Venous thrombosis (DVT) is the presence of thrombus in a vein and the accompanying inflammation.

Epidemiology

• Incidence
  • 100/100,000 per year for venous thromboembolic disease (VTE)
  • Estimated 5 million DVT patients annually
  • 500,000 pulmonary emboli (PE) develop from these DVTs
• Sex
  • Male - slightly more common
  • Female - more frequent during childbearing years
• Ethnicity
  • More common in Asian-Pacific islanders   
  • Less common in Hispanics (2 to 4 times lower risk than Caucasians and African Americans)

Risk Factors

• Surgery - highest risk for orthopedic surgeries
• Neoplasms - highest risk in pancreas, ovary, lung, urinary tract, breast and stomach
  • Odds ratio of  7.0
• Trauma - highest risk for fractures of the spine and lower extremities
• Pregnancy - highest risk in 1st and 3rd trimester
• Hormone use - postmenopausal replacement, oral contraceptives, tamoxifen citrate
  • Odds ratio of 2-4.0
• Immobilization - highest risk in acute myocardial infarction (MI), congestive heart failure (CHF) and stroke
• Hypercoagulable states - deficiencies of clotting factors including Protein C, S, antithrombin III; factor V Leiden, elevated levels of homocysteine
• Previous DVT or PE
  • Odds ratio as high as 15.6
• Indwelling catheters - most common source of upper extremity DVT
• Age - risk increases incrementally with increasing age

Pathophysiology

• Factors that predispose to DVT were first described by Virchow in 1856
  • Virchow triad - stasis, vascular damage and hypercoagulability
  •  Individual risk is the complex interaction of the above risk factors and congenital (inherited thrombophilia) factors

Clinical Presentation

• DVT
  • Extremity pain and swelling, warmth and erythema, pain in the calf with foot dorsiflexion (Homans sign)
    • Usually unilateral
  • Pulmonary embolism
    • Dyspnea, pleuritic chest pain, hemoptysis, low-grade fever, tachycardia, split S2 heart sound on cardiac auscultation

Treatment

• Therapy is necessary for proximal DVT
• Acute therapy:
  • Low molecular weight heparin or standard heparin therapy
  • More aggressive therapy is recommended for patients with large PEs/DVT and thrombolysis
    • Monitoring tests include PTT (unfractionated heparins) and anti-Xa (low molecular weight heparin)
• Chronic therapy requires oral warfarin for a varying period based on clinical history
  • Requires periodic monitoring of INR to ensure therapeutic range

Diagnosis

• Indications for testing - risk factors for VTE and other symptom such as shortness of breath, leg swelling/pain
• May mimic other conditions, so a high index of suspicion is necessary; use of Wells Prediction Rule tables to establish pretest probability

Refer to Venous Thromboembolism topic at www.arupconsult.com for Wells Clinical Model for Predicting Pretest Probability for Deep-Vein Thrombosis and for Wells Prediction Rules for Diagnosing Pulmonary Embolism: Suspect Pulmonary Embolism

• Laboratory testing
  • D-dimer testing in conjunction with duplex ultrasound for DVT (may also include ventilation perfusion scanning to rule out PE)
    • Used for excluding diagnosis (negative D-dimer plus low pretest probability virtually excludes DVT)
      • However, false-positives may occur
      • Results are most helpful when test is combined with clinical criteria
    • D-dimer is sensitive but not specific for DVT and PE; it should not be used to exclude VTE in patient with high pretest probability
• Imaging studies
  • Gold standard testing is venography for DVT, angiography or helical CT for PE
  • Doppler ultrasound has high sensitivity (89-100%) and specificity (86-100%) for proximal symptomatic DVT
  • PIOPED II has recommendations for PE diagnosis using certain algorithms for low, moderate and high probability risk categories
    • Negative D-dimer, low pretest probability and negative helical CT are associated with <1.5% subsequent fatal or nonfatal VTE