Vascular Disease: Infarction Flashcards

1
Q

Infarction definition

A

process of formation of an infarct

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2
Q

What is an infarct?

A

area of ischaemic necrosis due to abrupt cessation of the arterial supply/venous drainage

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3
Q

Give examples of infarction

A

myocardial and cerebral
pulmonary
bowel
gangrene

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4
Q

What does the type of infarction depend on?

A

colour
age
infection

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5
Q

What is colour based on?

give the types and locations

A

based on amount of haemorrhage
pale/white: solid organs like heart and spleen
red/haemorrhagic: loose spongy tissue rich in blood supply/dual like lungs

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6
Q

Age

A

fresh/old

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7
Q

Infection types and causes

A

septic - caused by septic emboli like vegetation of SBE

bland - aseptic emboli/thrombi

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8
Q

Morphology of infarction

where is the exception of this

A

ischaemic coagulative necrosis
except the brain
usually wedge shaped with occluded artery at apex and base at periphery
margins: early - poorly defined and slightly haemorrhagic, later - well-defined
scar tissue - inflammatory response and reparative

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9
Q

Causes of arterial infarction

A
thrombotic/embolic
occlusion by:
embolus
atheroma and thrombosis
atheroma with plaque fissure
atheroma
arterial spasm or trauma
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10
Q

Potential outcomes of MI

A

sudden death
survival - infarct replaced by granulation tissue, then fibrous scar
death due to complications during the infarct healing process

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11
Q

Stages of arterial infarction

A

0-12 hours - early stages of cell death
12 - 24 hours - necrotic muscle fibres apparent microscopically
24 - 72 hours - acute inflammatory reaction to dead muscle
3 - 14 days - macrophagic removal of debris and vascular granulation tissue formation
14 - 21 days - fibrous granulation tissue formation
21 - 56 days - scar formation and cicatrisation

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12
Q

Appearance of infarct at 0-12 hours

A

nothing visible

but with enzyme histochemistry - loss of oxidative enzymes

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13
Q

Appearance of infarct at 12-24 hours

A

mottling - looks pale

coagulative necrosis, oedema and Hg on microscopic level

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14
Q

Appearance of infarct at 24-72 hours

A

soft and pale

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15
Q

Appearance of infarct at 3-14 days

A

hyperaemic border around pale dead muscle

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16
Q

Appearance of infarct at 21-56 days

A

white scar

17
Q

Early complications of MI

A

Sudden death due to cardiac dysrhythmia
Sudden death due to acute left ventricular failure
Rupture of myocardium -> haemopericardium
Rupture of papillary muscle -> acute valve failure->LVF
Mural thrombus on infarct -> embolism -> stroke & others
Fibrinous Pericarditis & extension of MI

18
Q

Late complications of MI

A

chronic LVF

ventricular aneurysn

19
Q

What is gangrene?

A

type of necrosis caused by vascular insufficiency following injury or infection
putrefaction of dead tissue

20
Q

Example of gangrene

A

infarction of extremities or bowel

21
Q

Many causes of gangrene

A

thrombus occluding atheromatous ilio-femoral artery

thromboembolism from left side of the heart

22
Q

Cause of appearance of renal infarct

A

Usually due to emboli from L side of heart
Wedge-shaped
Pale area with hyperaemia around
Heals by scar formation

23
Q

Causes of cerebral infarct

A

atherothrombotic in extra-cerebral arteries
embolic
watershed infarct - hypoperfusion and microembolisms

24
Q

What is a cerebral infarct?

A

ischaemic stroke

example of liquefactive necrosis

25
How do cerebral infarcts heal?
astrocytic gliosis
26
When do venous infarctions occur?
when entire venous drainage from an organ/tissue is and remains completely obstructed
27
Common examples of venous infarction
bowel - volvulus, hernial strangulation testis - torsion ovarian - torsion
28
Sequence of events for venous infarctions
Veins become obstructed, usually by extrinsic pressure Tissues become congested with blood, venules and capillaries being engorged with blood which cannot escape Pressure in capillaries and venules rises so high that: Many of them rupture, with leakage of blood Arterial blood cannot enter, so hypoxia ensues Tissues become congested, hypoxic and necrotic
29
Volvulus definition
loop of intestine twists around itself and the mesentery that supports it, resulting in a bowel obstruction
30
Describe torsion of the testes
tissues around the testicle are not attached well testes twist around the spermatic chord cuts off the blood flow to the testicle
31
Factors which affect the development of infarction
vascular occlusion nature of vascular supply rate of development of occlusion type of tissue
32
How does type of tissue affect the development of infarction? examples
depends on the tissue's vulnerability to hypoxia (irreversible damage) eg. neuron 2-3 mins myocardium 20-40 mins fibroblasts many hours
33
What is a strangulated hernia?
a hernia that is cutting off the blood supply to the intestines and tissues in the abdomen
34
What is an incarcerated hernia?
tissue that has protruded and cannot return to its normal position without surgical intervention