Pathophysiology of Thrombus and Embolism

Question 1

How can the flow of normal blood be described?

Answer 1

Normal blood flow is laminar

Question 2

Explain the organisation in which plasma and blood cells travel in relation to the blood vessel

Answer 2

In a vessel, plasma flows along the sides of the blood vessel (beside the lumen) while blood cells travel in the middle of the vessel

Question 3

Which travels the fastest; plasma or blood cells?

Answer 3

Blood cells

Question 4

What is stasis?

Answer 4

Stagnant blood

Question 5

Explain what is meant by the term “turbulent” blood flow

Answer 5

Forceful, unpredictable flow

Question 6

List 7 causes of abnormal blood flow

Answer 6

1. thromboembolism
2. Atheroma
3. Hyperviscocity
4. Spasm
5. External compression
6. Vasculitis
7. Vascular steal

Question 7

What is vasculitis?

Answer 7

Inflammation of the vessel wall

Question 8

what is vascular steal?

Answer 8

When two connected systems are operating at different pressures due to the presence of stenosis - the lower pressure system “steals” blood from the higher pressure system

Question 9

Name the three aspects of virchow’s triad

Answer 9

1. Changes in the blood vessel wall
2. Changes in the blood constituents
3. Changes in the pattern of blood flow

Question 10

What is a thrombus?

Answer 10

A thrombosis is the formation of a solid mass from the constituents of blood within the vascular system during life

Question 11

Is a thrombus the same as a clot?

Answer 11

No

Question 12

Explain the causes of a thrombus in relation to virchows triad

Answer 12

1. Changes in the blood vessel wall (caused by atheroma)
2. Changes in the blood constituents (hyper viscosity or post-traumatic hypercoagulability)
3. Changes in the pattern of blood flow (stagnant blood or turbulent blood caused by atheroma or aneurism)

Question 13

An atheromatous plaque can cause the formation of a thrombus. Explain this process in reference to virchows triad

Answer 13

1. Endothelial injury (e.g. the presence of a preexisiting atheroma)
2. Turbulent blood flow causes the loss of intimal cells and the plaque becomes denuded.
3. the denuded plaque exposes collagen which platelets adhere to (Hypercoagulability of the blood). The platelets form a fibrin meshwork which traps red blood cells. Alternating bands (lines of Zahn) are formed which results in further turbulence and platelet deposition

Question 14

What are the three main consequences of a thrombi

Answer 14

• Deep vein thrombosis
• Ischaemic limbs
• Myocardial infarction

Question 15

What factors determine the consequences associated with a thrombus?

Answer 15

• Where the thrombus is
• The extent of the thrombus
• The collateral circulation

Question 16

Can a thrombus resolve without causing death or disability?

Answer 16

Yes

Question 17

How can a thrombus resolve without causing death or disability?

Answer 17

The thrombus could resolve as a result of organisation or recanalization

Question 18

how does a thrombus cause death/disability?

Answer 18

It breaks off from the site of formation, embolises to a distant site and causes ischaemia and/or infarction

Question 19

Define ‘embolism’

Answer 19

An embolism is the movement of abnormal material in the bloodstream and its impaction in a vessel, blocking its lumen

Question 20

Name the 4 different types of embolism

Answer 20

1. thromboembolism
2. Fat embolus
3. Gas embolus
4. Miscellaneous types

Question 21

What is the most common type of embolus?

Answer 21

thromboembolism

Question 22

What are the 2 most common sites for a systemic thromboembolism to lodge?

Answer 22

Lower limbs and brain `

Question 23

What is a paradoxial emboli?

Answer 23

Paradoxical emboli= when a thrombus crosses an intracardiac defect from the venous blood supply into the into the systemic circulation

Question 24

What are valvular vegetations and what causes them?

Answer 24

lesions, known as vegetations, which is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells form on the heart valves as a result of endocarditis

Question 25

Where do venous thromboemboli origionate form?

Answer 25

DVTs

Question 26

List the 4 possible outcomes of a venous thromboembolus

Answer 26

1. Pulmonary haemorrhage/infarction
2. Right heart failure
3. Sudden death
4. No consequence

Question 27

Where does a venous thromboembolism travel to?

Answer 27

The pulmonary arterial circulation

Question 28

List the risk factors associated with DVT (10)

Answer 28

• Cardiac failure
• Severe trauma/burns
• Post-op/post-partum
• Nephrotic syndrome
• Disseminated malignancy
• Oral contraceptive
• increased age
• Bed rest/immobilisation
• Obesity
• Past medical history of DVT

Question 29

What kind of injury can cause a fat embolis?

Answer 29

Major fractures

Question 30

Which areas of the body tend to be most affected by a fat embolis?

Answer 30

Brain, kidneys & skin

Question 31

Explain briefly what decompression sickness is

Answer 31

N2 forms as bubbles which lodge in the capillaries (gas embolus)

Question 32

List the 6 other materials that can embolise

Answer 32

1. tumour cells
2. Trophoblast material
3. Septic material
4. Amniotic fluid
5. Bone marrow
6. Foreign bodies