Thrombosis and embolism

Question 1

What is a thrombus?

Answer 1

An aggregate of coagulated blood/ a stationary mass containing platelets, fibrin, and RBC’s in flowing blood

Question 2

Causes of endothelial damage in arteries?

Answer 2

1. Atherosclerotic plaque
2. Vasculitis
3. Turbulent flow / Hypertension=> Haemodynamic stress
4. Cigarette smoke

Question 3

Causes of abnormal blood flow in arteries and veins?

Answer 3

1. Arteries
   - Turbulent => Because of fast, high pressure flow
2. Veins
   - Stasis=> Because slower, low pressure flow

Question 4

Causes of hypercoagubility?

Answer 4

1. Primary (Genetic)
   - Mutation in factor V gene
   - Mutation in prothrombin gene
   - Antithrombin III deficiency
   - Protein C and S deficiency
2. Secondary (Acquired)
   - Tissue damage (burns, surgery, fracture)
   - Cancer
   - Pregnancy (and other hyperestrogenic states)
   - DIC
   - COCP
   - APAS
   - Nephrotic syndrome
   - Polycythaemia

Question 5

Causes of thrombosis in arteries and veins?

Answer 5

1. Arteries
   - Atherosclerotic plaques
   - Stasis
   - Turbulence
   - Hypertension
   - Counter currents
2. Veins
   - Stasis
   - Hypercoagubility

Question 6

Clinical effects of arterial thrombosis?

Answer 6

1. Ischaemia and infarction
   - MI
   - CI
   - Acute limb ischaemia
2. Embolus (which also causes infarct) into other arteries or arterioles
   - Brain, Kidney, Spleen

Tend to form systemic emboli

Question 7

Clinical effects of venous thrombosis?

Answer 7

1. Oedema and pain
2. May have necrosis and gangrene
3. PE
4. Embolisation to venous sinuses of skull (less common)

Question 8

When and where may we find Heart Thrombi?

Answer 8

1. Mural thrombus (on endocardium) post MI
2. Thrombi on cardiac valves in infective endocarditis
3. In left atrium, esp auricular appendix, in atrial fibrillation

Tend to from systemic emboli

Question 9

What is an embolus?

Answer 9

Detached intravascular mass that travels from one part of the circulation to another.
Can be pulmonary or systemic

Question 10

Examples of emboli?

Answer 10

1. Detached thrombi
2. Septic
3. Air or gas
4. Fat
5. Amniotic fluid
6. Foreign bodies
7. Tumours

Question 11

Pulmonary emboli features?

Answer 11

1. Usually from deep veins of lower limbs. Sometimes from right side of heart
2. Massive, Intermediate, Micro emboli
3. Paradoxical emboli (rare)
4. Diagnose by checking D Dimers and doing a CT Pulmonary Angiogram

Question 12

Systemic emboli features?

Answer 12

1. Usually from left side of heart, aorta, or carotids

2. Lodge anywhere in systemic circ.

Question 13

Air/gas emboli features?

Answer 13

1. Occurs due to damage of veins in head and neck

2. or due to decompression sickness

Question 14

Fat embolism features?

Answer 14

1. Tiny globules of fat get into circ. when long bones fractured, so vessels in marrow torn, so fat leaks.
2. Dyspnoea, cyanosis, mental confusion, unconsciousness, convulsion, petechial haemorrhages around neck and chest.

Question 15

What is the function of normal endothelial cells in regards to thrombi formation and what do they secrete to achieve this?

Answer 15

Normal endothelial cells reduce thrombi formation, inhibit coagulation and encourage fibrinolysis.

They do this by secreting prostacyclin, thrombomodulin, plasminogen activator and NO.

Question 16

What do damaged endothelial cells secrete that make them prothrombotic?

Answer 16

Platelet aggregating factor, platelets which produce thromboxane, and plasminogen activator inhibitors.

Question 17

Potential fates of a thrombus?

Answer 17

1. Propagation
2. Embolus
3. Dissolution
4. Organisation and recanalisation of the blood vessels.

Question 18

What is a paradoxical embolism?

Answer 18

A rare event where an embolus may pass through an interatrial or interventricular defect to gain access to the systemic circulation.