CSIM 1.60: Case 46 Launch - A Disastrous Journey Overseas

Question 1

What is the definition of thrombosis? How does this differ from a clot?

Answer 1

Thrombosis is a solid mass of blood constituents formed within blood vessels in life.

A clot, however, can occur inside or outside of the vascular system in life or post mortem, and simply refers to coagulation

Question 2

Describe the composition of thrombi

Answer 2

• Fibrin polymer
  
  • Platelets
  • Entrapped RBCs and serum

Question 3

Describe the contents of platelets

Answer 3

• Alpha granules
  
  • Dense granules
  • No nucleus

Question 4

What are platelets derived from?

Answer 4

Megakaryocytes

Question 5

What is the role of:
1) Alpha granules
2) Dense granules
(FROM PLATELETS)

Answer 5

1) Adhesion

2) Aggregation

Question 6

Describe what platelets do when they come into contact with fibrin or collagen

Answer 6

Release granules promoting aggregation of adjacent platelets to form a mass

Question 7

What three factors promote thrombosis?

What is this known as?

Answer 7

• Endothelial/wall damage
  
  • Abnormal blood flow
  • Hypercoagubility

Virchow’s triad

Question 8

Describe normal blood flow. What is this called?

When does this go wrong?

Answer 8

LAMINAR FLOW:
• RBCs, WBCs and platelets travel axially
• Plasma travels marginally

During times of stagnation (e.g. due to wall lesions such as atheroma) this laminar flow can become disrupted, causing ‘TURBULENT FLOW’ (IMG 147)

Question 9

What are the types of hypercoagubility states?

Answer 9

Primary hypercoagubility
• Genetic

Secondary hypercoagubility
• Acquired
• E.g. immobilisation, MI, tissue damage, neoplasia, AF, smoking, etc.

Question 10

What are the three types of thrombi?

Answer 10

Occlusive thrombi
• Occlude the vessel
• Causes infarction

Mural thrombi
• On the side of vessel
• Release emboli

Vegetation thrombi
• On heart valves, often due to infection
• Release emboli

IMG 148

Question 11

What are the four final outcomes of thrombosis?

Answer 11

Thrombolysis
• Cleared by the fibrinolytic system
• Endothelial cells release plasminogen factor
• This converts plasminogen into plasmin
• Plasmin dissolves fibrin

Recanalisation
• Endothelial cells grow out from the vessel wall
• These then create new channels through the thrombus

Embolism
• Thrombosis throws off emboli

Fibrosis organisation
• Thrombosis can undergo fibrous tissue replacement

Question 12

Describe the role of thrombin?

Answer 12

Prothrombin is converted into thrombin, which converts fibrinogen into fibrin

Question 13

What can cause blood turbulence in the heart?

What can cause endothelial damage in the heart?

What can cause vegetations on the heart valves?

Answer 13

AF

MI

Bacterial endocarditis

Question 14

What increases the risk of venous thrombosis?

How is this minimised?

Answer 14

• Immobility (slow blood flow)
  
  • Operations (fibrinogen + coagulation factors increased due to hepatic synthesis)
  • Surgical damage to endothelium in calf veins

Heparin given post-surgery

Question 15

Where does venous thrombosis most commonly occur?

Answer 15

Deep veins

Question 16

What is the definition of an embolus?

Answer 16

A mass of material in the blood which can lodge in a vessel to occlude it

Question 17

Other than a thrombus, what are the types of emboli?

Answer 17

• Atheroma
  
  • Fat
  • Infective vegetations
  • Gas
  • Amniotic fluid (foetal cells, hair, etc.)
  • Tumour
  • Foreign matter

Question 18

What are the origins and destinations of venous and arterial emboli?

Answer 18

Venous emboli:
• Deep veins origin
• Travels to pulmonary arteries

Arterial emboli:
• Heart or large arteries origin
• Travels to organs and systemic circulation

Question 19

Where does DVT most commonly develop?

Answer 19

Calf or ileofemoral veins

Question 20

What is a rarer source of pulmonary thromboemboli?

Answer 20

Right atrium mural thrombus in atrial fibrillation

Question 21

What do the effects of pulmonary emboli depend on?

Answer 21

Size:
• Large, 5% = sudden death, usually saddle embolus
• Medium, 10% = clinically evident, occlusion of a branch of bulmonary artery causing a pulmonary infarction
• Small, 85% = clinically silent, however many lead to pulmonary hypertension

Question 22

What is a saddle embolus?

Answer 22

A long embolus which ‘sits’ on the septum at the point where arteries in the lung bifurcate

Question 23

What is the cause and symptoms of a pulmonary infarct?

Answer 23

Medium PE
• Pleuritic chest pain
• Haemoptysis

Question 24

Why do small pulmonary emboli usually not cause symptoms?

What conditions can accumulation of these lead to?

Answer 24

Areas of lung supplied by smaller arteries usually have collateral blood supply

• Pulmonary hypertension
• Cor pulmonale

Question 25

What are the four main sources for systemic (arterial) emboli?

What is the main CAUSE for each of these sources?

Answer 25

Arteries 
  •  Atheroma
Valves (left)
  •  Infection
Endocardium (myocardium)
  •  Infarct 
Left atrium 
  •  Fibrillation

IMG 151

Question 26

What are the typical effects of systemic emboli which end up in the foot?

Answer 26

Gangrene