Thrombosis

Question 1

What makes up Virchow’s triad?

Answer 1

Endothelial damage
Abnormal blood flow
Hypercoaguability

Question 2

Damage to the endothelium exposes which receptors?

Answer 2

collagen and vWF receptors which platelets can bind to!

Question 3

Name some states of hypercoaguability

Answer 3

After surgery, trauma, moderate/severe inflammation, T2DM

Pregnancy + some OC raise protein S concentrations –> predisposing to hypercoaguability

Question 4

For how long are coagulation factors raised after surgery?

Answer 4

Several weeks, or severe surgery e.g. hip surgery can have DVT risk for 3 months!

Question 5

Acquired thrombophilias

Answer 5

• Atherosclerosis
• Pregnancy/oestrogens
• Diabetes
• ANTIBODIES: antiphospholipid antibodies, heparin-induced antibodies

Question 6

What is antiphospholipid antibody syndrome?

Answer 6

Recurrent thrombosis, pregnancy loss due to antibodies for the the phospholipid component of platelets, activates them

Question 7

What is heparin-induced antibody?

Answer 7

Treatment >5 days with heparin, causes platelet activation in the presence of heparin

Question 8

How is nephrotic syndrome a thrombosis risk?

Answer 8

Loss of antithrombin across the glomerulus

Question 9

What is the main cause of thrombi in arteries compared to veins?

Answer 9

Artery - endothelial injury + altered blood flow

Venous - altered blood flow and changes in coagulation

Question 10

What is factor V Leiden?

Answer 10

Mutation in factor 5, mild predisposition to thrombosis

Question 11

Deficiency of what could lead to thrombosis?

Answer 11

Antithrombin, protein C or S

Question 12

What lab tests to do in DVT?

Answer 12

Full blood screen: look for raised Hb, platelets, leakeaumias
APTT, PT, fibrinogen tests
D-dimer

Specialist tests: factor V leiden, concentrations of inhibitors etc

Question 13

Why is lupus a thrombosis risk?

Answer 13

Often have antiphospholipid antibodies which activate platelets

Question 14

Whats is the Well’s score?

Answer 14

DVT risk score

1) cancer
2) immobilisation
3) bed rest >3 days/major surgery past 12 weeks
4) past DVT

5) localised tenderness
6) swelling entire leg
7) calf swelling >3cm
8) pitting oedema
9) collateral superficial veins

10) other diagnosis at least as likely

> 3 high prob

0 low

Question 15

What is the difference between unfractionated heparin and LMWH (clexane)?

Answer 15

Both IV or subcut

Unfractionated only used very short term due to cost + heparin-antibody risk. e.g. during surgery

LMWH is for prophylaxis, reduced antithrombin effect compared to UFH (lower beleding risk), maintains factor X effect

Question 16

Why must we use bridging therapy for warfarin?

Answer 16

When you start warfarin, C+S are rapidly reduced, these are INHIBITORS of thrombosis, and as such there is actually an increased thrombosis risk at the beginning. Have to use heparin for 5-10 days.

Question 17

Dabigatrin vs rivaroxaban

Answer 17

Dabi - direct anti-thrombin
Rivaroxaban - direct anti-Xa

Question 18

INR targets

Answer 18

2-2.5 for DVT prophylaxis
2-3 for treatment of DVT, PE, AF, TIA
3-4.5 for recurrent above + some prosthtic valve replacements