Pathology - Thrombosis And Embolism

Question 1

Define thrombosis

Answer 1

The formation of a solid mass of blood within the circulatory system

Question 2

Give some reasons why thrombosis may occur

Answer 2

• abnormalities of the vessel wall (atheroma, direct injury, inflammation)
• abnormalities of blood flow (stagnation, turbulence)
• abnormalities of blood components (smokers, post-partum, post-op)

Question 3

How do arterial thrombi appear?

Answer 3

Pale, granular, have “lines of Zahn”, lower cell content

Question 4

How do venous thrombi appear?

Answer 4

Soft, gelatinous, deep red colour, higher cell content

Question 5

What does lysis of a thrombus involve?

Answer 5

• Complete dissolution of the thrombus
• fibrinolytic system active
• blood flow re-established
• most likely when thrombi are small

Question 6

What does propagation of a thrombus involve?

Answer 6

• Progressive spread of thrombosis

- thrombus moves distally in arteries, proximally in veins (towards heart)

Question 7

What is ‘organisation’ of a thrombus?

Answer 7

A reparative process which leads to ingrowth of fibroblasts and capillaries (similar to granulation tissue). The lumen remains obstructed though

Question 8

What is ‘recanalisation’ of a thrombus?

Answer 8

One or more channels formed through organising thrombus. Blood flow is reestablished but usually incomplete.

Question 9

How does thrombosis cause embolism?

Answer 9

Part of the thrombus breaks off, travels through the bloodstream and lodges at a different site.

Question 10

What are the effects of arterial thrombosis?

Answer 10

• ischaemia
• infarction
• other symptoms depend on site and collateral circulation

Question 11

What are the effects of venous thrombosis?

Answer 11

Congestion, oedema, ischaemia, infarction

Question 12

Define embolism

Answer 12

The blockage of a blood vessel by solid, liquid or gas at a site distant from its origin

Question 13

What types of embolism are there?

Answer 13

• thrombo-emboli (these have broken off from a thrombus)
• air
• amniotic fluid
• nitrogen
• medical equipment
• tumour cells

Question 14

Where do emboli from systemic veins go?

Answer 14

They pass to the lungs and become pulmonary emboli

Question 15

Where do emboli from the heart go?

Answer 15

Pass via the aorta to renal, mesenteric and other arteries

Question 16

Where do emboli from an atheromatous carotid artery go?

Answer 16

Pass to the brain

Question 17

Where do emboli from atheromatous abdominal aorta of?

Answer 17

To arteries of legs

Question 18

Give some predisposing factors to deep vein thrombosis

Answer 18

• immobility/bed rest
• post-operative
• pregnancy and post-part up
• oral contraceptives
• severe burns
• cardiac failure
• disseminated cancer

Question 19

How can the risk of deep vein thrombosis be reduced?

Answer 19

Apply stockings with graduated pressure which compress veins, or wear ‘Flowtron’ boots which intermittently inflate, mimicking muscle pump of the calf.

Question 20

Can deep vein thrombosis be treated?

Answer 20

It cannot be cured, the thrombus can be prevented from growing by using intravenous heparin type drugs then switching to oral warfarin

Question 21

What are the effects of pulmonary embolism?

Answer 21

Three grades of severity:

• massive PE (more than 60% reduction in blood flow) is rapidly fatal
• major PE (medium sized vessels blocked), patients short of breath, may have a cough and blood stained sputum
• minor PE (small peripheral pulmonary arteries blocked), asymptomatic or minor shortness of breath

Question 22

What is a cerebral embolism?

Answer 22

Condition in which an embolus blocks blood flow through the vessels of the cerebrum, resulting in tissue ischaemia distal to the occlusion

Question 23

What is fat embolism?

Answer 23

An embolus made up of fatty acids which becomes lodged in a blood vessel and causes ischaemia