Thrombosis

Question 1

Define thrombus.

Answer 1

Abnormal coagulum formed within the circulation from the flowing constituents of the circulation.

Question 2

What is Virchow’s triad?

Answer 2

Endothelial injury, turbulent blood flow, hypercoagulable blood.

Question 3

Describe the process of platelet activation and aggregation.

Answer 3

1. When endothelium is lost underlying collagen exposed.
2. Collagen + con Willebrand’s factor (vWF) binds to glycoprotein Ia/IIb on platelets.
3. Increase in platelet integrins.
4. Glycoprotein IIb/IIIa binds fibrinogen.
5. Activated platelets release granules to attract other platelets (vWF, platelet activating factor (PAF), thromboxane A2 (TXA2), ADP).

Question 4

What is the intrinsic pathway of the coagulation cascade measured by?

Answer 4

Prothrombin time (PT).

Question 5

What is the extrinsic pathway of the coagulation cascade measured by?

Answer 5

Activated partial thomboplastin time (APTT).

Question 6

What factors is vitamin K required to make?

Answer 6

II, VII, IX and X.

Question 7

What is vitamin K soluble in and where is it stored?

Answer 7

Fat, stored in the liver.

Question 8

What 2 things can stop production of factors II, VII, IX and X?

Answer 8

Liver disease and warfarin.

Question 9

What needs to be present in the arterial system for thrombosis to occur?

Answer 9

Atherosclerosis.

Question 10

Where are the common sites for atherosclerosis?

Answer 10

Cerebral vessels, carotid arteries, coronary arteries, aorta.

Question 11

What are some causes of endothelial injury?

Answer 11

Hypertension, toxins e.g. smoking, infectious agents, smoking related. Rare: primary vasculitis (autoimmune disease characterised by inflammation directed at vessel walls).

Question 12

Why does stasis increase coagulation?

Answer 12

Increased contact of platelets etc with vessel wall and no washing out.

Question 13

What can cause stasis in the deep venous system?

Answer 13

Faulty valves and venous insufficiency.

Question 14

Name some causes of hypercoagulability.

Answer 14

Anything causing increased viscosity: dehydration, polycythaemia (increased cell number), leukaemias.

Question 15

What is marantic endocarditis?

Answer 15

Aseptic thrombotic endocarditis.

Question 16

What types of drugs can increase risk of thrombosis?

Answer 16

Chemotherapeutic agents (injure endothelium and increase risk of thrombosis).

Question 17

Name an autoimmune disease that can cause thrombosis?

Answer 17

Antiphospholipid syndrome.

Question 18

What mutation can cause hypercoagulability and how?

Answer 18

Factor V Leiden, anticoagulant proteins can’t bind to it so it starts the coagulation cascade.

Question 19

What deficiencies can cause hypercoagulability?

Answer 19

Protein C, protein S, antithrombin III.

Question 20

Name 3 anticlotting proteins.

Answer 20

Protein C, protein S (degrade factor V and VIII), antithrombin III (degrades II, IX and X).

Question 21

Name the other kinds of embolus.

Answer 21

Air, septic, amniotic fluid, tumour (renal cell carcinoma, liver cancer), fat (after massive trauma, fat from bone marrow).

Question 22

What are the known consequences of venous thromboembolism?

Answer 22

Fatal PE, risk of recurrent VTE, post-thrombitc syndrome (PTS), chronic thromboembolic pulmonary hypertension (CTEPH), reduced quality of life.

Question 23

What are the symptoms of post-thrombotic syndrome?

Answer 23

Pain, oedema, hyperpigmentation, eczema, varicose collateral veins, venous ulceration.

Question 24

What investigations can you do to look for VTE?

Answer 24

Pre-test probability score: D-dimer.
Ultrasound: compressilbity (compress vein, if compressible unlikely DVT), doppler ultrasound (can see flow inside vein).
CXR: usually normal in PE, can show pleural effusions and occassionaly infarct.
V/Q scan: limited by frequency of inconclusive results.
CTPA: gold standard.

Question 25

What is the negative and positive predictive value of d-dimer for VTE?

Answer 25

High negative, low positive (if it is negative you are very unlikely to have it).

Question 26

With the Well's score, what would you do if probability was low?

Answer 26

Check d-dimer, no imaging if negative.

Question 27

With the Well's score, what would you do if probability was moderate/high?

Answer 27

Need imaging regardless of d-dimer (negative imaging and positive d-dimer requires repeat imaging).

Question 28

What values of the Well's score mean PE likely or unlikely?

Answer 28

4 or less is unlikely, greater than 4 is likely.

Question 29

What are the risk factors/symptoms involved in the revised geneva score?

Answer 29

Age, previous DVT/PE, surgery or leg immobility in the last month, active malignant condition, unilateral limb pain, haemoptysis.

Question 30

What are the signs involved in the revised geneva score?

Answer 30

Tachycardia, pain on lower limb deep venous palpation and unilateral oedema.

Question 31

What are the mechanical interventions for DVT and PE?

Answer 31

Graduated compression stockings, IVC filters.

Question 32

Why is treatment of drug use associated VTE complicated?

Answer 32

Risk of haemorrhage vs embolic disease, give rivaroxaban or fragmin. If retired injector may think about lifelong anticoagulants.

Question 33

What drugs should you use in cancer associated VTE?

Answer 33

Weight adjusted fragmin.

Question 34

What is phlegmasia?

Answer 34

Arterial compromise secondary to extensive DVT.

Question 35

What DVT patients would you consider for thrombolysis?

Answer 35

Patients with sumptomatic iliofemoral DVT symptoms less than 14 days duration with good functional states, a life expectancy of 1 year or more and a low risk of bleeding.

Question 36

What patients with PE would you offer thrombolysis?

Answer 36

Patients with PE and haemodynamic instability.

Question 37

How long after thrombosis should compression stockings be worn?

Answer 37

2 years.

Question 38

What do compression stockings remain the only treatment for?

Answer 38

Post-phlebitic syndrome.

Question 39

When would you use an IVC filter?

Answer 39

In patients with proximal DVT or PE who cannot have anticoagulation. Patients with recurrent proximal DVT or PE despite adequate anticoagulation only after considering increasing target INR or LMWH.

Question 40

Why are IVC filters not an ideal replacement for anticoagulation?

Answer 40

They often have complications.