Vascular: Pulmonary Embolism (PE)

Basics

• Most Common Source: Iliofemoral DVT
• Risk for Sudden Cardiac Arrest & Circulatory Collapse
• 30% Mortality if Untreated

Physiology

• Mechanisms of Impaired Gas Exchange:
  • Mechanical/Functional Obstruction (Ventilation-Perfusion Mismatch)
  • Inflammation Causing Surfactant Dysfunction & Atelectasis (Functional Intrapulmonary Shunting)
• Impaired Gas Exchange Causes to Hypoxia
• Hypoxia Causes Tachycardia & Tachypnea
• Tachypnea Leads to Hypocapnia & Respiratory Alkalosis

Presentation

• Many are Asymptomatic
• Dyspnea – Most Common Symptom
• Pleuritic Chest Pain
• Cough
• Wheezing
• Hemoptysis
• Tachypnea
• Tachycardia
• Fever
• Symptoms of DVT

Wells Score

• Predicts Probability of PE
• Factors:
  • Physical Findings of DVT – 3 Points
  • No Better Alternative Diagnosis – 3 Points
  • Tachycardia (HR > 100) – 1.5 Points
  • Immobilization (≥ 3 Days) or Recent Surgery (< 4 Weeks) – 1.5 Points
  • History of DVT/PE – 1.5 Points
  • Hemoptysis – 1 Point
  • Malignancy – 1 Point
• “Traditional” Wells Interpretation:
  • > 6: High Probability
  • 2-5: Moderate Probability
  • 0-1: Low Probability
• “Modified” Wells Interpretation:
  • > 4: PE Likely
  • ≤ 4: PE Unlikely

Diagnosis

• Dx: CT Pulmonary Angiogram (Gold Standard)
  • If Inconclusive or Not Available Consider Ventilation-Perfusion Scan
  • Low-Moderate Probability: Consider D-Dimer First
    • PE Likely Excluded if D-Dimer < 500 ng/mL & Would Not Need CT
  • If Unstable & High Clinical Probability: Empirically Treat Before Definitive Diagnosis
• ABG Findings:
  • Hypoxemia
  • Respiratory Alkalosis
  • Widened Alveolar-Arterial Oxygen Gradient
• Classic ECG Findings:
  • Tachycardia – Most Common EKG Finding
  • S1Q3T3 Pattern (Indicates Right Ventricle Strain) – Rarely Seen
  • T1-4 Inversion
• Echo Findings:
  • Left Ventricle – Small but Normal Systolic Function
  • Septal Flattening (RV Pressure Overload)
  • Right Ventricle – Severely Dilated with Reduced Systolic Function/Wall Hypokinesis
  • Pulmonary Artery Hypertension
  • McConnell Sign – RV Dysfunction with Akinesia of Mid-Free Wall but Normal Motion at the Apex
  • D-Sign – Left Ventricle is “D” Shaped Due to Flattening of the Interventricular Septum from Right Ventricular Overload
• D-Dimer Highly Sensitive but Not Specific

Treatment

• Stable: Anticoagulation
• Unstable & High Probability: Systemic Thrombolytics
  • If Contraindicated: Embolectomy (Surgical or Endovascular)