Pathophysiology of ischaemia and infarction

Question 1

Define ischaemia

Answer 1

restriction in blood supply to tissues, causing a shortage of oxygen that is needed for cellular metabolism

Question 2

define infarction

Answer 2

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

Question 3

How can blood can become stagnant?

Answer 3

abnormal delivery of blood due to:-

• Local effects like occlusion of vessel
• Systemic e.g. shock

Question 4

what 6 factors affect oxygen supply?

Answer 4

1. Inspired O2
2. Pulmonary function
3. Blood constituents
4. Blood flow
5. Integrity of vasculature
6. Tissue mechanisms

Question 5

what 6 factors affect oxygen supply?

Answer 5

1. Inspired O2
2. Pulmonary function
3. Blood constituents
4. Blood flow
5. Integrity of vasculature
6. Tissue mechanisms

Question 6

what 2 factors affect oxygen demand?

Answer 6

Tissue itself - different tissues have different requirements

Activity of tissue above baseline value

Question 7

what is a heart aneurysm?

Answer 7

an atheroma in the aorta

Question 8

Name 6 clinical consequences of ischaemia?

Answer 8

Myocardial infarction
Transient ischaemic attack (TIA- mini stroke)
cerebral infarction 
abdominal aortic aneurysm 
peripheral vascular disease 
cardiac failure

Question 9

what causes infarction

Answer 9

cessation of blood flow

ie thrombosis, embolism, strangulation (gut) or trauma like a cut/ruptured vessel

Question 10

what is the scale of damage of ischaemia/infarction dependent on several factors? (4)

Answer 10

Time period
Tissue/organ
Pattern of blood supply
Previous disease

Question 11

where does coagulative necrosis occur?

Answer 11

heart, lung

Question 12

where does colliquitive necrosis occur?

Answer 12

brain

Question 13

transmural infarction

Answer 13

ischaemic necrosis affects full thickness of the myocardium

Question 14

Subendocardial infarction

Answer 14

ischaemic necrosis mostly limited to a zone of myocardium under the endocardial lining of the heart

Question 15

Dressler’s syndrome

Answer 15

type of pericarditis
- believed to be an immune system response after damage to heart tissue or to the pericardium, from events such as a heart attack, surgery or traumatic injury

Question 16

what is a Transient ischaemic attack (TIA)?

Answer 16

a mini stroke

Question 17

summary of the effects of ischaemia

Answer 17

decreased O2 supply, not meeting the demand of tissues - anaeorobic respiration - cell death - breakdown of tissues

Question 18

end result of infarction

Answer 18

scar replaces area of tissue damage
shape depends on territory of occluded vessel
repurfusion injury (blood flows back after period of ischaemia - may result in a local and systemic inflammatory response that may augment tissue injury in excess of that produced by ischaemia alone)

Question 19

Reparative processes involved in MI (6)

Answer 19

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