Thrombus, Embolism And Atherloscerosis

Question 1

What is a thombus?

Why do thrombus occur?

Answer 1

• Formation of a solid mass of blood within circulatory system.
• Virchow’s Triad …

1. Defects of vessel walls
   - atheroma
   - direct injury
   - inflammation
2. Abnormalities of flow
   - stasis - e.g.: due to narrowing of vessel or low bp
   - turbulent flow - e.g.: due to stenosis
3. Abnormalities in blood components
   - smokers (hyper coagulable state)
   - after giving birth
   - after operations

Question 2

What do thrombi look like in arteries?

Answer 2

• pale (less RBCs within)
• granular
• lines of zhan (colour depends on composition of blood at that time)
• lower cell content

Question 3

What do thrombi look like in veins?

Answer 3

• soft
• gelatinous
• deep red as higher red cell content

Question 4

What can the outcomes of a thrombus be? (4)

Answer 4

1) lysis - when thrombi are small, complete dissolution by fibrinolytic system + establishment of blood flow
2) propagation - spread and growth of thrombi, distal in arteries, proximal in veins
3) organisation - repair with granulation like tissue- still obstructs lumen
4) Recanalisation - one or more channels form allowing limited flow through thrombus
5) Embolism

Question 5

What is an embolism?

Answer 5

The blockage of a blood vessel by solid, liquid or gas at a distant site to its origin - when thrombus breaks off and travels through bloodstream.

Question 6

What is the consequence of a venous thrombo- emboli?

What is the consequence of an arterial thrombi-emboli?

Answer 6

• congestion of veins
• oedema- fluids cannot be exchanged as easily
• ischaemia and infarction as blood cannot flow as easily
• Ischaemia + infarction (depends on site + collateral circulation)

Question 7

What other substances can cause embolisms?

Answer 7

• air (need 15ml to have effect, makes blood throthy so cant pump as well)
• amniotic fluid
• nitrogen (from dissolved N2 becoming gaseous in decompression syndrome)
• medical equipment
• tumour cells
• fat + bone marrow

Question 8

What are the risk factors for DVTs?

Answer 8

Immobility
Post op
Pregnancy
Burns 
Oral contraceptives 
Disseminated cancer

Question 9

How can DVT be treated?

Answer 9

• TED stockings
• ‘flowtron boots’ which periodically inflate
• oral warfarin (wont lyse thrombus but will prevent growth)
• IV type heparin (again wont lyse)

Question 10

What is a straddle embolism?

Answer 10

One that straddles the bifurcation of a pulmonary trunk

Question 11

What are symptoms of major and massive pulmonary embolism?

Answer 11

Massive- 60% of blood flow to lungs occluded, rapid death

Major: short of breath, coughing, blood stained sputum

Question 12

What is an iatrogenic embolism?

Answer 12

Embolism resulting from treatment

Air embolism or medical equipment

Question 13

What do fat emboli most commonly occcur?

Answer 13

After closed fractures

Question 14

What are the preventative and treatment options for thrombosis and thromboembolism?

Answer 14

• low molecular weight heparin (SC), mobilise early and TED stockings for prophylaxis in high risk patients.
• Clot busters, LMW heparin (e.g.: apixaban), oral warfarin

Question 15

What is atheroma?
What is atherosclerosis?
What is arteriosclerosis?

Answer 15

• The accumulation of intracellular and extracellular lipid in the tunica intima and media of large and medium sized arteries
• Thickening and hardening of arterial walls as a consequence of atheroma
• The thickening of arterial walls and arterioles due to hypertension or DM.

Question 16

What does an atheroma start off as?

Answer 16

Starts off as fatty streak
Lipid deposits in intima, looks yellow and slightly raised
Do not always go on to form plaques

Question 17

What is the difference between a simple plaque and complicated plaque?

Answer 17

• Simple is a yellow raised larger area with irregular outline
• A complicated one is where plaque has complications, eg thrombosis, haemorrhage, calcification, aneurism ect

Question 18

Where are atheroma most common?

Answer 18

Any arteries except in arms

• aorta
• coronary arteries
• carotid artery
• cerebral arteries
• leg arteries

Question 19

Describe the microscopic changes that occur in the formation of an atherosclerotic plaque?

Answer 19

Early:
- proliferation of smooth muscle cells 
- extracellular lipid and foam cell accumulation 
Late: 
- fibrosis 
- necrosis
- cholesterol clefts (holes where extracellular lipids dissolved away)
Even later:
- calcification 
- elastic laminar disruption 
- damage to media due to pressure from plaque 
- ingrown of blood vessels 
- plaque ruptures surface (fissuring)
- thrombus

Question 20

What is arteriosclerosis?

Answer 20

Hardening of the media in microvasculature due to hypertension with no fat deposits

Question 21

What is aneurysms and how do they occur?

Answer 21

• abnormal dilitation of a blood vessel wall

- media damage means less tension able to be put on blood vessel meaning it expands

Question 22

Where is mesneteric ischaemia? Where is it most commonly seen?

Answer 22

Atherosclerosis of mesenteric artery
Usually seen at splenic flexure where collateral blood supply is worst
Leads to malabsorption ect

Question 23

What is intermittent claudication?

Answer 23

Pain in calfs on walking which goes away after rest but will come back after progressively shorter periods of walking. It is a part of peripheral vascular disease

Question 24

List the major risk factors for atherloslcerosis

Answer 24

• Older age
• Men (women protected till menopause)
• hyperlipidaemia
• cigarette smoking
• hypertension
• diabetes
• alcohol (small amounts are protective)
• infection
• Genetics
• lack of exersize
• obesity
• soft water
• oral contraceptives
• stress

Question 25

What are the signs of a genetic predisposition to atherlosclerosis (familial hyperlipidaemia)?

Answer 25

• arcus (yellow corneum)

- xantheromas (macrophage filled plaques on skin surface- typically over joints)

Question 26

What is the thrombogenic theory for atheroma formation?

Answer 26

• plaques form from repeated thrombi
• the lipid comes from the thrombi
• a fiberous cap forms on top

Question 27

What in insudation theory”?

Answer 27

Endothelial injury
Leads to inflammation
increases permeability to lipid from plasma

Question 28

What is the reaction to injury hypothesis?

Answer 28

• plaques from as a result of endothelial injury
• high cholesterol could cause this damage due to oxidation
• Injury allows high permeability and platelet adhesion
• monocytes penetrate epithelium
• smooth muscle cells proliferate and migrate to intima

Question 29

What is the monoclonal hypothesis for atheroma formation?

Answer 29

• each plaque is a benign tumour of smooth muscle cell proliferation

Question 30

Describe the unifying hypothesis for atheroma formation.

Answer 30

• endothelial injury (due to high LDL, toxins, hypertension, haemodynamic stress)
• This causes platelet adhesion and platelet derived GF release leading to smooth muscle proliferation and migration into the intima
• and also leads to accumulations of lipids and uptake of these makes foam cells- which release cytokines for further smooth muscle cell proliferation and other inflammatory cells
• and also to migration of monocytes into intima
• Smooth muscle cells also stimulated to produce more matrix

Question 31

How can atherosclerosis be prevented?

Answer 31

• decrease smoking
• decrease fat intake
• treat hypertension
• decrease alcohol
• regular exersize and weight control
• lipid lowering drugs like statins