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Updated: Aug 9 2021

Pulmonary Thromboembolism

  • Introduction
    • Defined as occlusion of a pulmonary artery from embolization of a thrombus from a distal site
      • size of embolism determines proximity of occlusion to pulmonary trunk
        • Saddle embolus
          • large clot that occludes central pulmonary arteries
      • most commonly due to a thromboembolism from the deep veins of the leg
        • highest number originate from femoral vein
    • Risk factors
      • Virchow's triad
        • stasis
          • immobility
          • CHF
          • obesity
          • surgery
        • hypercoagulability
          • pregnancy
          • protein C/S deficiency
          • factor V Leiden
          • severe burns
          • cancer
        • endothelial damage
          • exposed collagen stimulates clotting cascade
            • trauma
            • fracture
            • previous DVT
  • Presentation
    • Dyspnea and tachycardia common presenting findings
    • May see hypoxemia on pulse oximetry and ABG
      • ABG often shows ↓ PO2, ↓ PCO2, ↑ A-a gradient
    • Pleuritic chest pain
    • Sudden death
      • acute right heart failure from rapid increase in pulmonary artery pressure
      • more common with saddle embolism
    • Pleural friction rub
    • Fever
      • if pulmonary infarct
    • Deep vein thrombosis
      • Homans' sign
        • dorsiflexion of foot leads to tender calf muscle
        • not present in the majority of cases (not sensitive or specific)
      • erythematous, swollen, warm, lower extremity
  • Imaging
    • Chest CT with angiography
      • test of choice in most circumstances
      • visualize filling defect in pulmonary artery
    • V/Q radionuclide scan
      • ↓ pulmonary perfusion without decreased ventilation to given area
      • used when patient cannot tolerate CT contrast (renal failure, pregnancy)
      • requires a normal chest xray to be useful
    • pulmonary angiogram
      • gold-standard confirmatory test
      • rarely used
  • Studies
    • Labs
      • serum D-dimers
        • result of clot degradation
        • only useful if low pretest probability (Wells criteria)
          • high sensitivity but low specificity
  • Treatment
    • Pharmacologic
      • anticoagulation
        • heparin or low-molecular weight heparin (LMWH)
        • warfarin
          • begin for long term anticoagulation
      • thrombolysis
        • in cases of hemodynamic compromise
    • Operative
      • inferior vena cava filter
        • indicatied if anticoagulation is contraindicated or if patient develops a PE while on anticoagulants
      • thrombectomy
        • in cases of hemodynamic compromise and contraindication to thrombolytic therapy
    • Prevention
      • Subcutaneous heparin or LMWH most effective for immobile patients or patients at high risk
      • early ambulation as able
      • Sequential compression devices when pharmacologic prophylaxis is contraindicated
  • Complications
    • Pulmonary infarction
      • most cases do not result in infarction due to large degree of collateral circulation in the lungs
      • occur when patient has a reduction in pulmonary blood flow
        • secondary to decreased cardiac output or obstructive lung disease
    • Death
      • Due to right ventricular failure
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