Thrombosis and Embolism

Question 1

Define thrombosis

Answer 1

Thrombosis is the formation of a solid mass of blood within the circulatory system (during life)

Question 2

What are some anti-thrombotic factors?

Answer 2

– plasminogen activators
– prostacyclin
– nitric oxide
– thrombomodulin

Question 3

Why does thrombosis occur?

Answer 3

Abnormalities of the vessel wall:

– atheroma (arterial))
– direct injury
– inflammation (e.g vasculitis)

Abnormalities of blood flow:

– stagnation (e.g. DVT, inadequate calf muscle pumping)
– turbulence

Abnormalities of blood components:

– smokers (more coagulative blood)
– post-partum
– post-op

Question 4

How may the appearance of venous and arterial thrombi differ?

Answer 4

Arterial thrombi are pale and granular with lines of zahn and lower cell content.

Venous thrombi are soft and gelatinous with higher cell content.

Question 5

Describe the lysis outcome of thrombosis

Answer 5

– complete dissolution of thrombus
– fibrinolytic system active
– bloodflow re-established
– most likely when thrombi are small

Question 6

Describe the propagation outcome of thrombosis

Answer 6

progressive spread of thrombosis

– distally in arteries
– proximally in veins (thrombus gets bigger going towards the heart as veins become larger)

Question 7

Describe the organisation outcome of thrombosis

Answer 7

– reparative process
– ingrowth of fibroblasts and capillaries (similar to granulation tissue)
– lumen remains obstructed

Question 8

Describe the recanalisation outcome of thrombosis

Answer 8

bloodflow re-established but usually incompletely

– one or more channels formed through organising thrombus

Question 9

Describe the embolism outcome of thrombosis

Answer 9

– part of thrombus breaks off
– travels through bloodstream
– lodges at distant site

Question 10

Describe the arterial and venous effects of thrombosis

Answer 10

• Arterial

– ischaemia
– infarction
– depends on site and collateral circulation

• Venous

– congestion
– oedema
– ischaemia
– infarction

Question 11

Define embolism

Answer 11

Embolism is the blockage of a blood vessel by solid, liquid or gas at a site distant from its origin.

> 90% of emboli are thrombo-emboli

Question 12

List some types of embolism

Answer 12

– air
– amniotic fluid
– nitrogen
– medical equipment
– tumour cells

Question 13

Describe the passage of thrombi-emboli from different points in the body

Answer 13

• from systemic veins pass to the lungs =pulmonary emboli
• from the heart pass via the aorta to renal, mesenteric, and other arteries
• from atheromatous carotid arteries pass to the brain
• from atheromatous abdominal aorta pass to arteries of the legs

Question 14

What is deep vein thrombosis and where can it occur?

Answer 14

Deep vein thrombosis, or deep venous thrombosis, (DVT) is the formation of a blood clot (thrombus) within a deep vein

Upper limb:

Brachial vein
Axillary vein
Subclavian vein

Lower limb:

Common femoral vein
Femoral vein
Profunda femoris vein
Popliteal vein
Peroneal vein
Anterior tibial vein
Posterior tibial vein

Question 15

What are predisposing factors for deep vein thrombosis?

Answer 15

– immobility/bed rest
– post-operative
– pregnancy and post-partum 
– oral contraceptives 
– severe burns 
– cardiac failure 
– disseminated cancer

Question 16

How is deep vein thrombosis prevented and treated?

Answer 16

high risk patients must be identified and offered prophylaxis

– heparin sub-cutaneously
– leg compression during surgery

treatment is:

• intravenous heparin
• oral warfarin

Question 17

What are the effects of pulmonary embolism?

Answer 17

massive PE >60% reduction in blood flow rapidly fatal

major PE - medium sized vessels blocked.

Patients short of breath +/- cough and bloodstained sputum

minor PE - small peripheral pulmonary arteries blocked. Asymptomatic or minor shortness of breath

recurrent minor PEs lead to pulmonary hypertension