Thrombosis and Embolism Flashcards

1
Q

Thrombosis

A

The process leading to thrombus formation

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2
Q

Thrombus’ main constituents

A

Platelets and fibrin

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3
Q

When can thrombosis be physiological

A

To prevent bleeding when a vessel wall is breached

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4
Q

What process limits physiological thrombosis and how relate to pathological thrombosis

A

Fibrinolysis

Thrombosis becomes pathological when it is not controlled by fibrinolysis

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5
Q

What holds a thrombus together

A

Fibrin

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6
Q

Describe the process of physiological thrombosis

A

Vessel wall is breached and so circulating platelets aggregate to plug the gap

Platelets release factors which trigger coagulation cascade which converts fibrinogen into insoluble fibrin that wraps together platelets and entrapped RBCs and WBCs

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7
Q

Plasmin

A

Active enzyme that fragments/degrades fibrin and thus blood clots

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8
Q

Fibrin degradation products (FDPs)

A

Fragmented bits of fibrin after degradation

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9
Q

Describe the process of normal finrinolysis

A

Inactive plasminogen in plasma becomes plasmin via plasminogen activators (specifically tissue plasminogen activator t-PA)

When fibrin is formed, plasminogen and t-PA bind to it; t-PA activates nearby plasminogen, leading to fibrin degradation

This controls thrombus size

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10
Q

How might pathological thrombosis occur (simple)

A

Thrombus grows beyond vessel healing requirements and continues to grow to a size and rate beyond which the fibrolytic system is incapable of controlling the size

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11
Q

D-Dimers and D-Dimer test

A

D-Dimers are a breakdown product of fibrin mesh, stabilised by factor XIII;

Increased levels may indicate thrombotic events

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12
Q

Factors that predispose thrombus formation (Virchow’s Triad)

A

Damage to vessel wall (especially endothelium)

Stasis of blood

Change in blood character (especially increases in platelets, RBCs and viscosity)

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13
Q

How is arterial thrombosis most likely to occur

A

Main predisposing factor is vessel wall damage

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14
Q

How is venous thrombosis most likely to occur

A

Stasis is the most important factor

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15
Q

How is thrombosis of the heart most likely to occur in the ventricles

A

Chamber wall damage is the most important factor here

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16
Q

How is thrombosis of the heart most likely to occur in the atria

A

Stasis of blood is the most important factor

17
Q

How is thrombosis of the heart valves most likely to occur

A

Valve surface damage is the most important factor

18
Q

What may happen to a thrombus in pathological thrombosis

A

It may be lysed via fibrinolysis (rare)

Occlude the lumen

Extending locally

May undergo organisation & recanalisation

Fragment and detach completely, traveling elsewhere and becoming a thrombo-embolism

19
Q

What does thrombotic occlusion cause in an artery

A

This cuts off blood flow and can cause an infarction

20
Q

What does thrombotic occlusion cause in a vein

A

It prevents venous drainage of tissues, blood pools that cannot escape –> congestion and often haemorrhagic infarctions

21
Q

Recanalisation

A

Re-establishment of blood flow into a formerly occluded region

22
Q

Organisation & Recanalisation of Thrombus

A

New vessels grow into the thrombus, vascular granulation tissue develops

Fibroblasts invade and deposit collagen and so fibrovascular granulation tissue develops

This is an organised thrombus; when vessels link up, some degree of recanalisation may occur

23
Q

Granulation tissue

A

New connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process

24
Q

Embolism

A

Transference of abnormal material by blood stream with eventual impaction of material in a vessel distal to origin

25
Q

Most notable embolised materials

A

Thrombuses and cancer cells (metastasis)

26
Q

Thromboembolism

A

A thrombus breaks off and passes into blood stream to a distal site where they impact and occlude a distal vessel

27
Q

What would a thromboembolism of lower limb arteries cause

A

Gangrene of legs

think ischaemia

28
Q

What might a thrombus in a systemic vein cause

A

This is likely to embolise to a pulmonary artery branch and cause a pulmonary embolus (economy class syndrome)

29
Q

Venous Thromboembolism Risk Assessments

A

Be vaguely aware

30
Q

Some important risk factors of VTE

A
Active cancer/cancer treatment
Age ?60
Dehydration
Obesity
Significant medical comorbidities (e.g. heart disease)
Personal/Close family history
HRT
Contraceptives
Pregnancy/Post partum
31
Q

Other materials that can cause embolism

A

Fat/Marrow
Air
Nitrogen (Decompression sickness)
Amniotic Fluid