Deep vein thrombosis (DVT)

Question 1

What is Virchow’s Triad? (3)

Answer 1

1. Alteration in blood flow - stasis, turbulence.
2. Alterations in blood constituents (i.e. inherited or acquired hypercoagulable - sticky)
3. Vascular endothelial injury - blood vessel wall damage

Question 2

What are the sequelae of DVT? (consequences) (3)

Answer 2

Venous insufficiency
> hyper-pigmentation
> limb pain (nerve damage) and swelling (inflammatory infiltrate)
> dermatitis, ulcers, gangrene

Recurrent DVT

Pulmonary embolism

Question 3

What is a thrombosis?

Answer 3

a pathological intravascular solidification of blood constituents

Question 4

What is an embolism?

Answer 4

a vascular obstruction at a site distant from the origin of the embolus

Question 5

What are the acquired risk factors for VTE?

Answer 5

• Malignancy
• Surgery
• Immobility
• Trauma
• Pregnancy
• OCP (oral contraceptive pill)
• HRT (hormone replacement therapy)
• Obesity
• Previous VTE

LONG HAUL FLIGHT - immobility

• Other chronic illnesses:
  »> HF, inflammatory bowel disease, nephrotic syndrome, antiphospholipid syndrome, myeloproliferative disorders.

Question 6

Why is malignancy a risk factor for VTE?

Answer 6

Blood is in a hypercoagulable state due to production of substances with pro-coagulable activity: tissue factors.

Question 7

Why is surgery a risk factor for VTE?

Answer 7

orthopaedic (hip fracture, knee replacement), major vascular surgery, cancer surgery
> causes immobility after surgery
> increased inflammatory markers

Question 8

Why is pregnancy a risk factor for VTE?

Answer 8

there is physical obstruction to veins

hormone changes cause blood to be in hypercoagulable state

Question 9

What are the inherited risk factors for VTE?

Answer 9

• Factor V Leiden mutation
  (Va encourages prothrombin to thrombin. mutated can’t be broken down by protein C)
• Prothrombin gene mutation
  increase in prothrombin
• Protein S deficiency
  needed to activate protein C
• Protein C deficiency
  excessive clotting caused as Protein C is used to break down Va which encourages prothrombin to thrombin.

Antithrombin III deficiency - III inactivates thrombin.

Question 10

What are the signs and symptoms of DVT? (6)

Answer 10

pain
tenderness
swelling
erythema (red rash)
heat
venous engorgement

Question 11

What diagnostic tests are used to identify DVT? (2)

Answer 11

D-dimer (blood test)
USS/Doppler (ultrasound)

could use venogram - iodine contrast then radiogram

Question 12

What is a D-dimer test?

Answer 12

It is useful when negative as it rules out DVT

Product of thrombus fibrinolysis. Plasmin enzyme breaks down fibrin mesh..but is unable to break bonds btw one E and two D units. Remaining protein fragment = D-dimer

False positives due to inflammation, trauma, surgery, malignancy, pregnancy, recent surgery.
False negative if sample taken too early or late.

Question 13

Why is heparin an anticoagulant?

Answer 13

Heparin enhances activity of antithrombin III.
This leads to inactivation of thrombin.
Anticoagulant

Question 14

What is a major risk factor for venous thromboembolism?

Answer 14

malignancy