Thrombosis And Embolism

Question 1

What is thrombosis

Answer 1

Process leading to formation of thrombus

Question 2

What is a thrombus

Answer 2

Blood clot

Solid mass made of blood constituents which have aggregated together in flowing blood of the lumen of a blood vessel

Question 3

What are the main constituents of a thrombus

Answer 3

Platelets and fibrin

Question 4

What types of thrombosis are there?

Answer 4

Physiological and pathological

Question 5

When is thrombosis a normal mechanism?

Answer 5

Preventing bleeding when a vessel wall is breached

Question 6

When does thrombosis become pathological

Answer 6

When it is not controlled by fibrinolysis

Question 7

Describe normal thrombosis

Answer 7

Vessel wall breached
Circulating platelets aggregate to plug gap
Platelets release factors which trigger cascade
Cascade converts fibrinogen to fibrin
Fibrin bind together platelets and entrap WBCs and RBCs

Question 8

What is fibrinolysis

Answer 8

Breaking down of fibrin so the thrombus dissolves
Plasmin is the enzyme
Broken down products are the fibrin degradation products

Question 9

What occurs to control the side of the thrombus

Answer 9

Plasminogen converted to plasmin by plasminogen activator (tissue plasminogen activator)
Plasminogen and t-PA bund to fibrin
t-PA converts nearby plasminogen to plasmin which begins to degrade the fibrin

Question 10

Describe pathological thrombosis

Answer 10

Occurs when thrombus enlarges beyond vessel healing requirements and continues to grow
Beyond certain thrombus size and rate of development, intrinsic fibrinolytic system is incapable of controlling size of thrombus

Question 11

How does the thrombus grow in pathological thrombus?

Answer 11

Accretion of layer upon layer

If it continues unrestrained, reddish-brown mass is produced in vessel

Question 12

What are D-dimers?

Answer 12

Breakdown product of a fibrin mesh, stabilised by factor XIII

Question 13

What factors predispose thrombus formation?

Answer 13

1. Damage to vessel wall (endothelium)
2. Stasis (slow or turbulent)
3. Change in character of blood (increased platelets, RBCs)

Question 14

Where does pathological thrombosis occur?

Answer 14

Arteries
Veins
Heart

Question 15

Most prominent predisposition factor of arteries?

Answer 15

Vessel wall damage

Question 16

Most prominent predisposition factor of veins?

Answer 16

Stasis

Question 17

Most prominent predisposition factor of the heart?

Answer 17

Ventricles - chamber wall damage
Atrium - stasis
Heart valves - valve surface damage

Question 18

What effect will a thrombus forming an atheroma in a coronary artery?

Answer 18

Tissue will become ischaemic

Tissue death due to reduced blood flow - infarction

Question 19

What effect will a thrombus formed in a vein in a leg cause?

Answer 19

Stays there - swollen leg

Moves - pulmonary embolism

Question 20

What effect will a thrombus formed in a heart chamber cause?

Answer 20

Inflammation, sticky, thrombus forms

Stroke (left ventricle)

Question 21

What woukd white markings be in a heart?

Answer 21

Scarring from MI

Question 22

What effect would a thrombus on mitral valve cause?

Answer 22

Same as having thrombus in left ventricle

Question 23

What happens to thrombus?

Answer 23

Lysed by intrinsic fibrinolysis - rare
Completely block lumen - occlusion
Undergo organisation and recanalisation 
Extend locally - propagation
Fragment or detach and travel elsewhere- thromboembolism

Question 24

What happens when a thrombus occludes a vessel?

Answer 24

Artery - stops flow of blood, cuts off oxygen to issue - infarction
Vein - prevents venous drainage of tissues, blood pools - congestion and infarction (often haemorrhagic)

Question 25

What occurs if the thrombus organises and recanalises?

Answer 25

New vessels grow into thrombus Vascular granulation tissue develops Fibroblasts invade and deposit collagen Fibrovascular granulation tissue develops

Question 26

Embolism

Answer 26

Transference is abnormal material by blood stream with eventual impact action of the material in a vessel distal to origin

Question 27

Most important materials to embolise

Answer 27

Thrombus | Cancer cells

Question 28

Where does a thrombus in an artery or left side of the heart embolise to?

Answer 28

Systemic arterial system

Question 29

What will a blockage of brain arteries cause?

Answer 29

Stroke

Question 30

What will blockage of lower limb arteries cause?

Answer 30

Gangrene of legs

Question 31

What will blockage of mesenterric arteries cause?

Answer 31

Bowel necrosis

Question 32

What will blockage of renal arteries cause

Answer 32

Kidney infarct

Question 33

What will blockage of splenic artery cause

Answer 33

Splenic infarct

Question 34

Where will a thrombus in a systemic vein embolise to?

Answer 34

Pulmonary artery branch - pulmonary embolus

Question 35

Impact of pulmonary embolus on patient

Answer 35

Small - small peripheral lung infarct | Large - sudden death

Question 36

Examples of systemic emboli

Answer 36

Thrombus in mitral valve - tissue necrosis in kidney Left ventricular wall - brain, secondary haemorrhage Calf - pulmonary embolism

Question 37

What is a VTE risk assessment ?

Answer 37

Risk assessment for venous thromboembolism

Question 38

How does VTE RA work?

Answer 38

``` Active cancer treatment/cancer Age >60 Dehydration Known Obesity One or more significant medical Personal or first degree relative Hormone replacement therapy Oestrogen containing contraceptive Varicose veins with phlebitis Pregnancy ```

Question 39

Other materials that are embolised

Answer 39

Fat and marrow Air Nitrogen Amniotic fluid

Question 40

D-dimer test

Answer 40

Diagnose thrombus presence | If negative for D-dimer, unlikely to have serious venous blood clot

Question 41

What is infarction

Answer 41

Special kind of necrosis due to reduced blood flow