Pathology - Thrombosis And Embolism Flashcards
Define thrombosis
The formation of a solid mass of blood within the circulatory system
Give some reasons why thrombosis may occur
- abnormalities of the vessel wall (atheroma, direct injury, inflammation)
- abnormalities of blood flow (stagnation, turbulence)
- abnormalities of blood components (smokers, post-partum, post-op)
How do arterial thrombi appear?
Pale, granular, have “lines of Zahn”, lower cell content
How do venous thrombi appear?
Soft, gelatinous, deep red colour, higher cell content
What does lysis of a thrombus involve?
- Complete dissolution of the thrombus
- fibrinolytic system active
- blood flow re-established
- most likely when thrombi are small
What does propagation of a thrombus involve?
- Progressive spread of thrombosis
- thrombus moves distally in arteries, proximally in veins (towards heart)
What is ‘organisation’ of a thrombus?
A reparative process which leads to ingrowth of fibroblasts and capillaries (similar to granulation tissue). The lumen remains obstructed though
What is ‘recanalisation’ of a thrombus?
One or more channels formed through organising thrombus. Blood flow is reestablished but usually incomplete.
How does thrombosis cause embolism?
Part of the thrombus breaks off, travels through the bloodstream and lodges at a different site.
What are the effects of arterial thrombosis?
- ischaemia
- infarction
- other symptoms depend on site and collateral circulation
What are the effects of venous thrombosis?
Congestion, oedema, ischaemia, infarction
Define embolism
The blockage of a blood vessel by solid, liquid or gas at a site distant from its origin
What types of embolism are there?
- thrombo-emboli (these have broken off from a thrombus)
- air
- amniotic fluid
- nitrogen
- medical equipment
- tumour cells
Where do emboli from systemic veins go?
They pass to the lungs and become pulmonary emboli
Where do emboli from the heart go?
Pass via the aorta to renal, mesenteric and other arteries
Where do emboli from an atheromatous carotid artery go?
Pass to the brain
Where do emboli from atheromatous abdominal aorta of?
To arteries of legs
Give some predisposing factors to deep vein thrombosis
- immobility/bed rest
- post-operative
- pregnancy and post-part up
- oral contraceptives
- severe burns
- cardiac failure
- disseminated cancer
How can the risk of deep vein thrombosis be reduced?
Apply stockings with graduated pressure which compress veins, or wear ‘Flowtron’ boots which intermittently inflate, mimicking muscle pump of the calf.
Can deep vein thrombosis be treated?
It cannot be cured, the thrombus can be prevented from growing by using intravenous heparin type drugs then switching to oral warfarin
What are the effects of pulmonary embolism?
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
What is a cerebral embolism?
Condition in which an embolus blocks blood flow through the vessels of the cerebrum, resulting in tissue ischaemia distal to the occlusion
What is fat embolism?
An embolus made up of fatty acids which becomes lodged in a blood vessel and causes ischaemia
