Thrombosis And Embolism Flashcards

1
Q

What is thrombosis

A

Process leading to formation of thrombus

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2
Q

What is a thrombus

A

Blood clot

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

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3
Q

What are the main constituents of a thrombus

A

Platelets and fibrin

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4
Q

What types of thrombosis are there?

A

Physiological and pathological

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5
Q

When is thrombosis a normal mechanism?

A

Preventing bleeding when a vessel wall is breached

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6
Q

When does thrombosis become pathological

A

When it is not controlled by fibrinolysis

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7
Q

Describe normal thrombosis

A

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

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8
Q

What is fibrinolysis

A

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

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9
Q

What occurs to control the side of the thrombus

A

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

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10
Q

Describe pathological thrombosis

A

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

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11
Q

How does the thrombus grow in pathological thrombus?

A

Accretion of layer upon layer

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

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12
Q

What are D-dimers?

A

Breakdown product of a fibrin mesh, stabilised by factor XIII

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13
Q

What factors predispose thrombus formation?

A
  1. Damage to vessel wall (endothelium)
  2. Stasis (slow or turbulent)
  3. Change in character of blood (increased platelets, RBCs)
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14
Q

Where does pathological thrombosis occur?

A

Arteries
Veins
Heart

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15
Q

Most prominent predisposition factor of arteries?

A

Vessel wall damage

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16
Q

Most prominent predisposition factor of veins?

A

Stasis

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17
Q

Most prominent predisposition factor of the heart?

A

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

18
Q

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

A

Tissue will become ischaemic

Tissue death due to reduced blood flow - infarction

19
Q

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

A

Stays there - swollen leg

Moves - pulmonary embolism

20
Q

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

A

Inflammation, sticky, thrombus forms

Stroke (left ventricle)

21
Q

What woukd white markings be in a heart?

A

Scarring from MI

22
Q

What effect would a thrombus on mitral valve cause?

A

Same as having thrombus in left ventricle

23
Q

What happens to thrombus?

A
Lysed by intrinsic fibrinolysis - rare
Completely block lumen - occlusion
Undergo organisation and recanalisation 
Extend locally - propagation
Fragment or detach and travel elsewhere- thromboembolism
24
Q

What happens when a thrombus occludes a vessel?

A

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

25
Q

What occurs if the thrombus organises and recanalises?

A

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

26
Q

Embolism

A

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

27
Q

Most important materials to embolise

A

Thrombus

Cancer cells

28
Q

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

A

Systemic arterial system

29
Q

What will a blockage of brain arteries cause?

A

Stroke

30
Q

What will blockage of lower limb arteries cause?

A

Gangrene of legs

31
Q

What will blockage of mesenterric arteries cause?

A

Bowel necrosis

32
Q

What will blockage of renal arteries cause

A

Kidney infarct

33
Q

What will blockage of splenic artery cause

A

Splenic infarct

34
Q

Where will a thrombus in a systemic vein embolise to?

A

Pulmonary artery branch - pulmonary embolus

35
Q

Impact of pulmonary embolus on patient

A

Small - small peripheral lung infarct

Large - sudden death

36
Q

Examples of systemic emboli

A

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

37
Q

What is a VTE risk assessment ?

A

Risk assessment for venous thromboembolism

38
Q

How does VTE RA work?

A
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
39
Q

Other materials that are embolised

A

Fat and marrow
Air
Nitrogen
Amniotic fluid

40
Q

D-dimer test

A

Diagnose thrombus presence

If negative for D-dimer, unlikely to have serious venous blood clot

41
Q

What is infarction

A

Special kind of necrosis due to reduced blood flow