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Pulmonary Embolism

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Pulmonary Embolism, Pulmonary Embolus, Lung Infarction, Pulmonary Infarction, Hampton's Hump, Westermark Sign

  • Epidemiology
  1. Incidence in United States
    1. Total Cases: 250,000 to 650,000 per year
    2. Deaths per year: 200,000 per year
    3. Deaths in first hour: 11%
    4. Sudden death as presentation: 25%
  2. Mortality increases with age
    1. Age 40 years: 2.5%
    2. Age over 65 years: 40%
  3. Mortality increases if diagnosis missed
    1. Diagnosed in Emergency Department: 5% Mortality
    2. Missed Diagnosis: 30% Mortality
    3. Missed diagnosis in 50 to 70%
  • Differential Diagnosis
  • Symptoms
  1. Classic Triad
    1. Chest Pain (80-90%)
      1. Pleuritic Chest Pain (47-74%)
      2. Non-Pleuritic Chest Pain (14%)
    2. Cough (40-53%)
    3. Hemoptysis (13-20%)
  2. Dyspnea (75-85%)
  3. Apprehension or anxiety (50-65%)
  4. Syncope (5-13%)
  5. Diaphoresis (27-36%)
  • Signs
  1. Tachypnea (57-90%)
    1. Respiratory Rate over 16 (92%)
    2. Respiratory Rate over 20 (70%)
  2. Hypoxemia (<80%)
  3. Rales (50-58%)
  4. Tachycardia (26-50%)
    1. Up to two thirds of Pulmonary Embolism patients have normal sinus rhythm
  5. Fever (40%)
    1. Temperature usually 37.8 to 38.5 C
    2. Temperature rarely over 38.5 C (102.5)
  6. Gallup rhythm (34%)
  7. Phlebitis (32%)
  8. Edema (24%)
  9. Cardiac murmur (23%)
  10. Adventitious breath sounds
  11. Cyanosis (19%)
  12. Circulatory collapse (8%)
  13. Other findings inconsistently present
    1. Lower extremity swelling, tight cords, or tenderness
    2. Homan's Sign not helpful
  • Complications
  1. Acute Cor Pulmonale (Pulmonary Hypertension)
  2. Massive Pulmonary Embolism
    1. Systemic Hypotension and shock
    2. Right Heart Failure
  • Diagnosis
  1. See Pulmonary Embolism Diagnosis
  2. See Wells Clinical Prediction Rule for PE
  3. See Pulmonary Embolism Pretest Probability
  4. See Pulmonary Embolism Rule-Out Criteria (PERC Rule)
  5. At least one of three factors are present in 97% of Pulmonary Embolism
    1. Dyspnea
    2. Tachypnea
    3. Pleuritic Chest Pain
    4. Courtney (2010) Ann Emerg Med 55(4): 307-15 [PubMed]
  6. Pregnancy
    1. D-Dimer
      1. Interpretation of normal range varies based on Gestational age
    2. Ultrasound bilateral lower extremity venous doppler (or unilateral if asymmetric Leg Edema)
      1. Indicated if D-Dimer positive
      2. Anticoagulate if positive and no further testing needed (presume Pulmonary Embolism)
    3. CT Angiogram (replaces perfusion only VQ Scan, see below)
      1. Indicated for positive D-Dimer AND
      2. Negative Lower Extremity DopplerUltrasound
  • Labs
  1. D-Dimer (ELISA Test - do not use latex agglutination)
    1. Only useful in Low PE Probability patient
    2. Negative Predictive Value 99.5% if Low PE Probability
    3. Wells (2001) Ann Intern Med 135:98-107 [PubMed]
  2. Arterial Blood Gas (normal in 15% of PE patients)
    1. Normal ABG does not rule out PE
    2. Arterial pO2 low (Hypoxia)
      1. Most patients: 60-70 mmHg
      2. Twenty percent of patients: >80mmHg
      3. Five percent of patients: >90mmHg in 5%
    3. Respiratory Alkalosis
      1. Arterial pCO2 decreased in 95% of patients
    4. A-a Gradient Increased
      1. Sensitivity: 90%
      2. Sensitivity with low arterial pCO2: 98%
  3. Troponin I
    1. Increased in 25-50% of patients with moderate to large Pulmonary Embolism
    2. Related to right ventricular strain
