Vascular Pathology 2 - Thrombosis, Embolism, Ischaemia, Infarction

Question 1

What is ischaemia?

Answer 1

A deficiency, real or relative, of oxygenated blood in a tissue causing a shortage of oxygen and impaired aerobic respiration

Question 2

What is ischaemia due to?

Answer 2

Either increased demand for oxygen that is not met, local vascular narrowing or occlusion, or a systemic reduction in tissue perfusion

Question 3

What happens in chronic ischaemia?

Answer 3

The decreased oxygen lasts for months to years and results in cell and tissues atrophying and dying - often results in fibrosis and extra collagen deposition and healing will be impaired due to lack of good blood supply

Question 4

Where does chronic ischaemia commonly occur?

Answer 4

In the kidney due to arteriolosclerosis, in the heart, in the legs due to peripheral vascular disease

Question 5

What happens in acute ischaemia?

Answer 5

The decreased oxygen lasts for minutes to hours - will lead to impaired function and may cause pain - often occurs due to increased demand

Question 6

Where does acute ischaemia commonly occur?

Answer 6

The heart (angina), the legs (claudication), the brain (TIA)

Question 7

What is angina?

Answer 7

Pain in the chest associated with poor blood supply to the heart

Question 8

What is claudication?

Answer 8

Pain in the skeletal muscles with increased exertion causing an increased oxygen demand so causes acute ischaemia - similar to angina

Question 9

What is a TIA?

Answer 9

A transiet ischaemic attack - generally due to an embolism occlusion that is not long enough to cause infarction

Question 10

What is an infarction?

Answer 10

An area of necrosis caused by acute ischaemia

Question 11

What are the causes of infarction?

Answer 11

thrombotic arterial occlusion, embolic arterial occlusion, external compression of artery in dissection, vasospasm of artery, venous occlusion, systemic reduction in tissue perfusion, compartment syndrome

Question 12

What are the two types of infarction?

Answer 12

Pale (anaemic) or red (haemorrhagic)

Question 13

What type of necrosis occurs in infarction?

Answer 13

Coagulative necrosis

Question 14

How do infarcts heal?

Answer 14

By organisation (except in the brain)

Question 15

What does the size of the infarct from arterial occlusion depend on?

Answer 15

The size of the artery occluded, the duration of the occlusion, the vulnerability of the cells to occlusion, whether the artery is carrying oxygenated or deoxygenated blood, the nature of the arterial supply, the oxygen content of the blood, the state of systemic circulation

Question 16

When does a pale infarct occur?

Answer 16

Due to the blockage of an end artery

Question 17

Where do pale infarcts occur?

Answer 17

In the spleen, kidney and the heart mostly and the brain

Question 18

What is the shape of a pale infarct?

Answer 18

Wedge shaped with the base of the wedge along the outer part of the organ

Question 19

When do haemorrhagic infarcts occur?

Answer 19

Usually related to dual circulation, reperfusion, venous occlusion - when blood comes in to dead area

Question 20

Where do haemorrhagic infarcts occur?

Answer 20

In the lung, in the bowel, in the brain

Question 21

What is the shape of haemorrhagic infarcts?

Answer 21

Wedge shaped

Question 22

What does an infarction look like histologically?

Answer 22

Initally (6-12 hours), cells become hypereosinophilic and can just see the cell outline - after time there is acute inflammation and lots of neutrophils come in and then after 1-2 weeks there is granulation tissue and then scarring

Question 23

Why do abnormalities of haemostasis occur?

Answer 23

Because of problems with platelets, the coagulation cascade or vessel walls

Question 24

What is the role of the endothelium in inhibiting thrombosis?

Answer 24

• prostacyclin and NO impede platelet adhesion and vasodilate
  • adenosine diphosphatase - degrades ADP to inhibit platelet aggregation
  • heparin like molecules - cofactors that enhance inactivation of thrombin
  • thrombomodulin - binds to thrombin and converts it to an anticoagulant
  • tissue factor pathway inhibitor - inhibits tissue factor
  • tissue type plasminogen activator (tPA) - cleaves plasminogen to form plasmin which cleaves fibrin to degrade thrombi

Question 25

What are the three causes of thrombosis in Virchow’s triad?

Answer 25

Endothelial dysfunction or injury, hypercoagulability of blood, changes in blood flow

Question 26

How does endothelial dysfunction lead to thrombosis?

Answer 26

Expsoure of collagen, exposure of tissue factor, disruption of balance of production of pro and anti thrombotic factors

Question 27

What are some causes of endothelial dysfunction?

Answer 27

direct trauma, atherosclerosis, infection

Question 28

What are some causes of hypercoagulability?

Answer 28

post operative state, post traumatic state, factor V leiden mutation, prothrombin mutation, malignancies, high oestrogen levels, antiphospholipid antibody syndrome, obesity, post MI

Question 29

How do changes in blood flow lead to thrombosis?

Answer 29

More platelets come in to contact with epithelium, either by turbulence or slowing

Question 30

What are some causes of change in blood flow?

Answer 30

aneurysms, poor muscle pumps, atrial fibrillation

Question 31

What will happen to a thrombus?

Answer 31

Embolism, spontaneously lyse, organisation, remain in one spot

Question 32

What are the lines of Zahn?

Answer 32

Characteristic thrombi that occur in atrial fibrillation

Question 33

What are the different types of emboli?

Answer 33

thombo-emboli, athero-emboli, septic emboli, tumor emboli, air emboli, gaseous nitrogen bubbles, fat and marrow emboli, amniotic fluid

Question 34

What is gangrene?

Answer 34

Necrosis that is complicated by saprophytic bacterial infection - makes the tissue black

Question 35

What is primary gangrene?

Answer 35

gas gangrene - caused by clostridium usually due to infection after trauma

Question 36

What is secondary gangrene?

Answer 36

Infection after the tissue is already necrotic

Question 37

What are the two types of secondary gangrene?

Answer 37

Dry gangrene and wet gangrene

Question 38

What is dry gangrene?

Answer 38

Peripheral vascular disease causes necrosis in the toes/feet/legs and then get a saprophytic infection

Question 39

What is wet gangrene?

Answer 39

Occurs in the internal organs - e.g. complicating acute appendicitis or cholecystitis or infarction of small bowel