Aneurysms, hypertension and stroke Flashcards
What is hypertension?
sustained elevation of systolic and diastolic BP (>140/90mmHg)
Whats the difference between primary and secondary hypertension?
- primary (idiopathic) - no identifiable cause
- secondary (to) - renal disease, adrenal tumours, aortic coarction, steroid use
What effect does hypertension have on organs?
- 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
What is hypertensive nephropathy?
- loss of a glomerulus causes atrophy of the nephron
- renal arteries thicken
- glomerulosclerosis
What is hypertensive retinopathy?
- 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
Which vessels control BP?
- 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
How do atheromas form?
- 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
How do we monitor BP?
- 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
What is the RAAS system?
- renin cleaves angiotensinogen into angiotensin I
- Lung capillary endothelia cells secrete ACE, which converts AngI to AngII
What does Angiotensin 2 cause?
- 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
What is an aneurysm?
- 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
What are the 4 main types of aneurysm?
- 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.
Name 3 complications from aneurysms
- rupture
- thrombosis
- thromboembolism
What is a stroke?
- sudden onset of neurological deficit due to cardiovascular cause
- commonest in elderly men
- factors are: hypertension, AF,smoking, diabetes mellitus and high cholesterol
What are the 2 types of stroke?
- Ischaemic (80%) - thromboembolic, primary occlusion of intracerebral artery/arteriole
- Haemorrhagic (20%) - most commonly caused by rupture of cerebral microaneurysm.
What is the ischaemic penumbra?
- 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
What 3 factors affect clinical effects of stroke?
- site
- size
- speed of restoration of circulation/ evacuation of clot
Where can herniation occur due to SOL?
- beneath falx cerebri
- through tentorium cerebelli
- through foramen magnum
What is liquefaction necrosis?
A type of necrosis which results in a transformation of the tissue into a liquid viscous mass
What are Lacunar infarcts?
Small lesions affecting deep penetrating arterioles (in basal ganglia, brainstem etc)
- typically seen in diabetes and/or hypertension
What is TIA?
- 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
What stroke management strategies are there?
- Antiplatelet therapy - aspirin, Clopidogrel, Dipyridamole
- Thrombolysis (best within 3 hours)
- Evacuation of clot
How can we try to prevent stroke?
- Cigarette tax
- Aspirin for those at risk (decreases risk by 25%)
- Decrease salt intake
- Treat AF - warfarin
- Fast recognition of TIA
Name 5 other types of intracranial haemorrhage
- Extradural haemorrhage
- subdural haemorrhage
- subarachnoid haemorrhage
- cerebral contusion
- petechial haemorrhages
What is extradural haemorrhage?
- Haemorrhage outside the dura
- typically parietal due to middle meningeal artery rupture
- common lucid interval after initial consciousness - dura takes time to stretch
What is subdural haemorrhage?
- rupture of veins crossing subdural space
- can be acute due to trauma
- or chronic - typical in dementia due to shrinking
What is subarachnoid haemorrhage?
- rupture of berry aneurysm
- SAH is often considered together with a stroke as it can lead to spasm of cerebral arteries causing damage/death
What is cerebral contusion?
Bruise of brain tissue after trauma
- usually opposite side to where the trauma was
What are petechial haemorrhages?
- obstruction of small arterioles and capillaries
- multiple tiny infarcts from capillary obstruction
- isnt a stroke as it isnt primarily cerebral blood vessels
What is the difference between subarachnoid and subdural haemorrhage?
- SAH - blood is confined between pia/arachnoid and follows contour of brain
- Subdural - clot lies between arachnoid and dural meninges
What is an infarction?
Tissue necrosis due to compromised blood supply
What is a watershed infarction?
- 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
