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Updated: Jun 3 2024

Pulmonary Embolism

  • Snapshot
    • A 36-year-old woman presents to the emergency department with worsening shortness of breath and pleuritic chest pain. Her symptoms began earlier in the day while she was waiting for her bus to return home. She recently returned from China to the United States for a business meeting. She denies any sick contacts and has not had these symptoms in the past. Medical history is unremarkable. She takes an oral contraceptive and a daily multivitamin. Her temperature is 98.6°F (37°C), blood pressure is 135/82 mmHg, pulse is 112/min, respirations are 24/min, and oxygen saturation is 89% on room air. A CT angiogram performedmed and demonstrates a filling defect in the pulmonary vasculature. She is immediately started on supplemental oxygen and heparin.
  • Introduction
    • Definition
      • mechanical obstruction of the pulmonary vascular secondary to a blood clot
        • typically the blood clot is a thromboembolism from a deep vein thrombosis (DVT)
  • Epidemiology
    • Risk factors
      • prolonged immobilization (e.g., long travel)
      • malignancy
      • thrombophilia
      • pregnancy
      • hormonal contraceptives
  • Etiology
    • DVT (most common)
      • from the veins of the proximal thigh (iliac, femoral, or popliteal)
    • Phlegmasia cerulea dolens
      • a progression from a DVT
      • massive thrombus that can embolize from the proximal ileofemoral vein
      • enlarged, blue, and tender lower extremity
    • Septic embolism from right-heart endocarditis
    • Fat embolism
    • Amniotic fluid embolism
    • Pathophysiology
      • occlusion of the pulmonary vasculature results in hypoxemia and subsequent pulmonary vasoconstriction
        • the increased pulmonary constriction causes an increase in pulmonary vascular resistance, which decreases right ventricular stroke volume leading to
          • increased ventricular oxygen demand
          • right ventricular dilatation
          • decreased left ventricular preload (leading to circulatory failure)
          • poor blood flow to the lung, leading to a ventilation-perfusion mismatch
  • Presentation
    • Symptoms
      • dysnea (most common)
      • pleuritic chest pain
      • cough
      • hemoptysis
      • syncope in cases of a large PE
    • Physical exam
      • tachypnea
      • tachycardia
      • loud P2
      • hemodynamic instability in cases of a large PE
  • Imaging
    • CT angiography of the chest
      • indication
        • imaging study of choice in the diagnostic evaluation of PE
          • sensitivity of ~90%
          • specificity of ~95%
      • comments
        • chest radiography is typically normal or it may show
          • pleural effusions
          • Hampton hump (wedged-shaped infarct)
          • Westermark sign (avascularity distal to the PE)
    • V/Q scan
      • indication
        • performed if the pre-test probability of PE is high but the patient cannot undergo a CT angiogram (e.g., renal failure, pregnancy, or unavailability) 
      • interpretation
        • normal
          • rules out PE
        • high-probability
          • treat with heparin
        • low or intermediate probability
          • if clinical suspicion is high, then get a pulmonary angiography
    • Venous duplex ultrasound of the lower extremities
      • indication
        • to evaluate if there are DVTs
  • Studies
    • ECG
      • findings
        • sinus tachycardia
        • atrial fibrillation
        • right ventricular strain
        • S1Q3T3 
          • presence of S wave in lead I and Q wave and inverted T wave in lead III
        • T-wave inversions in V1-V4
    • Arterial blood gas 
      • findings
        • hypoxemia
        • hypocapnia
        • respiratory alkalosis
        • alveolar-arterial gradient may be elevated
    • D-dimer
      • has a high sensitivity but poor specificity for PE and a high negative predictive value
        • used to rule-out PE if there is a low pre-test probability
          • a positive D-dimer in a low risk patient must be followed by a confirmatory study (CTA chest)
  • Differential
    • Myocardial infarction
      • differentiating factor
        • coronary angiography demonstrating coronary occlusion
    • Costochondritis
      • differentiating factor
        • pain with palpation or movement of the arm
  • Treatment
    • Medical
      • Non-vitamin K anticoagulation
        • indication
          • initial therapy in patients with PE in order to prevent further clot formation
            • treatment should not be delayed
        • medication options (best initial step in high risk patient with obvious PE)
          • low-molecular weight heparin
            • do not give in renal failure
          • unfractionated heparin
            • dose by monitoring aPTT
            • preferred in kidney injury/failure
      • warfarin
        • indication
          • typically given around the same time as a non-vitamin K anticoagulant is given
            • dose based on INR (goal is 2-3)
      • thrombolytic therapy
        • indication
          • performed in patients with PE who are hemodynamically unstable
    • Operative
      • embolectomy
        • indication
          • performed in patients with PE who are hemodynamically unstable and thrombolytic therapy is contraindicated or who fail thrombolysis
      • IVC filter
        • indication
          • performed in patients with PE who have a contraindication or failure of anticoagulation
  • Prognosis
    • Significantly high mortality without treatment
    • Wells' criteria
      • used to assess for risk of pulmonary embolism (sum the points)
        • signs and symptoms of DVT +3
        • pulmonary embolism (PE) is the most likely diagnosis +3
        • pulse is 100/min +1.5
        • surgery within the past 4 weeks or immobilization for the past 3 days + 1.5
        • previously diagnosed PE or DVT + 1.5
        • hemoptysis +1
        • malignancy with treatment in the past 6 months
      • < 2 points
        • low risk
        • 1.3% incidence of PE
        • consider using d-dimer
      • 2-6 points
        • moderate risk
        • 16.2% incidence of PE
        • consider high sensitivity d-dimer or CTA
      • > 6 points
        • high risk
        • 37.5% incidence of PE
        • consider CTA
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