Vascular Conditions Flashcards
List the 2 reasons why blood clots are rare.
1) laminar flow
2) ‘unsticky’ vascular endothelial cells
Define laminar flow.
Cells travel in the centre of arterial vessels, do not touch the endothelial lining. High momentum diffusion and low momentum convection.
Define a thrombosis.
Formation of a solid mass (thrombus) from blood constituents in an intact vessel of a living person.
List the 3 causes of thrombosis (Virchow’s triad).
1) change in vessel wall
2) change in blood flow
3) change in blood constituents
Describe the stages of thrombosis. (4)
1) platelet aggregation
2) clotting cascade triggered
3) fibrin mesh (due to clotting cascade)
4) entrapped RBCs (due to fibrin mesh)
Define embolism.
Process of a mass (embolus) carried in the blood through circulation to block a vessel.
List 5 causes of embolism.
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)
What happens if an embolus enters the venous system? (4)
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
What happens if an embolus enters the arterial system? (2)
1) travels downstream of entry point
2) blocks a narrower vessel
Define ischaemia.
Reduction of blood flow to tissue.
What can occur if ischaemia is resolved?
Reperfusion injury. Restored circulation causes oxidative damage and inflammation.
Define infarction.
Reduction of blood flow to tissue, resulting in subsequent death.
What usually causes an infarction?
Thrombosis of an artery.
What organs are susceptible to infarction?
Organs with end arterial supply (only a single artery supplying them), e.g. kidneys
What organs are less susceptible to infarction?
Organs with dual arterial supply (two arteries supplying them)
List 3 organs with dual arterial supply.
1) lungs - pulmonary arteries and bronchial arteries
2) liver - hepatic arteries and portal vein
3) brain - circle of Willis
Define atherosclerosis.
Formation of atherosclerotic plaques in arteries due to incremental vascular epithelial damage.
Define atherothombosis.
Formation of a thrombus from a spontaneously disrupted atherosclerotic plaque.
Define occlusive thrombosis.
The formation of a thrombus that completely blocks off a blood vessel.
List the 3 main constituents of a plaque.
1) lipids, e.g. cholesterol
2) fibrous tissue
3) inflammatory cells
List the 6 main risk factors for atherosclerosis.
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
List 5 preventative and therapeutic measures for atherosclerosis.
1) smoking cessation
2) weight loss
3) blood pressure control
4) low dose aspirin
5) statins
Where do atherosclerotic plaques tend to form?
Arterial branching points and bifurcations.
List 6 complications of atherosclerosis.
1) carotid atheroma
2) cerebral infarct
3) myocardial infarct
4) aortic aneurysm
5) peripheral vascular disease
6) gangrene
List the 4 stages of an atheroma.
1) fatty streaks
2) intermediate lesion
3) fibrous plaque
4) plaque rupture
What percentage of a vessel wall need to be blocked by an atheroma for symptoms to appear?
50-70% —> critical reduction —> reversible tissue ischaemia.
How is the size of an atheroma estimated?
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.
What is the main constituent of an arterial thrombus?
Platelets —> white thrombus.
What drugs do you prescribe for arterial thrombi?
Anti-platelets.
What is the main constituent of a venous thrombi?
Fibrin (fibrin mesh entrapping RBCs) —> red thrombus.
What drugs do you prescribe for venous thrombi?
Anti-coagulants.
