Deep vein thrombosis (DVT)

Overview

Deep vein thrombosis (DVT) is the formation of a thrombus within the deep venous system, most commonly affecting the lower extremities.

DVT is a major component of venous thromboembolism (VTE), which includes:

• Deep vein thrombosis (DVT).

• Pulmonary embolism (PE).

Approximately 90% of clinically significant pulmonary emboli originate from proximal DVT involving the popliteal, femoral, or iliac veins.

Untreated DVT may:

• Extend proximally.

• Embolize to the pulmonary circulation.

• Cause long-term complications such as post-thrombotic syndrome.

Pathophysiology

DVT formation is explained by Virchow’s triad:

• Venous stasis.

• Endothelial injury.

• Hypercoagulability.

Risk factors

Venous stasis

• Prolonged immobilization.

• Bed rest.

• Long-haul travel.

• Postoperative state, especially orthopaedic surgery.

• Stroke with limb paralysis.

• Heart failure.

Endothelial injury

• Trauma.

• Surgery.

• Central venous catheterization.

Hypercoagulability

• Malignancy.

• Pregnancy and postpartum state.

• Oral contraceptives or hormone replacement therapy.

• Obesity.

• Smoking.

• Inherited thrombophilias:

  • Factor V Leiden.

  • Protein C deficiency.

  • Protein S deficiency.

• Antiphospholipid syndrome.

• Previous history of VTE (strongest risk factor).

Clinical presentation

DVT may be asymptomatic or present with non-specific symptoms.

Common features include:

• Leg pain.

• Tenderness.

• Swelling, usually unilateral.

• Discoloration.

• Venous distention.

• Prominence of superficial veins.

• Cyanosis in severe cases.

• A palpable cord representing thrombosed vessels.

Important:

Clinical diagnosis of DVT alone is highly non-specific. Objective testing is required.

Classification

Proximal DVT

• Involves popliteal vein or above.

• Higher risk of pulmonary embolism.

Distal DVT

• Involves calf veins.

• Lower embolic risk.

Investigations

Laboratory tests

• D-dimer.

• PT.

• INR.

• aPTT.

• Complete blood count.

• Renal function tests before anticoagulation.

Imaging

• Compression duplex ultrasonography (Doppler USS):

  • First-line diagnostic test.

Other imaging options in selected cases:

• CT venography.

• MR venography.

• Venography (rarely used).

Management

Management aims to prevent:

• Clot extension.

• Recurrent venous thromboembolism.

• Pulmonary embolism.

Non-pharmacological management

• Limb elevation.

• Graduated compression stockings to reduce post-thrombotic syndrome.

• Early ambulation once anticoagulation is started.

Inferior vena cava (IVC) filter may be considered when:

• Anticoagulation is contraindicated.

Pharmacological treatment

Long-term anticoagulation is required.

Warfarin-based regimen

Warfarin is started with initial unfractionated heparin or enoxaparin therapy and overlapped for approximately 5 days.

• Warfarin PO 5 mg 24 hourly for 5 days.

AND

• Continue adjustment according to INR levels.

Duration:

• Usually 3–6 months depending on clinical risk.

Overlap with heparin/LMWH should continue until adequate anticoagulation is achieved.

Target INR:

• 2.0–3.0.

Low molecular weight heparin regimen

• Low molecular weight heparin SC 1 mg/kg 24 hourly for 5 days.

Alternative dosing:

• Enoxaparin SC 1 mg/kg 12 hourly may be used depending on clinical indication.

Unfractionated heparin regimen

• Unfractionated heparin IV 75 units/kg loading dose.

AND

• Continuous infusion 18 units/kg/hour.

Monitor:

• aPTT until therapeutic range is achieved.

Direct oral anticoagulant option

• Rivaroxaban PO 15 mg 12 hourly for 21 days.

THEN

• Rivaroxaban PO 20 mg 24 hourly for the remaining duration of treatment.

Adolescents and children

Options include:

• Unfractionated heparin IV loading dose 75 units/kg.

THEN

• 15–25 units/kg/hour by IV infusion.

OR

• 250 units/kg SC 12 hourly.

Pregnant women

Warfarin is teratogenic and should be avoided during pregnancy.

Use:

• Low molecular weight heparin SC 1 mg/kg 12 hourly for the whole duration of treatment.

Monitoring:

• Anti-Xa monitoring where available.

Monitoring during anticoagulation

Warfarin

• Monitor INR after initiation.

• Adjust dose according to INR.

Unfractionated heparin

• Monitor aPTT.

Low molecular weight heparin

• Consider anti-Xa monitoring in pregnancy or special situations.

Duration of anticoagulation

Depends on the cause:

• Provoked DVT:

  • Usually 3 months.

• Unprovoked DVT:

  • At least 6 months.

• Recurrent DVT:

  • Long-term anticoagulation.

• Cancer-associated thrombosis:

  • LMWH or DOAC for at least 6 months.

Complications

• Pulmonary embolism.

• Post-thrombotic syndrome.

• Chronic venous insufficiency.

• Recurrent VTE.

Prevention

Primary prevention

• Early mobilization after surgery.

• Mechanical compression devices.

• Prophylactic LMWH in high-risk hospitalized patients.

Secondary prevention

• Adequate duration of anticoagulation.

• Lifestyle modification:

  • Weight reduction.

  • Smoking cessation.