Cardiovascular: Haemostasis (Clotting)

Question 1

Describe 5 broard stages of the formation of a platelet-fibrin clot

Answer 1

First 3 are the formation of the platelet rich thrombus:

1. Platelet adhesion
2. Platelet activation
3. Platelet aggregation

The next 2 are the stabilisation with fibrin:

4. Conversion of fibrinogen to fibrin by thrombin
5. Finally the polymerisation of fibrin resulting in a stable platelet-fibrin clot ( aslo known as a white clot)

Question 3

What does thrombin do?

Answer 3

Converts fibrinogen into fibrin

Question 4

Difference between aggregation and coagulation?

Answer 4

Aggregation - platelets
Coagulation - fibrin

Question 5

Which parts of the clotting process do aspirin and warfarin act on?

Answer 5

• Aspirin - platelet aggregation
• Warfarin - coagulation

Question 6

Detailed action of warfarin vs DOACs

Answer 6

By blocking the conversion of inactive vitamin k to active vitamin k warfarin takes serval days to work and also block the creation of protein C which is a natural anticoagulant.

DOACs directly block clotting factor X therefore acting much fasting without inhibiting protein C.

Question 7

Why can warfarin actually temporarily increase clotting?

Answer 7

The factors that warfarin inhibits that making of hang around in stock piles for a while whereas protein C doesn’t. So before the clotting factors are fully blocked you actually inhibit the anti-coagulant effect of protein C first thus temporarily increasing coagulation.

Question 8

Three natural coagulation inhibitors

Answer 8

Tissue factor pathway inhbitor
Antithrombin
Protein C

Question 9

Which clotting factor is difficient in haemophilia a?

Answer 9

fVIII

Question 10

Which clotting factor is difficient in haemophilia b?

Answer 10

IX

Question 11

What is Von Willebrand Disease?

Answer 11

A lack of Von Willebrand Factor

Von Willebrand Factor helps platelet adhersion to subendothelium and also is a carrier molecule for fVIII so lacking this leads to low level of VIII

Question 12

Order of rarity out of haemophilia A, B and vWB disease

Answer 12

Most rare

1. Haemophilia B
2. Haemophilia A
3. Von Willebrand disease

Most common

Question 13

Common aquired coagulation disorders

Answer 13

• Vit K deficiency
• Liver failure (liver makes many coagulation factors)
• Immune (aquired haemophilia of vWB disease)
• Anticoagulants
• Consumption of coagulation factors

Question 14

What is DIC

Answer 14

Disseminated Intravascular Coagulation

It is an explosion of thrombin

Leads to widespread deposition of circulating fibrin leading to widespread ischemia

Consumption of platelets and clotting factors to make thrombin can lead to sever bleeding

Can be causes by anything systemically traumatic such as sever sepsis or metastatic cancer