Week 2 - Pathophysiology of Ischaemia and Infarction

Question 1

What is ischaemia?

Answer 1

lack of blood supply to an organ, leading to lack of O2 supply to that organ, and hypoxia

Question 2

what are some types of hypoxia?

Answer 2

• hypoxic hypoxia (low inspired O2)
• anaemia (not enough haem)
• stagnant hypoxia (normal inspired O2, abnormal delivery)
• cytotoxic hypoxia (tissue cant use o2)

Question 3

What factors affect o2 supply?

Answer 3

• inspired o2,
• pulmonary functions,
• blood flow,
• blood constituents,
• vasculature,
• tissue mechanisms

Question 4

what factors affect o2 demand?

Answer 4

activity of tissue. each tissue is specific - heart and brain has high, fat has low

Question 5

What is ischaemic heart disease?

Answer 5

blood/o2 supply issues due to narrowed heart arteries or pulmonary issues

Question 6

what is stable vs unstable angina?

Answer 6

stable angina is an established atheroma in coronary artery, with ischaemic chest pain on exertion.

unstable angina is same but chest pain at rest.

Question 7

What are the effects of ischaemia?

Answer 7

cells are hypoxic so anaerobic resp. occurs. prod lactate - damages cells - death. leads to damage, dysfunction of cells and pain.

Question 8

Which cells are affected by ischaemia the most?

Answer 8

cells with high metabolic rate. neurons, myocytes, renal tubule.

Question 9

Which cells have a low metabolic rate?

Answer 9

fat, connective tissue, bone

Question 10

What are the outcomes of ischaemia? (4)

Answer 10

• find cause of ischaemia.
• may resolve fully.
• if caused by thrombus, consider thrombolysis.
• may lead to necrosis

Question 11

What is infarction?

Answer 11

death of tissue following ischaemia

Question 12

Why does infarction happen?

Answer 12

hypoxia cases anaerobic metabolism to occur.
leads to cell death as enzymes break down tissue

Question 13

What is coagulative vs colliquative necrosis?

Answer 13

• coagulative is in most tissues.
• colliquative is in brain is tissue broken into very small pieces, drawing fluid into area, leads to soft fluid infarct

Question 14

How long until cells die when ischaemic and on anaerobic metabolism?

Answer 14

seconds until cell death

Question 15

How long until cells die when ischaemic from heart failure?

Answer 15

under 2 minutes

Question 16

How do infarcts appear on a microscope from 0-72 hrs?

Answer 16

swollen mitochondria under microscope in 24hrs.

24-48hrs you see pale infarct on solid tissues, or red infarct if there’s a second blood supply. you see acute inflammation microscopically.

72hrs onwards you see yellow infarct with red periphery. microscopically you see chronic inclammation

Question 17

What is the end scar of an infarction?

Answer 17

granulation tissue and collagen deposition. shape depends on territory of occluded vessel

Question 18

What is reperfusion injury?

Answer 18

after period of ischaemia, blood flow returns. due to lack of o2 and nutrients, inflammation occurs, and o2 and free radicals damage cells.

Question 19

What are the reparative processes that occur in myocardial infarction? How long does it take?

Answer 19

cell death - acute inflammation - macrophage phagocytosis - granulation tissue - collagen deposition by fibroblasts - scar tissue formation
2 months>

Question 20

What is transmural MI?

Answer 20

myocardial infarction through full thickness of the wall

Question 21

What is a STEMI vs NSTEMI?

Answer 21

ST elevated MI and non ST elevated MI.

Question 22

What are the effects of infarction?

Answer 22

depends on site and size, and presence of previous disease. may cause death, dysfunction or pain (angina)

Question 23

What are complications of MI?

Answer 23

• sudden death,
• arrhythmia,
• angina,
• heart failure,
• cardiac rupture (chamber walls or papillary muscle)

Question 24

What is a cardiac rupture?

Answer 24

ventricle/chamber walls or papillary muscle rupture