II. Epidemiology

  1. Patients with VTE and no risk Factors under age 40 years: 28%

III. Pathophysiology: Virchow's Triad

  1. VTE is caused by at least one of three dysfunctions
    1. Hypercoagulability
    2. Blood flow alterations
    3. Endothelial injury or dysfunction

IV. Risk Factors: Venous Thromboembolism By Strength of Risk

  1. Strong Risk Factors (Odds Ratio >10)
    1. Hip Fracture (or leg Fracture)
    2. Total Hip Arthroplasty (THA)
    3. Total Knee Arthroplasty (TKA)
    4. Major general surgery
    5. Major Trauma
    6. Spinal cord injury
  2. Intermediate Risk Factors (Odds Ratio 2-9)
    1. Arthroscopic knee surgery
    2. Central venous catheters (e.g. femoral line)
    3. Chemotherapy
    4. Chronic Heart Failure
    5. Respiratory failure
    6. Hormone Replacement Therapy
    7. Oral Contraceptives
    8. Malignancy
    9. Cerebrovascular Accident with Hemiplegia
    10. Pregnancy or postpartum
    11. Thrombophilia
    12. Prior Venous Thromboembolism
  3. Weak Risk Factors(Odds Ratio <2)
    1. Bed rest >3 days
    2. Car or air travel >8 hours (or other prolonged sitting)
    3. Advanced age
    4. Laparoscopic surgery
    5. Morbid Obesity (BMI >40)
    6. Varicose Veins
  4. References
    1. Anderson (2003) Circulation 107(23 suppl 1): 19-116 [PubMed]

V. Risk Factors: Initial Venous Thromboembolism by chronicity

  1. Major transient risks
    1. Hospitalization
    2. Plaster cast immobilization
    3. Surgery
    4. Trauma
  2. Minor transient risks
    1. Prolonged travel >2 hours (risk increases 18% for every 2 hours traveled)
    2. Pregnancy
    3. Oral Contraceptives or other hormone therapy
  3. Persistent risks
    1. Collagen vascular disease
    2. Heart Failure
    3. Cancer
    4. Myeloproliferative disorders
    5. Nephrotic Syndrome
    6. Recurrent Pregnancy Loss

VI. Risk Factors: Recurrent Thromboembolism after stopping Anticoagulants (Relative Risk)

  1. Metastatic cancer (6-9)
  2. Factor VIII >200 IU/dl (6)
  3. Non-metastatic Cancer (3)
  4. Antiphospholipid Antibody Syndrome (2.5)
  5. D-Dimer increase after acute therapy completed (2.2)
  6. Persistent risk factors - see above (2)
  7. Idiopathic VTE (2)
  8. Protein C,Protein S and Antithrombin deficiency (1.8)
  9. Prothrombin mutation - G20210A (1.7)
  10. Homozygous for Factor V Leiden (1.6)
  11. Second VTE (1.5)
  12. Mild Hyperhomocysteinemia (0.9)
  13. Distal VTE (0.5)
  14. Transient risk factors (0.5)
  15. Kearon (2008) Chest 133(6 suppl):454S [PubMed]

VII. Risk Factors: Venous Stasis

  1. Prolonged immobility
  2. Long leg Fracture or other limb immobilization
  3. Paralysis
    1. Cerebrovascular Accident (CVA)
    2. Spinal cord injury
  4. Varicose Veins
    1. High risk for DVT in surgery without DVT Prophylaxis
  5. Obesity
  6. Cardiac Disease
    1. Congestive Heart Failure
    2. Atrial Fibrillation
    3. Myocardial Infarction

VIII. Risk Factors: Hypercoagulable

  1. Hypercoagulable state
    1. See Thrombophilia
    2. Inherited cause found in up to one third of DVT cases
      1. Mateo (1997) Thromb Haemost 77:444-51 [PubMed]
  2. Prior Deep Vein Thrombosis (DVT)
  3. Medications
    1. Increased Estrogen
      1. Oral Contraceptive or Estrogen Replacement
      2. Pregnancy
      3. Tamoxifen (Nolvadex)
    2. Hydralazine
    3. Phenothiazines
    4. Procainamide
  4. Major Trauma
  5. Recent Surgery
  6. Autoimmunity (e.g. Systemic Lupus Erythematosus)
  7. Cancer
    1. Colon Cancer
    2. Ovarian Cancer
    3. Multiple Myeloma
    4. Consider evaluation for occult cancer in DVT
  8. Chemotherapy
  9. Inflammatory Bowel Disease
  10. Polycythemia
  11. Sickle Cell Anemia
  12. Nephrotic Syndrome
  13. History of thromboembolic disease
    1. Deep Venous Thrombosis
    2. Pulmonary Embolus
  14. Type A Blood

IX. Risk Factors: Intimal damage

  1. Local Trauma
  2. Surgery (Especially General and Orthopedic Surgery)
    1. General anesthesia is an independent risk factor
    2. Consider DVT Prophylaxis
  3. Penetrating vessel injury
    1. Intravenous Drug Abuse
    2. Central Line Placement
      1. Especially femoral Central Line

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