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Saturday, August 16, 2025

DVT (deep vein thrombosis)


Introduction

Deep Vein Thrombosis (DVT) is the formation of a blood clot (thrombus) within a deep vein, most commonly in the lower extremities (calf, thigh, or pelvis). It is a major component of venous thromboembolism (VTE), which includes both DVT and pulmonary embolism (PE). DVT is considered a serious medical condition because clots can dislodge and travel to the lungs, leading to PE—a potentially fatal complication.

The condition is highly relevant in both inpatient and outpatient settings and poses significant morbidity, mortality, and economic burden worldwide. Early recognition, prompt treatment, and secondary prevention are critical.

Epidemiology

  • Annual incidence: Approximately 1–2 cases per 1,000 population.

  • Lifetime risk: 2–5% in the general population.

  • More common in older adults (risk doubles with each decade after age 50).

  • Higher incidence in hospitalized and post-surgical patients.

  • Slightly more common in men than women after middle age.

  • Significant recurrence risk: 20–30% within 10 years of the first episode.

Pathophysiology

The development of DVT is explained by Virchow’s triad:

  1. Venous stasis

    • Immobility, long-haul flights, prolonged bed rest.

    • Paralysis, casting of limbs.

  2. Endothelial injury

    • Trauma, surgery, catheter placement.

    • Inflammatory diseases, chemotherapy.

  3. Hypercoagulability

    • Inherited thrombophilias (e.g., Factor V Leiden mutation, Prothrombin G20210A mutation).

    • Acquired risks (e.g., malignancy, pregnancy, oral contraceptive pills, hormone replacement therapy).

Thrombosis usually begins in valve pockets of deep veins where blood flow is sluggish. Fibrin, platelets, and trapped red cells form the thrombus, which may propagate proximally and embolize.

Risk Factors

1. Transient (Acquired)

  • Surgery, particularly orthopedic (hip/knee replacement).

  • Trauma and fractures.

  • Hospitalization, immobility.

  • Pregnancy and postpartum period.

  • Long-distance travel.

  • Central venous catheters.

2. Chronic/Underlying

  • Malignancy.

  • Inflammatory bowel disease.

  • Obesity.

  • Smoking.

  • Chronic venous insufficiency.

  • Heart failure.

3. Genetic/Inherited Thrombophilia

  • Factor V Leiden mutation.

  • Prothrombin gene mutation.

  • Protein C deficiency.

  • Protein S deficiency.

  • Antithrombin deficiency.

Clinical Features

1. Symptoms

  • Unilateral leg pain (often calf or thigh).

  • Swelling of affected leg.

  • Warmth and erythema.

  • Heaviness or cramping.

2. Signs

  • Tenderness along the course of the vein.

  • Increased calf circumference compared to the contralateral leg.

  • Pitting edema.

  • Dilated superficial collateral veins.

Note: Up to 50% of patients may be asymptomatic, underscoring the importance of risk assessment.

Complications

  1. Pulmonary Embolism (PE) – potentially fatal, occurs if clot dislodges.

  2. Post-thrombotic syndrome (PTS) – chronic pain, edema, skin changes, venous ulcers.

  3. Recurrent DVT – higher risk in unprovoked cases and thrombophilia.

  4. Chronic thromboembolic pulmonary hypertension (CTEPH) – rare but severe.

Diagnosis

1. Clinical Risk Assessment

  • Wells Score for DVT:

    • Active cancer, paralysis, bedridden, localized tenderness, swelling, collateral veins, previous DVT, alternative diagnosis less likely.

    • Score categorizes into “likely” or “unlikely.”

2. Laboratory Tests

  • D-dimer: Highly sensitive but not specific. A negative D-dimer effectively rules out DVT in low-risk patients.

3. Imaging

  • Compression Ultrasonography with Doppler – gold standard for initial diagnosis.

  • CT Venography or MR Venography – for pelvic/abdominal vein thrombosis or inconclusive ultrasound.

  • Contrast venography – rarely used, invasive.

Management and Treatment

1. General Principles

  • Prompt initiation of anticoagulation unless contraindicated.

  • Duration of therapy depends on whether the event was provoked (e.g., surgery, immobility) or unprovoked (idiopathic).

  • Prevention of complications (PE, PTS).

