW