Pathophysiology of Ischemia and Infarction Flashcards

1
Q

define ischemia

A

relative lack of blood supply to tissue/organ leading to inadequate o2 supply to meet needs of tissue/organ leading to hypoxia

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2
Q

what is stagnant hypoxia?

A

when there is normal inspiration of o2 but abnormal delivery that can be local or systemic

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3
Q

give two examples of stagnant hypoxia

A

shock

occlusion of a vessel

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4
Q

what is cytotoxic hypoxia?

A

when the inspiration of o2 is normal but it is abnormal at tissue level

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5
Q

give some examples of factors effecting oxygen supply

A
inspired o2
pulmonary function
blood constituents
blood flow
integrity of vasculature
tissue mechanisms
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6
Q

what factors affect oxygen demand?

A

the tissue itself, different tissues have different requirements and the activity of the tissue above a baseline value

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7
Q

name some supply issue that lead to ischemic heart disease

A
> coronary artery atheroma
> cardiac failure
> pulmonary function
> anaemia
> previous MI
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8
Q

what will be the clinical consequence of a stable atheroma in a coronary artery?

A

a stable angina

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9
Q

what is the clinical consequence of a complicated atheroma in a coronary artery?

A

an unstable angina

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10
Q

what is the clinical consequence of an ulcerated plaque?

A

there can be thrombosis and ischemia and infarction

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11
Q

what is the clinical consequence of an atheroma in an aorta?

A

aneurysm

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12
Q

what would the effects be from an atheroma that creates a decrease in blood flow from 4 to 2?

A

it would cause a decrease in flow by 16 fold leading to a decrease in o2 leading to ischemia and infarction

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13
Q

describe the biochemical effects of ischemia

A

there is anaerobic metabolism which leads to cell death due to a build up of lactic acid

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14
Q

what are the cellular effects of ischemia?

A

different tissues have variable o2 requirements and are variably susceptible to ischemia

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15
Q

what could the outcome of ischemia be?

A

there could be no clinical effects
there could be resolution (or therapeutic intervention)
It could lead to infarction

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16
Q

define infarction

A

ischemia necrosis within a tissue/organ in living body produced by occlusion of either the arterial blood supply or venous drainage

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17
Q

what is the aetiology of infarction?

A

cessation of blood flow

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18
Q

give some causes of infarction

A

> thrombosis
embolism
strangulation
trauma

19
Q

give some factors on which the scale of damage of infarction depends

A

> time period
tissue/organ
pattern of blood supply
previous disease

20
Q

where does colliquitive necrosis take place?

21
Q

where does coagulative necrosis take place?

A

the heart and lungs

22
Q

how quickly is the onset of atp depletion from the beginning of anaerobic metabolism in ischemia of the heart?

23
Q

how long does it take the myocardial cells to lose contractibility from the onset of ischemia?

A

less than 2 minutes

24
Q

how long does it take for myocyte necrosis to begin in an MI?

A

20-40 minutes

25
what happens if an infarction has gone on for over an hour?
there is injury to the microvasculature
26
what might you see down an electron microscope 12 hours after an infarction?
swollen mitochondria
27
what tissue will have a pale infarct?
myocardium spleen liver
28
what is the colour of lung and liver infarct?
red
29
what are the microscopic changes of an infarct in 24-48 hours?
there is acute inflammation and loss of specialised cell features
30
what will happen to pale infarct if it continues for 72 hours?
it becomes red around the periphery
31
after 72 hours what will infarction look like microscopically?
chronic inflammation macrophages remove debris granulation tissue fibrosis
32
what replaces the area of tissue damage in an infarction?
a scar
33
describe the reparative process in myocardial infarction
cell death > acute inflammation > macrophage phagocytosis of dead cells > granulation tissue > collagen deposition > scar formation
34
describe the effects of a myocardial infarction at 4-12 hours
> early coagulation necrosis > oedema > haemorrhage
35
describe the effects of a MI at 12-24 hours
> ongoing coagulation necrosis > myocyte changes > early neutraphilic infiltrate
36
what are the effects of a MI at 1-3 days?
> coagulation necrosis > loss of nuclei and striations > brisk neutrophilic infiltrate
37
what are the effects of a MI at 3-7 days?
> disintegration of dead myofibres > dying neutrophils > early phagocytosis
38
what are the effects of a myocardial infarction at 7-10 days?
> well developed phagocytosis | > granulation tissue at margins
39
what are the effects on a MI at 10-14 days?
> well established granulation tissue with new blood vessels | > collagen deposition
40
what will an MI look like at 2-8weeks?
> increased collagen deposition | > decreased cellularity
41
describe a MI at more than 2 months?
dense collagenous scar
42
what is a transmural infarction?
ischemic necrosis affecting the thickness of the myocardium
43
what is a subendocardial infarction?
ischemic necrosis mostly limited to a zone of myocardium under the endocardial lining of the heart