Pathophysiology of Ischaemia and Infarction

Question 1

What is hypoxia?

Answer 1

Deficiency in the amount of oxygen reaching the tissues

Question 2

What are the distinguishing features of hypoxic hypoxia?

Answer 2

• low inspired O2 level

- normal inspired O2 but low PaO2

Question 3

What is the distinguishing feature of anaemic hypoxia?

Answer 3

Normal inspired O2 but abnormal blood

Question 4

What is the distinguishing feature of stagnant hypoxia?

Answer 4

Normal inspired O2 but abnormal delivery - local e.g. occlusion of vessel or systemic e.g. shock

Question 5

What is the distinguishing feature of cytotoxic hypoxia?

Answer 5

Normal inspired O2 but abnormal at tissue level

Question 6

Give 3 factors that affect oxygen supply

Answer 6

• inspired O2
• pulmonary function
• blood constituents
• blood flow
• integrity of vasculature
• tissue mechanism

Question 7

Give 2 factors that affect oxygen demand

Answer 7

1. The tissue itself i.e. type of tissue

2. Activity of tissue above baseline value

Question 8

Do fat cells have a high or low O2 requirement?

Answer 8

Low

Question 9

Do brain and heart cells have a high or low O2 requirement?

Answer 9

High

Question 10

What is atherosclerosis?

Answer 10

Localised accumulation of lipid and fibrous tissue in intima of arteries

Question 11

What would be caused by an established atheroma in a coronary artery?

Answer 11

Stable angina

Question 12

What would be caused by a complicated atheroma in a coronary artery?

Answer 12

Unstable angina

Question 13

What would be caused by ulcerated/fissured plaques?

Answer 13

Thrombosis leading to ischaemia/infarction

Question 14

What would be caused by atheroma in the aorta?

Answer 14

Aneurysm

Question 15

Give 3 common clinical consequences of atheroma

Answer 15

• MI
• TIA
• cerebral infarction
• abdominal aortic aneurysm
• peripheral vascular disease
• cardiac failure
• coronary artery disease

Question 16

What effect does atheroma have on blood flow?

Answer 16

Atheroma reduces radius of lumen so reduces blood flow

Question 17

Give a functional effect of ischaemia

Answer 17

Blood/oxygen supply fails to meet demand - due to decreased supply and/pr increased demand

Question 18

What effect does ischaemia have on metabolism?

Answer 18

Ischaemia results in lower oxygen supply which increases anaerobic metabolism producing the wrong chemicals in cells which causes cell death

Question 19

What type of cells are greatly and quickly affected by ischaemia?

Answer 19

Cells with high metabolic rate e.g. cardiac and brain cells

Question 20

Give 3 clinical effects of ischaemia

Answer 20

• dysfunction
• pain
• physical damage to specialised cells

Question 21

What drugs would be used in the treatment of ischaemia to try to restore blood flow?

Answer 21

Thrombolytic agents

Question 22

What is infarction?

Answer 22

Necrosis within a tissue/organ due to the occlusion of blood supply

Question 23

Give 3 common causes of infarction

Answer 23

• thrombosis
• embolism
• strangulation e.g. gut
• trauma e.g. cut/ ruptured vessel

Question 24

Give 4 factors on which the scale of damage of ischaemia/infarction is dependent on

Answer 24

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

Question 25

What is the most common type of necrosis involved in infarction of most tissue types?

Answer 25

Coagulative

Question 26

What kind of necrosis occurs in brain tissue?

Answer 26

Colliquitive

Question 27

What cells die in myocardial infarction sue to coronary arterial obstruction?

Answer 27

Myocytes

Question 28

How long after an infarction are changes in appearance of the infarcted tissue visible?

Answer 28

24-48 hours

Question 29

In what kind of tissues will a pale infarct occur?

Answer 29

Solid tissues e.g. myocardium, spleen, kidney

Question 30

In what kind of tissues will a red infarct occur?

Answer 30

Loose tissues/previously congested tissue

Question 31

From 72 hours after an infarct onwards, what changes can be seen macroscopically in pale infarcts?

Answer 31

Hyperaemic rim (i.e. yellow/white and red periphery)

Question 32

What is a reperfusion injury?

Answer 32

Damage caused to tissue after the blood supply is restored following ischaemia, due to oxidative damage caused by oxygen free-radicals

Question 33

What are the steps involved in the reparative process for a myocardial infarction?

Answer 33

- cell death - acute inflammation - macrophage phagocytosis of dead cells - granulation tissue formation - collagen deposition (fibrosis) - scar formation

Question 34

What is transmural infarction?

Answer 34

Ischaemic necrosis that affects the full thickness of the myocardium

Question 35

What is subendocardial infarction?

Answer 35

Ischaemic necrosis that is mostly limited to a zone of myocardium under the endocardial lining of the heart

Question 36

Give 2 features on which the effect of an infarction is dependent

Answer 36

- site of infarct, within body and organ - size of infarct - contribution of previous disease/infarction

Question 37

Give 5 complications of myocardial infarction

Answer 37

- sudden death - arrhythmias - angina - cardiac failure - cardiac rupture - reinfarction - pulmonary embolism secondary to DVT - papillary muscle dysfunction - mural thrombosis - ventricular aneurysm - Dressler's syndrome