Venous Thrombosis

Question 1

Where do arterial events occur and where do venous events normally occur?

Answer 1

Arterial

• Coronary (MI)
• cerebral (stroke)
• peripheral (gangrene and loss of limb)

Venous

• Deep venous thromboses
• Pulmonary Embolism

Question 2

How do the walls of arteries and veins differ?

Answer 2

arteries = high pressure => very muscular wall

veins = low pressure => valves to prevent backflow

Question 3

How does clotting differ between an artery or a vein?

Answer 3

Arteries
- high pressure system ruptures atherosclerotic plaques in vessels

Veins

• stasis of blood activates the coagulation cascade
• no platelets are attracted as there is no “injury site”

Question 4

What are the components of Virchow’s triad and how do these relate to the clotting of blood?

Answer 4

• Stasis (low pressure venous system)
• vessel walls (deterioration of valves due to age/ previous blood clots)
• hypercoagulability (elevated clotting factor levels)

Question 5

HOw is venous thrombosis usually treated?

Answer 5

Anticoagulants e.g. heparin/warfarin/DOAC’s

Question 6

What are the clinical signs of a DVT?

Answer 6

Limb is:

• hot
• swollen
• tender
• potentially erythematous
• pitting oedema present

Question 7

What may be a differential diagnosis of a DVT based on the clinical signs?

Answer 7

Cellulitis

Question 8

Where in the lungs tends to be affected by a PE?

Answer 8

• infarcts usually occur in lung periphery

Question 9

What symptoms do patients usually experience in a PE?

Answer 9

• pleuritic chest pain (knife stuck into chest during every breath)
• cardiovascular collapse
• hypoxia
• Right sided heart strain (due to pumping blood against increased lung pressure => this can be seen on ECG/ECHO)

Question 10

What is the normal bacground risk of a patient experiencing a VTE?

Answer 10

Roughly 1/1000 patients per year
(young adults 1/10 000 and elderly 1/100)

Lifetime risk 2.5%

Question 11

What are the potential risk factors for developing a VTE?

Answer 11

• Age
• Obesity
• Pregnancy and Puerperium
• Oestrogen therapy (COCP/HRT)
• Previous DVT/PE
• Trauma/Surgery
• Malignancy
• Paralysis (limited mobility)
• Infection
• Thrombophilia

Question 12

Why are pregnant women and those in the puerperiium more at risk of a VTE?

Answer 12

Factor VIII levels rise up to 5x during pregnancy to prevent haemorrhage during childbirth

=> increased risk of clotting

Question 13

What happens in a thrombophilia which puts patients more at risk of clotting?

Answer 13

• familial disorder where coagulation activity is increased
• fibrinolytic activity decreased => clots can expand easier
• anticoagulation activity e.g. antithrombin/ Protein C/S may also be decreased (may be due to a deficiency)

Question 14

What happens in Factor V Leiden and how does this condition put patients at an increased risk of clotting?

Answer 14

Small change in Factor V protein
=> means the Proteins C/S struggle to switch it off efficiently
=> body is 5x more likely to clot

Question 15

Which of the risk factors for VTE are involved in blood STASIS?

Answer 15

Age
Obesity
Pregnancy
Previous DVT/PE
Trauma/Surgery
Malignancy
Paralysis

Question 16

Which of the risk factors for VTE are involved in VESSEL WALL damage/changes?

Answer 16

Age

Previous DVT/PE

Question 17

Which of the risk factors for VTE are related to HYPERCOAGULABILITY?

Answer 17

Age
Pregnancy
Puerperium
Oestrogen therapy (COCP/HRT)
Trauma/Surgery
Malignancy
Infection
Thrombophilia

Question 18

In what patients would you consider doing a hereditary thrombophilia screen?

Answer 18

• Venous thrombosis in patient <45 years
• Recurrent venous thrombosis
• Unusual venous thrombosis (e.g. in upper limb)
• FHx of venous thrombosis or thrombophilia

Question 19

HOw is a hereditary thrombophilia usually managed?

Answer 19

• Advice on avoiding risk (e.g. COCP not suitable)
• Short term prophylaxis (if periods of known risk e.g pregnancy)
• Short term anticoagulation (to treat thrombotic events)
• Long term anticoagulation (if recurrent VTE)

Question 20

Why do many patients with a hereditary thrombophilia not experience a thrombosis solely due to their condition?

Answer 20

Much more commonly occurs if combined with other risk factor

- e.g. COCP, surgery/procedure causing immobility etc

Question 21

What is the risk/ benefit analysis of long term anticoagulation?

Answer 21

Weighing up risk of thrombosis with the risk of serious haemorrhage

Question 22

GIve an example of an acquired thrombophilia?

Answer 22

Antiphospholipid antibody syndrome

- change in β2 glycoprotein 1

Question 23

Acquired thrombophilias have a stronger risk factor for thrombosis than the hereditary thrombophilias. TRUE/FALSE?

Answer 23

TRUE

Question 24

What are the main features of Antiphospholipid antibody syndrome?

Answer 24

Recurrent thromboses

• Arterial, including TIAs
• Venous
• Recurrent fetal loss (due to thrombosis in placenta)
  {babies carried to term may be SGA due to placental insufficiency}
• Mild thrombocytopenia

Question 25

Why is the APTT prolonged in Antiphospholipid Ab Syndrome if there is no clotting factor deficiency?

Answer 25

Lupus anticoagulant interferes with the test

=> prolongs the APTT

Question 26

Why is warfarin commonly used to treat Antiphospholipid Ab syndrome?

Answer 26

It has protection against arterial events as well as venous

=> useful as this condition experiences both

Question 27

What other conditions are associated with Antiphospholipid Ab syndrome?

Answer 27

• autoimmune
• lympho-proliferative (lymphoma, SLE)
• viral infection