DVT

Question 1

What is the pathophysiology of a DVT?

Answer 1

Clotting in a deep vein of an extremity - usually calf or thigh, or the pelvis

Impaired venous return/venous stasis (1) leading to endothelial dsyfunction or injury (2), or hypercoagulabiltiy (3) = Virchow’s triad)

Question 2

What are some risk factors for DVT?

Answer 2

Hx DVT/PE

THROMBOSIS:

• Travel
• Hypercoagulable/HRT
• Recreational drugs
• Old >60
• Malignancy
• Blood disorders (esp factor V Leiden)
• Obesity/Obstetrics
• Surgery/Smoking
• Immobilisation
• ‘Sickness’ (CHF/MI, IBD, nephrotic syndrome, vasculits)

Question 3

How does DVT present?

Answer 3

(asymptomatic)

Localised, unilateral symptoms

More common in lower left extremity

Swelling,feeling of tightness/heaviness

Warmth erythema

Progressive tenderness, dull pain

Distension of superficial veins

Distal pules intact

Possible fever; signs of PE

Homan sign: calf pain on dorsal flexion of foot
Meyer sign: compression of calf causes pain
Payr sign: pain when pressure applied over medical part of the sole of the foot

Question 4

What are some subtypes of DVT?

Answer 4

Phlegmasia Cerulea Dolens:

• All veins in one extremity are obstructed + restriction of arterial flow
• High mortality
• Severe swelling, oedema, pain, cyanosis, cold, pulselessness
• Emergency surgery; fibrinolysis; amputation

Paget-Schroetter disease:

• Upper limb DVT - brachial, axial, subclavian
• Aetiology: repetitive effort induced thrombosis (e.g. weight lifting, operation of jackhammer), thoracic outlet syndrome; foreign body in vein (e.g. central venous catheter)
• Anticoag, fibrinolysis

Question 5

What is a DVT Well’s Score?

Answer 5

Probability of DVT given clinical features + Hx

Question 6

What does the DVT Well’s Score take into account?

Answer 6

Current/previous cancer treatment within 6 months
Bedridden >3days or major surgery within 4wks
Previous DVT
Symptoms
i) Calf swelling >3cm compared to other leg (measure 10cm below tibial tuberosity)
ii) Collateral (non varicose) superficial veins present
iii) Entire leg swollen
iv) Localised tenderness along deep venous system
v) Pitting oedema confined to symptomatic leg
vi) Paralysis, paresis or recent plaster immobilisation of lower extremity
Alternative diagnosis to DVT more likely
i) -2 points

Question 7

How do you investigate and treat someone with a high DVT Wells score?

Answer 7

0 = low risk, 1-2 = moderate, >3 = high risk
For people likely to have a DVT - proximal leg vein USS in <4hrs
For people unlikely to have DVT - D-dimer testing, if positive, refer to USS <4hrs
Dalteparin (LMWH)
Warfarin or rivaroxaban - INR (2-3)
Engage in regular walking, leg elevation and to delay long-haul aeroplane travel 2wks

Question 8

What is compression ultrasonography with Doppler?

Answer 8

Ultrasound (to visualise vein) + Doppler (to assess flow) - examiner applies gentle pressure to compressible veins using probe - +ve = noncompressibility of obstructed vein, visible hyperechoic mass, absent/abnormal flow on Doppler

Question 9

What is D-dimer testing ?

Answer 9

High sensitivity (95%) but low specificity (50%)

Good to rule out DVT - normal D-dimer = no DVT

But elevated D-dimer can be from other things e.g. infection recent surgery, or trauma, infection, liver or kidney disease, cancers, in normal pregnancy but also some diseases of pregnancy such as eclampsia

Question 10

What other tests might be indicated in DVT?

Answer 10

Venography/angiography:

• Most accurate assessment of calf veins/valve competency
• if obese, severe oedema, equivocal results in previous tests

CT:
- ?PE or underlying malignancy

Thrombophilia screen

General tumour screen:

• For idiopathic thrombosis (esp if >50yrs)
• U+E, LFT, urinalysis, CXR
• Ensure patient is up to date with screening e.g. bowel Ca colonoscopy

Question 11

What does a thrombophilia screen involve?

Answer 11

Indications:
-Young patients (40yrs), spontaneous VTE, unusual thrombus location, +ve FHx, Hx recurrent miscarriage/preeclampsia/abruption etc

Involves:

• FBC + Clotting - including ‘Activated Protein C Resistance’
• Protein C - Factor V Leiden (if APCR positive)
• Protein S - prothrombin gene mutation antithrombin
• Lupus anticoagulant - anticardiolipin antibodies
• Antiphospholipid antibodies

Timing:

• NEED TO BE PERFORMED AT LEAST 2WKS AFTER STOPPING ANTI-COAG BUT IDEALLY 4WKS
• Pregnancy, OCP, HRT, chemo - may all affect
• Avoid doing during intercurrent severe illness

Question 12

What are some differentials for DVT?

Answer 12

Superficial thrombophlebitis

• May co-exist with DVT (same risk factors) but rarely causes PE
• Presents similarly but with pain/erythema over a superficial vein, often palpable
• Clinical Dx, but duplex USS can support
• NSAIDs, compression + elevation of limp; LMWH if larger portions of vein affected

Question 13

How do you treat DVT?

Answer 13

Heparin - unfractionated or LMW:

• Given acutely
• Bolus + infusion over days
• Target - maintaining aPTT of 1.5x-2.5x the mean of the control value/upper limit of normal

Warfarin OR Xa inhibitor (rivaroxaban):

• Given as 2ndary prophylaxis
• INR 2-3 target; for 3-6months if 1st episode (indefinitely if 2nd)

Other treatment:

• Thrombolysis - if slow response to anticoag/PE with haemodynamic instability/proximal DVT of leg; e.g. streptokinase - given directly to site via venous catheter
• Thrombectomy
• Compression stockings/intermittent compression stockings