    3. Associated with increased mortality in Pulmonary Embolism to 16.4% (contrasted with 1.4%)
      1. Becattini (2007) Circulation 116(4):427-33 +PMID:17606843 [PubMed]
  4. Brain Natriuretic Peptide (BNP) may predict prognosis
    1. BNP <90 pg/ml associated with benign course
    2. Kucher (2003) Circulation 107:2545-7 [PubMed]
  • Diagnostics
  1. Electrocardiogram
    1. See Electrocardiogram in Pulmonary Embolism
    2. See Right Ventricular Strain EKG Pattern
    3. Uncommonly shows right heart strain with S1-Q3-T3 pattern
  2. Echocardiogram
    1. Indicated in hemodynamically unstable patients
    2. Observe for Pulmonary Hypertension and right ventricular dysfunction
  1. Nonspecific Chest XRay changes in 85%
    1. Elevated hemidiaphragm (50%)
    2. Hampton's Hump
      1. Peripheral wedge shaped infiltrate or opacity at the edge of the lateral pleura
      2. Pleural based infiltrate pointed towards hilum
    3. Westermark Sign
      1. Dilated proximal vessels with a distal cutoff
      2. Marked decreased vascularity distal to a large Pulmonary Embolism
    4. Pleural Effusion
    5. Plate-like Atelectasis
  2. Excludes other Dyspnea Causes
    1. Pneumothorax
    2. Pneumomediastinum
    3. Aortic Dissection
    4. Pneumonia
  3. Normal Chest XRay in Acute Dyspnea and Hypoxemia
    1. Suggests Pulmonary Embolism if no Wheezing
  • Imaging
  • First-Line Diagnosis
  1. CT Scan (Helical and Ultrafast, multidetector)
    1. Efficacy
      1. Test Sensitivity: 83% (likely higher for central embolism than for subsegmental)
      2. Test Specificity: 96%
      3. Stein (2006) N Engl J Med 354(22): 2317-27 [PubMed]
    2. Disadvantages
      1. CT-associated Radiation Exposure (5-10 mSv)
        1. Breast tissue irradiation in younger women may be most significant risk from CT chest
      2. Difficult to use if patient severely dyspneic
        1. Patient must hold breath for 15 to 30 seconds
      3. Misses peripheral emboli
        1. However subsegmental distal peripheral emboli may be clinically insignificant
  • Imaging
  • Alternative for Diagnosis
  1. See Bedside Lung Ultrasound in Emergency (Blue Protocol)
  2. Lower Extremity Doppler (Impedance Plethysmography)
    1. Ultrasound symptomatic extremity (or consider bilateral Lower Extremity Doppler)
    2. Treatment initiated if DVT present (asymptomatic associated PE Incidence approaches 20%)
    3. Management of DVT is similar to PE and therefore confirmation of PE adds little additional value
  3. VQ Scan
    1. CT Angiogram has largely replaced VQ
    2. In the past perfusion scan only was considered in pregnancy
      1. Assumes normal baseline lungs in otherwise healthy patient (obtain Chest XRay first)
      2. However, Fetal Radiation Exposure from perfusion scan appears to exceed CT Angiogram
      3. In addition, VQ is often non-diagnostic
  • Imaging
  • Other Modalities
  1. See Pulmonary Embolism Evaluation with Echocardiogram
    1. Evaluate for Pulmonary Hypertension and right ventricular dysfunction
  2. Pulmonary Angiography
  3. Transesophageal Echo
  4. Chest MRI (No current use in PE evaluation)
    1. Efficacy
      1. 90% sensitive for proximal emboli
    2. Disadvantages
      1. 10% unable to get adequate study
    3. Indications
      1. Angiography contraindicated
      2. Pregnancy
  • Prognosis
  1. See Troponin and BNP under labs above
  2. See Pulmonary Embolism Severity Index (PESI Score)
  • References
  1. Vibhakar (2015) Crit Dec Emerg Med 29(9): 2-8
  2. Wilbur (2012) Am Fam Physician 86(10):913-9 [PubMed]