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Pathology > arterial and venous thrombosis > Flashcards

arterial and venous thrombosis Flashcards

1
Q

Why don’t blood clots form all the time?

A 
reasons from lecture:
1. laminar flow - cells travel un the centre of a vessel and don't come into contact with the walls 
2. endothelial cells are not sticky when healthy 
reasons from last year
endothelial cells,
anticoagulant pathway and
fibrinolytic pathway keep it fluid
platelets and coagulation proteins
circulate in an inactive form
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2
Q

what is the definition of thrombosis?

A

solid mass of blood constituents formed within intact vascular system during life

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3
Q

What are the components of Virchow’s triad?

A
  1. change in vessel wall
  2. change in blood flow
  3. change in blood constituents
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4
Q

What is the first stage of thrombosis?

A

platelet aggregation

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5
Q

What type of feedback does thrombosis involve?

A

positive feedback

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6
Q

What protein is formed as a product of the clotting cascade?

A

fibrin

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7
Q

Which cascade does platelet activation trigger?

A

coagulation cascade

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8
Q

Referring to Virchow’s triad, what does smoking cause?

A

change in vessel wall

change in blood flow (over the injured/absent cells)

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9
Q

What interventions in hospital can reduce risk of thrombosis?

A

early mobilisation after operation
low dose subcutaneous heparin
venous stockings

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10
Q

According to Virchow’s triad, what is venous thrombosis due to?

A

change in blood flow (stasis of blood)

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11
Q

How does aspirin work?

A

Inhibits platelet aggregation - antiplatelet drug, irreversibly inhibtis COX to reduce production of pro-aggregatory factor thromboxane from arachidonic acid.

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12
Q

What is an embolus?

A

mass of material in the vascular system able to become lodges within a vessel and block it

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13
Q

How does a DVT embolise?

A

The distal part of the thrombus breaks off and travels to the vena cava, then right side of the heart and then to the lungs - pulmonary arteries

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14
Q

What are the other types of embolism other than that from thrombosis?

A

air (pressurised systems of IV fluids/blood in infants and children)
cholesterol crystals (from an atheromatous plaque)
tumour
amniotic fluid (may happen in women with precipitate labour - i.e. very fast labour)
fat (severe trauma with multiple fractures)

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15
Q

Where do arterial thrombi embolise to?

A

if the thrombus is in the heart, the embolus can travel anywhere in the systemic circulation e.g. lower limb and renal arteries

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16
Q

Give examples of complications of arterial thrombi

A

stroke

heart attack

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17
Q

Give an example of complication of a venous thrombus

A

PE

18
Q

How does thrombosis occur on top of an atheroma?

A

The plaque ruptures, exposing collagen, leading to platelet aggregation and activation of the clotting cascade

19
Q

Why is oedema seen with venous thrombosis?

A

impaired venous drainage

20
Q

What do alpha granules contain?

A

substances involved in platelet adhesion such as fibrinogen, fibrognectin, platelet derived growth factor

21
Q

What do dense granules contain?

A

ADP

22
Q

Name two factors that cause platelets to degranulate when they come into contact with the substance?

A

fibrin

collagen

23
Q

Describe the steps of arterial thrombosis

A
  1. turbulent flow (e.g. caused by endothelial damage or a plaque)
  2. leads to loss of endothelial cells
  3. exposure of underlying collagen
  4. platelet activation
  5. fibrin deposition
  6. RBCs trapped
  7. alternating layers of platelets and RBCs in fibrin mesh
24
Q

Describe the steps of venous thrombosis

A
  1. low blood pressure in veins
  2. valves produce turbulence
  3. thrombi form due to endothelial damage, exposure of collagen, activation of platelets, fibrin formation, trapping of RBCs

in lec - if BP drops, then cells settle to the bottom of a vessel, so no longer laminar flow

25
Q

What can cause BP drop in venous circulation?

A

blood loss
anaesthesia
following MI

26
Q

State 5 causes of thrombi in the heart

A
  1. atheromatous plaque
  2. valve vegetation
  3. atrial thrombus (AF)
  4. old myocardial infarct (adynamic part of myocardium)
  5. recent myocardial infarct (fibrosis)
27
Q

Why does vegetation in the heart cause emboli?

A

infective endocarditis
the vegetations are very friable (crumbly)
and contain bacteria

28
Q

How do the lungs act as a filter for emboli?

A

The vessels become very small –> capillaries only allowing one RBC at a time

29
Q

What are the clinical signs of arterial thrombosis?

A
  1. loss of pulse distal to thrombus
  2. cold, pale area (blood is prevented form entering the area)
  3. very painful
    tissue dies –> gangrene
30
Q

What are the clinical signs of venous thrombi?

A
  1. tender, due to ischaemia
  2. swollen
  3. red - blood is still carried to the site, but cannot be drained by veins)
31
Q

Name 4 effects of thrombi

A

lyres and resolution
organisation
recanalisation
embolism

32
Q

What happens in lysis and resolution of thrombi?

A

complete resolution, as the thrombus is small

depends on fibrinolytic activity i.e. plasmin

33
Q

What happened in organisation of thrombi?

A

thrombus is replaced by scar tissue
scar tissue contracts and occludes the lumen
scar tissue formed by invasion of macrophages that clear up the thrombus Fibroblasts replace the thrombus with collagen

34
Q

What happens in recanalisation of thrombi?

A

ingrowth of new vessels, which join up to restore blood flow
the intimal cells proliferate and capillaries grow into the thrombus and fuse to form large vessels
the vessel becomes patent again

35
Q

What are symptoms of PE?

A

chest pain

SOB (loss of lung area supplied by vessel)

36
Q

Name two types of therapy fro PE

A

symptomatic

thromolytic

37
Q

Name two types of therapy fro PE

A

symptomatic

thrombolytic

38
Q

Which vessel can a thrombus in the gut occlude and what are the consequences?

A

superior mesenteric artery SMA
can cause death of whole sections of small bowel
this can lead to peritonitis and death due to perforation

39
Q

Give reasons for a fat embolism

A

fracture of long bones
extensive softy tissue injury
severe burns

40
Q

Give reasons for gas embolism

A

decompression sickness

vessel opened to the air in surgery

Pathology (11 decks)

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