Pathophysiology of ischaemia and infarction

Question 1

What are the 4 different kinds of hypoxia?

Answer 1

Hypoxic - low O2 or low PaO2

Anaemic - abnormal blood

Stagnant - abnormal delivery (occlusion/shock)

Cytotoxic - anaerobic metabolism

Question 2

What factors affect O2 supply?

Answer 2

Inspired air
Pulmonary function
Blood constituents
Blood flow
Integrity of vasculature
Tissue mechanics

Question 3

What factors affect O2 demand?

Answer 3

Tissue requirements at baseline

Activity of tissue above baseline

Question 4

How can IHD be caused by O2 supply issues?

Answer 4

Coronary artery atheroma
Cardiac failure
Pulmonary function
Anaemia
Previous MI causing damage

Question 5

How can IHD be caused by demand issues?

Answer 5

High intrinsic demand of heart

Exertion and stress increases this

Question 6

What are some clinical consequences of IHD?

Answer 6

MI
TIA (symptoms of stroke that improve)
Cerebral infarction
Abdominal aortic aneurysm
Peripheral vascular disease
Cardiac failure

Question 7

What is Poiseuilles law?

Answer 7

Flow depends on resistance and diameter of the vessel

Question 8

What are the clinical effects of ischaemia?

Answer 8

Dysfunction
Pain
Physical damage to specialised cells
Cells with low met rates are safer (fat bone)

Question 9

Define infarction

Answer 9

Ischaemic necrosis within a tissue produced by occlusion of either the arterial supply or venous drainage

Question 10

What can cause infarction?

Answer 10

Thrombosis
Embolism
Strangulation
Trauma - ruptured/cut vessel

All stop blood flow

Question 11

What does the degree of infarction depend on?

Answer 11

Time period
Tissue/organ
Pattern of blood supply
Previous disease

Question 12

How long before there is irreversible damage following infarction?

Answer 12

20-30mins

Question 13

Where are pale infarcts seen?

Answer 13

Solid tissues e.g. myocardium, spleen, kidney

24-28hr after

Question 14

Where are red infarcts seen?

Answer 14

Loose tissues e.g. lung, liver

24-48hr after

Question 15

What is reperfusion injury?

Answer 15

tissue damage caused by blood supply returning to tissue after period of ischaemia, which results in inflammation and oxidative damage rather than restoration of normal function

Question 16

Describe the reparative processes seen in the heart following MI

Answer 16

Cell death
Inflammation
Macrophage phagocytosis of dead cells
Granulation tissue
Collagen deposition and scar formation

Question 17

Whats a transmural infarction?

Answer 17

Necrosis affects full thickness of myocardium

Question 18

What is a subendocardial infarction?

Answer 18

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

Question 19

What are some complications of MI

Answer 19

Arrhythmias
Sudden cardiac death
Angina
Cardiac failure
Cardiac rupture
Reinfarction
Pulmonary embolism secondary to DVT
Papillary muscle dysfunction
Mural thrombosis
Ventricular aneurysm
Dresslers syndrome

Question 20

What is Dresslers syndrome?

Answer 20

Dressler’s syndrome is a type of pericarditis — inflammation of the sac surrounding the heart (pericardium). Dressler’s syndrome is 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