Vascular Disease: Infarction

Question 1

Infarction definition

Answer 1

process of formation of an infarct

Question 2

What is an infarct?

Answer 2

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

Question 3

Give examples of infarction

Answer 3

myocardial and cerebral
pulmonary
bowel
gangrene

Question 4

What does the type of infarction depend on?

Answer 4

colour
age
infection

Question 5

What is colour based on?

give the types and locations

Answer 5

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

Question 6

Age

Answer 6

fresh/old

Question 7

Infection types and causes

Answer 7

septic - caused by septic emboli like vegetation of SBE

bland - aseptic emboli/thrombi

Question 8

Morphology of infarction

where is the exception of this

Answer 8

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

Question 9

Causes of arterial infarction

Answer 9

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

Question 10

Potential outcomes of MI

Answer 10

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

Question 11

Stages of arterial infarction

Answer 11

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

Question 12

Appearance of infarct at 0-12 hours

Answer 12

nothing visible

but with enzyme histochemistry - loss of oxidative enzymes

Question 13

Appearance of infarct at 12-24 hours

Answer 13

mottling - looks pale

coagulative necrosis, oedema and Hg on microscopic level

Question 14

Appearance of infarct at 24-72 hours

Answer 14

soft and pale

Question 15

Appearance of infarct at 3-14 days

Answer 15

hyperaemic border around pale dead muscle

Question 16

Appearance of infarct at 21-56 days

Answer 16

white scar

Question 17

Early complications of MI

Answer 17

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

Question 18

Late complications of MI

Answer 18

chronic LVF

ventricular aneurysn

Question 19

What is gangrene?

Answer 19

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

Question 20

Example of gangrene

Answer 20

infarction of extremities or bowel

Question 21

Many causes of gangrene

Answer 21

thrombus occluding atheromatous ilio-femoral artery

thromboembolism from left side of the heart

Question 22

Cause of appearance of renal infarct

Answer 22

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

Question 23

Causes of cerebral infarct

Answer 23

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

Question 24

What is a cerebral infarct?

Answer 24

ischaemic stroke

example of liquefactive necrosis

Question 25

How do cerebral infarcts heal?

Answer 25

astrocytic gliosis

Question 26

When do venous infarctions occur?

Answer 26

when entire venous drainage from an organ/tissue is and remains completely obstructed

Question 27

Common examples of venous infarction

Answer 27

bowel - volvulus, hernial strangulation
testis - torsion
ovarian - torsion

Question 28

Sequence of events for venous infarctions

Answer 28

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

Question 29

Volvulus definition

Answer 29

loop of intestine twists around itself and the mesentery that supports it, resulting in a bowel obstruction

Question 30

Describe torsion of the testes

Answer 30

tissues around the testicle are not attached well
testes twist around the spermatic chord
cuts off the blood flow to the testicle

Question 31

Factors which affect the development of infarction

Answer 31

vascular occlusion
nature of vascular supply
rate of development of occlusion
type of tissue

Question 32

How does type of tissue affect the development of infarction?
examples

Answer 32

depends on the tissue’s vulnerability to hypoxia (irreversible damage)
eg. neuron 2-3 mins
myocardium 20-40 mins
fibroblasts many hours

Question 33

What is a strangulated hernia?

Answer 33

a hernia that is cutting off the blood supply to the intestines and tissues in the abdomen

Question 34

What is an incarcerated hernia?

Answer 34

tissue that has protruded and cannot return to its normal position without surgical intervention