Ischaemia & Infarction 2

Question 1

Describe the appearance of infarcts within the first 24 hours.

Answer 1

There is not much visible to the naked eye, but swollen mitochondria can be seen on electron microscopy.

Question 2

What is the macroscopic appearance of infarcts in solid tissues like the heart, spleen, and kidney after 24 to 48 hours?

Answer 2

They appear pale.

Question 3

How do infarcts in tissues like the lung and liver appear macroscopically?

Answer 3

They may have a red appearance.

Question 4

Define the microscopic changes seen in infarcts under a light microscope.

Answer 4

Acute inflammation at the edge of the infarct followed by loss of specialized cell features.

Question 5

Describe the changes that occur in infarcts around 72 hours post-insult.

Answer 5

Pale infarcts start to look yellow and white, with a red periphery. Chronic inflammation, granulation tissue, and fibrosis begin to develop.

Question 6

What cellular changes are observed in infarcts under a microscope during chronic inflammation?

Answer 6

Macrophages remove debris, new vessel formation occurs, and fibrosis with deposition of collagen takes place.

Question 7

Describe granulation tissue.

Answer 7

Granulation tissue is a type of healing tissue characterized by chronic inflammatory cells, red blood cell lines, new vessel formation, collagen, and myocytes.

Question 8

What is the end result of tissue damage in infarction?

Answer 8

The end result of tissue damage in infarction is the formation of a scar, which varies in shape depending on the territory of the occluded vessel.

Question 9

Define reperfusion injury.

Answer 9

Reperfusion injury is the damage to tissue that occurs when blood supply returns after a period of ischemia, leading to inflammation and oxidative damage.

Question 10

How does reperfusion injury occur?

Answer 10

Reperfusion injury occurs due to the absence of oxygen and nutrients during ischemia, causing inflammation and oxidative damage when blood supply is restored.

Question 11

Describe the appearance of renal infarcts.

Answer 11

Renal infarcts appear as pale areas in the kidney, often resembling a white shape when the organ is partly opened.

Question 12

What is the characteristic feature of a chronic myocardial infarction?

Answer 12

A chronic myocardial infarction is characterized by dense scar tissue and may show signs of cystic, softer areas due to chro-lipids of necrosis.

Question 13

Describe the process of myocardial infarction from cell death to scar formation.

Answer 13

Cell death, acute inflammation, macrophage phagocytosis, granulation tissue formation, collagen deposition, scar formation.

Question 14

What are the different timescales and changes observed in myocardial infarction progression?

Answer 14

Includes early coagulation necrosis, oedema, haemorrhage, myocyte changes, neutrophilic infiltration, granulation tissue formation, collagen deposition, and scar formation.

Question 15

Define transmural myocardial infarction.

Answer 15

It affects the full thickness of the myocardium, leading to haemo-necrosis throughout the wall.

Question 16

How does the appearance of an infarct change over time under the microscope?

Answer 16

From dense white scarred areas to lighter yellow and white areas initially, then collagenous tissue replacing myocytes.

Question 17

Describe the role of macrophages in myocardial infarction.

Answer 17

They phagocytose dead cells, leading to granulation tissue formation and collagen deposition.

Question 18

What are the reparative processes that occur in myocardial infarction?

Answer 18

Cell death, acute inflammation, macrophage phagocytosis, granulation tissue formation, collagen deposition, scar formation.

Question 19

Describe the histological features of a subendocardial infarct.

Answer 19

Ischaemic necrosis mostly limited to a zone just under the endocardial lining of the heart, followed by granulation tissue stage and fibrosis.

Question 20

What is a non-ST Elevation MI and how is it related to subendocardial infarct?

Answer 20

It is when there is no ST-segment elevation but significantly elevated troponin levels, thought to correlate with subendocardial infarct.

Question 21

Define acute infarcts classification based on ECG changes.

Answer 21

Acute infarcts are classified based on whether there is elevation of the ST segment on the ECG.

Question 22

How are the effects of infarction site-dependent?

Answer 22

Effects can vary within the body and organ, affecting different parts like the conducting system or myocardium.

Question 23

Describe the complications of myocardial infarction.

Answer 23

Complications can be immediate, early, or late, including sudden death, arrhythmia, angina, and cardiac failure.

Question 24

What factors influence the repair time of a subendocardial infarct compared to a transmural infarct?

Answer 24

The repair time may be slightly shortened due to less thick damage in a subendocardial infarct.