DVT

Question 1

Virchow’s triad:

Answer 1

Question 2

What tests can rule out DVT based on pre-test probability?

Answer 2

Wells 0= Low risk
5%
Can rule out with:
—> D dimer alone
—> 3-point POCUS

1-2= Mod risk
17%
Can rule out with:
—> High-sensitivity Ddimer alone
—> Whole leg USS

3 or more = High risk
Up to 50%
—> No role Ddimer
—> Whole leg USS alone
If doubt persists, repeat USS 5 days

Question 3

Role of Ddimer in DVT:

Answer 3

In low or moderate pretest probability (Wells 0-2), a negative D-dimer reduces risk to 1% and rules out DVT.

Low-sens only suitable in low risk
High-sens required for mod, high risk

Question 4

Age-adjusted D-dimer:

Answer 4

Normal is <0.5

After age 50, allowed to increase by 0.1 per decade and still be ‘normal’

ie. 0.7 okay for 70yo

Reasonable to apply to low/mod risk DVT work-ups

Question 5

Options when whole leg USS negative in high-risk patient, but still doubt:

Answer 5

Anticoagulate and repeat USS in 5 days.

Add D-dimer. If also negative, ruled out.

CT venogram.

Question 6

What is the risk of PE from below-knee DVT?

Answer 6

Around 5%

Up to 20% extend proximally- but this figure mostly from admitted patients

Question 7

Define ‘proximal’ DVT:

Answer 7

In or above popliteal vein

Question 8

Treatment of above-knee DVT:

Answer 8

Options:

Enoxaparin
Eg. 1mg/kg SC BD, or 1.5mg/kg SC daily.
–> Initial
–> Cancer patients

Heparin
Eg. 80units/kg bolus, 18units/kg/hr infusion
–> Target APTT 1.5x normaL
–> Renal failure

Warfarin (with enoxaparin bridging)
–> Target INR 2-3
–> Best if renal/ hepatic failure, need for reversal

Rivaroxaban - ONLY NOAC APPROVED for DVT
–> 15mg PO BD for 21 days, then 20mg daily for duration

*IVC filter

_______________

DURATION:
- 1st/ provoked = 3 months
- 6mo otherwise

+ Compression stocking ongoing (prevent post-phlebitic)

Question 9

Treatment of below-knee DVT:

Answer 9

Anticoagulate (as per above-knee)

OR

Serial USS
–> Repeat in 5-7 days
—–> Stop, repeat or Tx as per proximal.

Question 10

When should a SVT should be treated like a DVT?

Answer 10

Within 3cm of saphenofemoral junction

4 weeks anticoag

Question 11

Anticoagulation in pregnancy?

Answer 11

Enoxaparin preferred
–> Safe, effective.
*Heparin okay too

WARFARIN
and
DOACS
are CONTRAINDICATED
–> Teratogen
–> Stillbirth

Question 12

Which lower limb vessel gets unique consideration in thrombosis?

Answer 12

The ‘superficial femoral vein’, is a deep vein.

A superficial femoral vein thrombosis, is a DVT.