Vascular Conditions

Question 1

List the 2 reasons why blood clots are rare.

Answer 1

1) laminar flow

2) ‘unsticky’ vascular endothelial cells

Question 2

Define laminar flow.

Answer 2

Cells travel in the centre of arterial vessels, do not touch the endothelial lining. High momentum diffusion and low momentum convection.

Question 3

Define a thrombosis.

Answer 3

Formation of a solid mass (thrombus) from blood constituents in an intact vessel of a living person.

Question 4

List the 3 causes of thrombosis (Virchow’s triad).

Answer 4

1) change in vessel wall
2) change in blood flow
3) change in blood constituents

Question 5

Describe the stages of thrombosis. (4)

Answer 5

1) platelet aggregation
2) clotting cascade triggered
3) fibrin mesh (due to clotting cascade)
4) entrapped RBCs (due to fibrin mesh)

Question 6

Define embolism.

Answer 6

Process of a mass (embolus) carried in the blood through circulation to block a vessel.

Question 7

List 5 causes of embolism.

Answer 7

1) thrombus (most commonly)
2) air (e.g. IV)
3) cholesterol crystal (atheromatous plaque)
4) fat (severe trauma with fractures)
5) amniotic fluid (during 1 in 20,000 labours)

Question 8

What happens if an embolus enters the venous system? (4)

Answer 8

1) travel to vena cava
2) pass through right side of heart
3) pass through pulmonary arteries
4) lodge in pulmonary arterial circulation, which splits down into capillaries
∴ lungs filter for venous emboli

Question 9

What happens if an embolus enters the arterial system? (2)

Answer 9

1) travels downstream of entry point

2) blocks a narrower vessel

Question 10

Define ischaemia.

Answer 10

Reduction of blood flow to tissue.

Question 11

What can occur if ischaemia is resolved?

Answer 11

Reperfusion injury. Restored circulation causes oxidative damage and inflammation.

Question 12

Define infarction.

Answer 12

Reduction of blood flow to tissue, resulting in subsequent death.

Question 13

What usually causes an infarction?

Answer 13

Thrombosis of an artery.

Question 14

What organs are susceptible to infarction?

Answer 14

Organs with end arterial supply (only a single artery supplying them), e.g. kidneys

Question 15

What organs are less susceptible to infarction?

Answer 15

Organs with dual arterial supply (two arteries supplying them)

Question 16

List 3 organs with dual arterial supply.

Answer 16

1) lungs - pulmonary arteries and bronchial arteries
2) liver - hepatic arteries and portal vein
3) brain - circle of Willis

Question 17

Define atherosclerosis.

Answer 17

Formation of atherosclerotic plaques in arteries due to incremental vascular epithelial damage.

Question 18

Define atherothombosis.

Answer 18

Formation of a thrombus from a spontaneously disrupted atherosclerotic plaque.

Question 19

Define occlusive thrombosis.

Answer 19

The formation of a thrombus that completely blocks off a blood vessel.

Question 20

List the 3 main constituents of a plaque.

Answer 20

1) lipids, e.g. cholesterol
2) fibrous tissue
3) inflammatory cells

Question 21

List the 6 main risk factors for atherosclerosis.

Answer 21

1) hyperlipidaemia - main risk factor, lipids damage endothelial cells
2) hypertension
3) smoking - increases blood pressure and damages endothelial cells
4) diabetes
5) increasing age
6) male gender

Question 22

List 5 preventative and therapeutic measures for atherosclerosis.

Answer 22

1) smoking cessation
2) weight loss
3) blood pressure control
4) low dose aspirin
5) statins

Question 23

Where do atherosclerotic plaques tend to form?

Answer 23

Arterial branching points and bifurcations.

Question 24

List 6 complications of atherosclerosis.

Answer 24

1) carotid atheroma
2) cerebral infarct
3) myocardial infarct
4) aortic aneurysm
5) peripheral vascular disease
6) gangrene

Question 25

List the 4 stages of an atheroma.

Answer 25

1) fatty streaks
2) intermediate lesion
3) fibrous plaque
4) plaque rupture

Question 26

What percentage of a vessel wall need to be blocked by an atheroma for symptoms to appear?

Answer 26

50-70% —> critical reduction —> reversible tissue ischaemia.

Question 27

How is the size of an atheroma estimated?

Answer 27

Fractional flow reserve, a ratio of blood pressure proximal and distal to the atheroma. For example a ratio of 0.25 shows the vessel is 75% blocked.

Question 28

What is the main constituent of an arterial thrombus?

Answer 28

Platelets —> white thrombus.

Question 29

What drugs do you prescribe for arterial thrombi?

Answer 29

Anti-platelets.

Question 30

What is the main constituent of a venous thrombi?

Answer 30

Fibrin (fibrin mesh entrapping RBCs) —> red thrombus.

Question 31

What drugs do you prescribe for venous thrombi?

Answer 31

Anti-coagulants.