Deep Vein Thrombosis
A blood clot in a deep vein, usually in the leg, that can cause local damage or break off and travel to the lungs.
Emergency Management: Acute massive pulmonary embolism causing right heart failure, hypotension, or cardiac arrest.
Deep Vein Thrombosis (DVT) is the formation of a blood clot (thrombus) within a deep vein, predominantly in the legs (e.g., popliteal, femoral, or iliac veins). It is part of the venous thromboembolism (VTE) spectrum and can lead to life-threatening pulmonary embolism if the clot embolizes.
Detailed Overview
DVT pathophysiology is classically described by Virchows triad: venous stasis, endothelial injury, and hypercoagulability. The condition often begins in the calf veins and propagates proximally. Prompt diagnosis is critical to prevent acute pulmonary embolism (PE) and long-term post-thrombotic syndrome (PTS), which causes chronic leg swelling, pain, and ulceration.
Epidemiology & Demographics
Annual incidence is approximately 1 per 1,000 adults. Incidence increases exponentially with age, reaching 1 in 100 for those over 80 years. Slight male predominance in older ages. Post-thrombotic syndrome affects up to 50% of patients within 2 years of proximal DVT.
Etiological Mechanism
Provoked DVT arises from transient risk factors like major surgery, trauma, or immobilization. Unprovoked DVT has no identifiable transient risk factor and is often linked to underlying occult malignancy or inherited thrombophilia (e.g., Factor V Leiden).
Primary Causes
Prolonged bed rest, orthopedic surgery (hip/knee arthroplasty), cancer (e.g., pancreatic, lung), oral contraceptives, Factor V Leiden mutation, Prothrombin G20210A mutation, antiphospholipid syndrome.
Thrombogenesis is triggered by endothelial activation (due to hypoxemia from stasis or direct injury), leading to surface expression of tissue factor. This initiates the coagulation cascade. Fibrin network traps red blood cells and platelets, forming a red thrombus. As the thrombus grows, it obstructs venous return, increasing venous pressure, which causes fluid transudation and clinically apparent edema. Thrombus propagation into larger proximal veins increases the risk of macro-embolization to the pulmonary arteries.
Diagnostic Criteria & Guidelines
Diagnosis is based on a structured clinical probability assessment (e.g., Wells Score). If low probability, D-dimer < 500 ng/mL rules out DVT. If high probability or positive D-dimer, diagnosis is confirmed via venous compression ultrasonography showing non-compressibility of a deep vein.
Direct oral anticoagulants (DOACs): Apixaban 10 mg PO BID for 7 days, then 5 mg PO BID; or Rivaroxaban 15 mg PO BID for 21 days, then 20 mg PO daily. Treatment duration is at least 3 months. In patients with cancer-associated DVT, DOACs or Low Molecular Weight Heparin (LMWH) like Enoxaparin 1 mg/kg SQ Q12H is preferred.
Second-Line & Adjunctive Therapy
Vitamin K antagonist (Warfarin) bridged with LMWH or Unfractionated Heparin until INR is therapeutic (2.0-3.0) for two consecutive days. Used if DOACs are contraindicated (e.g., severe renal impairment CrCl < 15 mL/min or antiphospholipid syndrome).
Surgical & Procedural Management
Catheter-directed thrombolysis (e.g., with tPA) or mechanical thrombectomy is reserved for severe iliofemoral DVT or phlegmasia cerulea dolens to prevent limb loss. Inferior Vena Cava (IVC) filter placement if anticoagulation is absolutely contraindicated.
Patient Counseling & Advice
Educate on signs of bleeding and when to seek emergency care. Advise against contact sports while on anticoagulants. Discuss the importance of strict adherence to medication to prevent recurrence or PE.
Follow-Up & Monitoring Schedule
Re-evaluate at 3 months to decide on stopping or extending anticoagulation based on bleeding risk vs. recurrence risk. Regular monitoring of renal function if on DOACs, or INR monitoring (target 2.0-3.0) if on warfarin.
Preventive Strategies
In-hospital thromboprophylaxis with Enoxaparin 40 mg SQ daily or unfractionated heparin 5000 units SQ Q8H for high-risk medical/surgical patients. Intermittent pneumatic compression devices if bleeding risk is high.
With prompt anticoagulation, the acute mortality is very low (<1%). Without treatment, risk of symptomatic PE is up to 50%. Recurrence risk is ~30% over 10 years for unprovoked DVT.