Thrombosis

Question 1

What is virchows triad?

Answer 1

describes the three broad categories of factors that are thought to contribute to thrombosis.

1. Vessel injury
2. Venous stasis
3. Hypercoagulability

Question 2

Purpose of clotting cascade?

Answer 2

Make thrombin so fibrinigen can be converted to fibrin

Fibrin forms strands which solidifies the agglutinated platelets to prevent blood loss.

Question 3

Types of thrombosis?

Answer 3

Arterial and venous

Question 4

Arterial thrombosis cause and effects?

Answer 4

• Rupture from atheroma or damage to endothelium (MI, stroke)
• Platelet rich “white” thrombosis
• May block downstream arteries

Question 5

Venous thrombosis causes and effects?

Answer 5

• Often from stasis or hyper-coagulant state
• Platelet poor “red” thrombus
• May move to lungs

Question 6

Why are veins often sites of thrombosis?

Answer 6

Blood tends to eddy around valves increasing risk of stasis

Damaged valves may cause backflow of blood - so blood pools in legs

Question 7

4 fates for thrombus

Answer 7

• Resolution (thrombolysis)
• Embolism
• Organised (covered by endothelium)
• Recanalised and organised

Question 8

Two types of DVT?

Answer 8

Proximal (higher risk of pulmonary embolism + post-thrombotic syndrome)

Distal (rarely causes embolism and syndrome)

Question 9

what is post thrombotic syndrome?

Answer 9

Inflammation along with damage to the venous valves from the thrombus itself.

Question 10

Two pathways for clotting cascade?

Answer 10

Extrinsic and intrinsic

Question 11

Purpose of clotting cascade?

Answer 11

Produce activated Xa (protease) which catalyses prothrombin (II) to thrombin (IIa)

Thrombin cleaves fibrinogen into fibrin

Question 12

What is antithrombin?

Answer 12

small protein molecule made by the liver that circulates in the plasma.

Question 13

How is antithrombin activated?

Answer 13

Heperan is expressed by endothelial cells
Binds to enzyme inhibitor antithrombin III causing a conformational change