What is Deep Vein Thrombosis?
Deep vein thrombosis (DVT) is the formation of a blood clot within a deep vein, most commonly in the proximal lower limb (popliteal, femoral, iliac veins). DVT is part of the venous thromboembolism (VTE) spectrum together with pulmonary embolism (PE). Untreated proximal DVT carries a 40–50% risk of PE. Upper extremity DVT (subclavian, axillary) accounts for 5–10% of DVTs and is increasingly associated with central venous catheters.
Pathophysiology
Virchow's triad: venous stasis, endothelial injury, and hypercoagulability. Venous stasis (immobility, surgery, travel) and hypercoagulability (malignancy, thrombophilia, pregnancy, OCP, obesity) are most common. Thrombus formation begins at venous valve pockets, propagates proximally, and can fragment to cause PE. Resolution occurs via fibrinolysis but post-thrombotic syndrome (pain, oedema, skin changes) affects 30–50% of DVT patients.
Clinical Features & Symptoms
- Unilateral leg swelling (calf, thigh, or entire leg)
- Unilateral leg pain or tenderness (calf tenderness on dorsiflexion — Homans sign, low sensitivity)
- Erythema and warmth over the thrombosed vein
- Palpable cord
- Often asymptomatic (50% of proximal DVT)
- Phlegmasia cerulea dolens (rare): massive DVT with limb ischaemia
Diagnosis
Wells DVT score to stratify pre-test probability. Low probability (score ≤0): D-dimer first; normal excludes DVT. Intermediate (score 1–2): D-dimer; if positive → ultrasound. High probability (score ≥3): compression duplex ultrasound directly. If ultrasound negative with high clinical suspicion: repeat ultrasound in 7 days or proceed to venography.
Current Treatment Guidelines
Anticoagulation — first-line (NOACs)
Class I, Level AApixaban 10 mg BD × 7 days then 5 mg BD, or rivaroxaban 15 mg BD × 21 days then 20 mg OD. Both approved for proximal DVT without need for initial LMWH (single-drug regimens). Preferred over LMWH/warfarin.
Treatment duration
Class I, Level A3 months minimum for provoked DVT (identifiable reversible risk factor). ≥3 months then reassess for unprovoked DVT. Indefinite anticoagulation for: recurrent unprovoked VTE, active malignancy, high thrombophilia risk (antiphospholipid syndrome, homozygous Factor V Leiden).
Extended anticoagulation with aspirin
Class IIb, Level BFor patients with unprovoked VTE who discontinue anticoagulation: aspirin 100 mg daily reduces recurrence by 32% vs placebo (ASPIRE, WARFASA). Lower efficacy than NOACs but suitable if anticoagulation not feasible.
Compression stockings
Class IIb, Level BKnee-length class II compression stockings not routinely recommended for post-thrombotic syndrome prevention (SOX trial: no benefit over no stockings). May be used for symptomatic leg oedema.
Malignancy-associated VTE
Class I, Level ADOACs (apixaban, rivaroxaban) preferred over LMWH for cancer-associated VTE. Avoid in luminal GI cancers (higher bleeding risk with DOACs). Indefinite anticoagulation while cancer active.
Monitoring & Treatment Targets
Repeat duplex ultrasound if symptoms not improving or worsening. Annual reassessment of anticoagulation duration need. Renal function review for NOAC dosing. Screen for occult malignancy in unprovoked DVT (clinical examination, age-appropriate cancer screening, FBC, LDH).
Key Clinical Trials
External Resources
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Frequently Asked Questions
How long should anticoagulation be continued after DVT?
A minimum of 3 months is recommended for all DVT. For provoked DVT (clear reversible cause such as recent surgery or trauma), 3 months is typically sufficient. For unprovoked DVT with no identifiable cause, extended anticoagulation should be considered after 3 months based on individual bleeding vs recurrence risk. Recurrent unprovoked DVT or antiphospholipid syndrome typically warrants indefinite anticoagulation.
What is the best anticoagulant for DVT?
Direct oral anticoagulants (DOACs) — apixaban and rivaroxaban — are first-line for DVT treatment in most patients. They are given as single-drug regimens (no initial LMWH needed), are non-inferior to LMWH/warfarin, and have significantly lower major bleeding rates. Apixaban (AMPLIFY trial) and rivaroxaban (EINSTEIN-DVT) are the most widely used.
Medical disclaimer: This content is intended for qualified healthcare professionals and does not constitute medical advice. Always apply clinical judgment and refer to current local guidelines and institutional protocols.