Haematology - Venous Thrombosis

Question 1

What makes up Virchow’s Triad?

Answer 1

• Vessel Wall (endothelial injury)
• Blood (hypercoagulability)
• Flow (stasis of blood flow)

Question 2

What is the escalation of investigations based off different Well’s scores?

Answer 2

Low Wells Score:
- Consider other diagnosis

Intermediate Wells Score:
- D-dimer
- IF high = USS/CTPA
- IF low = rule out

High Wells Score:
- USS affected limb for DVT/CTPA for PE

Question 3

What are some inherited causes that increase VTE risk?

Answer 3

• Antithrombin deficiency
• Protein C deficiency
• Protein S deficiency
• Factor V Leiden
• Lupus anticoagulant
• Coagulation Excess

Question 4

What are some acquired causes tht increase VTE risk?

Answer 4

• Age
• Obesity
• Prev. DVT/PE
• Immobilisation
• Major surgery
• Long distance travel
• Malignancy
• Pregnancy, COCP, HRT
• APLS
• Polycythaemia
• Thrombocythaemia

Question 5

What cause is the hgihest risk of a fatal thrombotic event?

Answer 5

Antithrombin deficiency

Question 6

What is the mode of inheritance of protein C/S deficiency, its associations, diagnosis + management?

Answer 6

Autosomal Dominant

• A/w: Warfarin-induced skin necrosis (initial pro-coagulant state)
• Dx: Protein C/S assay

Tx: Long-term anticoagulation with argatroban

Question 7

What are the different indications for warfarin reversal?

Answer 7

• INR <= 5: Lower/omit next dose
• INR 5-9: Omit next dose/Oral Vitamin K
• INR >9: Omit next dose + Oral Vitamin K

Any bleeding = omit next dose + vitamin K + PCC/FFP

Question 8

What is used for DVT prophylaxis?

Answer 8

• Daily SC LMWH (prophylactic dose)
• TED stockings

Question 9

What is the treatment for a DVT/PE?

Answer 9

• LMWH (treatment dose) followed by Warfarin or DOAC (apixaban, rivaroxaban, edoxaban)
• LMWH stopped once INR = 2-3

Question 10

Why is LMWH continued whilst Warfarin is started in DVT/PE Tx?

Answer 10

Warfarin affects Protein C/S + leads to procoagulant sstate in first few days before anticoagulant effect

Question 11

What is the minimum treatment duration for VTE?

Answer 11

3 months

Question 12

What is the action of heparin?

Answer 12

Potentiates antithrombin III which inactivates thrombin + Fx IX, X, XII

Question 13

When is LMWH given + its monitoring requirements?

Answer 13

• SC once daily
• No monitoring (excep tin late pregnancy, renal failure&raquo_space; monitor anti-Xa levels)

Question 14

When is unfractionated heparin given + its monitoring requirements?

Answer 14

IF renal impairment
- IV loading dose then infusion
- Monitor APTT (or anti-Xa/heparin levels)

Question 15

What is given to reverse the effects of heparin?

Answer 15

Protamine sulphate

Question 16

What are some side effects of heparin?

Answer 16

• Bleeding
• Heparin-induced thrombocytopenia
• Osteoporosis (with long-term use)

Question 17

What is the mechanism of action of warfarin?

Answer 17

Inhibits reductase enzyme responsible for regenerating the active form of vitamin K so inhibits the synthesis of Factors II, VII, IX, X + proteins C, S + Z

Question 18

What is given to reverse the effects of warfarin?

Answer 18

• IV Vitamin K (6hrs)
• Prothrombin complec concentrate (30mins)

Question 19

What are some risks associated with Warfarin?

Answer 19

Teratogenicity

Question 20

What are the target INRs and which indications do they have?

Answer 20

• 2.5: 1st episode DVT/PE atrial fibrillation (2-3)
• 3.5: Recurrent DVT/PE, mechanical prosthetic valve (2.5-3.5)

Question 21

What are some pros of DOACs?

Answer 21

• Oral
• Immediate effects (peak 3-4hrs)
• Short half-life (~12hrs) = useful longterm = no monitoring

Question 22

What are the suffixes for DOACs mechanisms of action?

Answer 22

-oxaban: Anti- Xa
-gatran: Anti-IIa