2. Anticoagulant Therapy

Anticoagulation is the mainstay of treatment.

a) Direct Oral Anticoagulants (DOACs) – First-line in most cases

  • Apixaban

    • Dose: 10 mg twice daily for 7 days, then 5 mg twice daily.

  • Rivaroxaban

    • Dose: 15 mg twice daily for 21 days, then 20 mg once daily.

  • Edoxaban

    • Dose: 60 mg once daily (after at least 5–10 days of parenteral anticoagulation).

  • Dabigatran etexilate

    • Dose: 150 mg twice daily (after at least 5–10 days of parenteral anticoagulation).

b) Vitamin K Antagonists (VKAs) – Warfarin

  • Warfarin sodium

    • Initial dose: 5 mg orally once daily, adjusted to maintain INR 2–3.

    • Requires overlap (“bridging”) with heparin for at least 5 days until INR therapeutic.

c) Heparins

  • Low-Molecular-Weight Heparin (LMWH)

    • Enoxaparin: 1 mg/kg subcutaneously every 12 hours OR 1.5 mg/kg once daily.

    • Dalteparin: 200 IU/kg once daily.

  • Unfractionated Heparin (UFH)

    • IV infusion, adjusted to maintain activated partial thromboplastin time (aPTT) 1.5–2.5× control.

  • Fondaparinux (synthetic factor Xa inhibitor)

    • Dose: 7.5 mg subcutaneously once daily (5 mg if <50 kg, 10 mg if >100 kg).

3. Duration of Anticoagulation

  • Provoked DVT (e.g., surgery, trauma): 3 months.

  • Unprovoked DVT: At least 3 months, often extended if bleeding risk is low.

  • Cancer-associated DVT: Extended anticoagulation (often with LMWH or DOAC).

  • Recurrent DVT or ongoing risk factors: Long-term or indefinite anticoagulation.

4. Thrombolysis and Interventions

  • Catheter-directed thrombolysis or systemic thrombolytics (e.g., Alteplase 100 mg IV infusion over 2 hours) reserved for extensive iliofemoral DVT with threatened limb viability.

  • Surgical thrombectomy – rarely indicated, for severe cases.

  • Inferior Vena Cava (IVC) Filters – indicated if anticoagulation is contraindicated or recurrent VTE despite therapy.

5. Adjunctive and Supportive Therapy

  • Compression stockings (30–40 mmHg) to reduce risk of post-thrombotic syndrome.

  • Mobilization is encouraged rather than bed rest once anticoagulated.

  • Pain relief with NSAIDs (e.g., ibuprofen 400 mg every 6–8 hours).

Prevention

1. Hospitalized Patients

  • Pharmacologic prophylaxis:

    • Enoxaparin 40 mg SC once daily, or

    • Dalteparin 5000 IU SC once daily, or

    • Fondaparinux 2.5 mg SC once daily.

  • Mechanical prophylaxis: Intermittent pneumatic compression devices, especially if bleeding risk is high.

2. Post-Surgical and Travel-Related

  • Early mobilization.

  • Adequate hydration.

  • Leg exercises during flights.

  • Graduated compression stockings.

Special Populations

1. Pregnancy

  • LMWH is preferred.

  • Warfarin and DOACs are contraindicated.

  • Dosing: Enoxaparin 1 mg/kg SC every 12 hours.

2. Cancer-Associated Thrombosis

  • Historically LMWH was standard; now DOACs (apixaban, rivaroxaban, edoxaban) are approved if bleeding risk is acceptable.

3. Renal Impairment

  • Avoid DOACs in severe renal impairment (CrCl <30 mL/min).

  • UFH is safer as it is not renally excreted.

Prognosis

  • With prompt treatment, prognosis is generally good.

  • Mortality: Low for isolated DVT but increases significantly if complicated by PE.

  • Recurrence: Higher in unprovoked DVT and patients with thrombophilia.

  • Long-term morbidity: Post-thrombotic syndrome in up to 50% of cases.

Future Directions

  • Biomarkers to predict recurrence risk and personalize anticoagulation duration.

  • Safer oral anticoagulants with lower bleeding risk.

  • Wearable technologies for early detection of stasis in at-risk populations.

  • Genetic screening in high-risk families.




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