Definitions & Etiology

the formation of one or more blood clots in a deep vein, typically of the lower extremities

• Proximal DVT: DVT of the lower extremity affecting the femoral vein, profunda femoris vein, and/or the popliteal vein (up to the calf vein trifurcation)

• Distal DVT: DVT of the lower extremity that is confined to the veins beyond the calf vein trifurcation (i.e., below the knee joint)

an umbrella term that encompasses DVT and pulmonary embolism (PE)

• Recurrent VTE: VTE that recurs in a patient after the completion of the first 2 weeks of antithrombotic therapy.

• Provoked VTE: VTE in an individual with ≥ 1 risk factor for VTE

• Unprovoked VTE (idiopathic VTE): VTE in an individual without risk factors for VTE

• Surgical factors

  • Surgery under general anesthesia

  • Cesarean delivery

• Immobilization

  • Acute illness requiring complete bed rest

  • Lower extremity injury with restricted mobility for ≥ 3 days

  • Long-distance travel

• Estrogen-related factors

  • Pregnancy

  • Use of OCPs or HRT

• Intravascular devices, such as:

  • Indwelling venous catheter

  • Implanted pacemaker or cardiac defibrillator leads

• Patient factors

  • Obesity

  • Smoking

  • IV drug use

  • Nonadherence to VTE prophylaxis

• Patient factors

  • Age > 60 years

  • Personal or family history of DVT or PE [8]

• Prothrombotic chronic illnesses

  • Active cancer

  • Nephrotic syndrome [9]

  • Autoimmune disorders

    • APLA syndrome

    • Inflammatory bowel disease

  • Hereditary thrombophilia

    • Factor V Leiden

    • Antithrombin III deficiency, protein C deficiency, and protein S deficiency

    • Prothrombin mutation

Remember DVT risk factors using the mnemonic “THROMBOSIS”: Travel, Hypercoagulable/HRT, Recreational drugs, Old (> 60), Malignancy, Blood disorders, Obesity/Obstetrics, Surgery/Smoking, Immobilization, Sickness (CHF/MI, IBD, nephrotic syndrome, vasculitis)!

The Virchow triad refers to the three main pathophysiological components of thrombus formation.

1. Hypercoagulability: increased platelet adhesion, thrombophilia (e.g., factor V Leiden mutation), use of oral contraceptives, pregnancy

2. Endothelial damage: Inflammatory or traumatic vessel injuries can lead to activation of clotting factors through contact with exposed subendothelial collagen.

3. Venous stasis: varicosis, external pressure on the extremity, immobilization (e.g., hospitalization, bed rest, long flights or bus rides), local application of heat

To remember the three pathophysiological components of thrombus formation, think: “HE'S Virchow”: H-Hypercoagulability, E-Endothelial damage, S-Stasis