Venous Thromboembolism

Venous Thromboembolism

 

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

Epidemiology

  • Incidence
    • 100/100,000 per year venous thromboembolic disease (VTE)
    • Estimated 5 million DVT patients annually
    • 500,000 pulmonary emboli (PE) develop from these DVTs
  • Age – greatest risk in older patients
  • Gender – M:F; equal
  • 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 – most common in orthopedic surgeries
  • Neoplasms – highest risk in pancreas, ovary, lung, urinary tract, breast and stomach
    • Odds ratio of  7.0
  • Trauma – fractures of the spine and lower extremities are highest risk
  • 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

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

  • 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

Diagnosis

  • May mimic other conditions, so a high index of suspicion is necessary; use of Wells Prediction Rule tables to establish pretest probability

Wells Clinical Model for Predicting Pretest Probability for Deep-Vein Thrombosis

Clinical Characteristic

Score

Active cancer (treatment ongoing, within previous 6 months, or palliative)

1

Paralysis, paresis, or recent plaster immobilization of the lower extremities

1

Recently bedridden >3 days or major surgery within 12 weeks requiring general or regional anesthesia

1

Localized tenderness along the distribution of the deep venous system

1

Entire leg swollen

1

Calf swelling 3 cm larger than asymptomatic side (measured 10 cm below tibial tuberosity)

1

Pitting edema confined to the symptomatic leg

1

Collateral superficial veins (nonvaricose)

1

Alternative diagnosis at least as likely as deep venous thrombosis

-2

Note: Clinical probability: low ≤0; intermediate 1-2; high ≥3.  In patients with symptoms in both legs, the more symptomatic leg is used.

(Wells, et al., 1997, 1796)

Wells Prediction Rules for Diagnosing Pulmonary Embolism:  Suspect Pulmonary Embolism

Clinical Characteristic

Score

Previous pulmonary embolism or deep vein thrombosis

+1.5

Heart rate >100 beats per minute

+1.5

Recent surgery or immobilization

+1.5

Clinical signs of deep vein thrombosis

+3

Alternative diagnosis less likely than pulmonary embolism

+3

Hemoptysis

+1

Cancer

+1

Note: Clinical probability of pulmonary embolism: low 0-1; intermediate 2-6; high ≥7.

(Chagnon, et al., 2002, 270)

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(+) pretest probability virtually excludes DVT)
      • However, false-positives may occur
      • When test is combined with clinical criteria, results are helpful
    • D-dimer is sensitive but not specific for DVT and PE
  • Gold standard testing is venography for DVT, angiography or helical CT for PE
  • PIOPED II has recommendations for PE diagnosis using certain algorithms for low, moderate and high probability risk categories

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

See Also