Pulmonary Embolism

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

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II. Epidemiology

  1. Incidence in United States
    1. Total Cases: 650,000 to 900,000 per year
    2. Deaths per year: 100,000 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. Massive Pulmonary Embolism: 50%
    4. Missed diagnosis in 50 to 70%

III. Precautions

  1. Even submassive Pulmonary Embolism (right heart strain) may present with underwhelming symptoms
  2. Pulmonary Embolism severity is determined by physiologic dysfunction, not by the size of clot burden
  3. Elderly patients have atypical presentations of Pulmonary Embolism
    1. See Chest Pain in Older Adults
    2. Common presentations in older adults with Pulmonary Embolism
      1. Dyspnea
      2. Syncope
    3. Variable presentations
      1. Tachycardia is often absent
    4. Uncommon presentations in older adults with Pulmonary Embolism
      1. Pleuritic Chest Pain
      2. Hemoptysis

IV. Risk Factors

  1. See Pulmonary Embolism Risk Factors

V. Symptoms

  1. Classic Triad
    1. Chest Pain (80-90%)
      1. Pleuritic Chest Pain (47-74%) due to pleural irritation
      2. Non-Pleuritic Chest Pain (14%)
    2. Cough (40-53%)
    3. Hemoptysis (13-20%)
  2. Dyspnea (75-85%)
    1. Sudden onset
  3. Apprehension or anxiety (50-65%)
  4. Syncope (5-13%)
  5. Diaphoresis (27-36%)

VI. 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

VII. Differential Diagnosis

  1. See Chest Pain Causes
  2. See Dyspnea Causes
  3. See Leg Pain Causes
  4. Acute Coronary Syndrome
  5. Left Ventricular Heart Failure
  6. Sepsis
  7. Arrhythmia
  8. Pulmonary Septic Embolism
    1. Causes include Infective Endocarditis, infected intravenous catheters, Lemierre's Syndrome
    2. Massive and submassive cases may be treated with Thrombolytics (as with massive Pulmonary Embolism)

VIII. 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. See Revised Geneva Score
  6. 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]
  7. Age related D-Dimer Cut-Offs increase over age 50 years
    1. See D-Dimer for thresholds
    2. Age >50 years old: Threshold = Age X 10 ng/ml (600 ng/ml at age 60, 700 at age 70 years old)
    3. Age >75 years old: 1000 ng/ml
  8. Pregnancy
    1. D-Dimer
      1. Interpretation of normal range varies based on Gestational Age (see D-Dimer for cut-offs)
    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 Doppler Ultrasound
  9. Cases in which Pulmonary Embolism may be excluded without D-Dimer
    1. Low Clinical Suspicion for Pulmonary Embolism AND all PERC Rule criteria negative
  10. Cases in which Pulmonary Embolism may be excluded without CT Chest Pulmonary Angiogram
    1. Low to moderate clinical suspicion and D-Dimer below threshold (see D-Dimer for thresholds)

IX. Labs

  1. Complete Blood Count
  2. Basic Chemistry Panel (chem8)
  3. Coagulation Studies (INR, PTT)
  4. 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]
  5. 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%
  6. Troponin I
    1. Increased in 25-50% of patients with moderate to large Pulmonary Embolism
    2. Related to right ventricular strain and right ventricular ischemia and necrosis
    3. Increased Troponin associated with increased mortality in PE to 16.4% (contrasted with 1.4%)
      1. Becattini (2007) Circulation 116(4):427-33 +PMID:17606843 [PubMed]
    4. Negative Troponin In acute Pulmonary Embolism is a reassuring prognostic signs
      1. Konstantinides (2002) Circulation 106(10): 1263-8 [PubMed]
  7. Brain Natriuretic Peptide (BNP) may predict prognosis
    1. BNP elevation with PE is associated with a 10% increase in mortality and 23% adverse outcome risk
      1. Binder (2005) Circulation 112(11): 1573-9 [PubMed]
    2. BNP <90 pg/ml associated with benign course
      1. Kucher (2003) Circulation 107:2545-7 [PubMed]

X. 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. Point of Care Ultrasound and Echocardiogram
    1. See Pulmonary Embolism Evaluation with Echocardiogram
    2. See Bedside Lung Ultrasound in Emergency (Blue Protocol)
    3. See Transesophageal Echocardiogram
    4. Evaluate for Pulmonary Hypertension and right ventricular dysfunction
      1. Right Ventricle width equal or greater than left ventricle width (Apical 4-Chamber View)
      2. McConnell Sign
        1. RV free wall hypokinesis with apical sparing
      3. D-Sign with acute RV dilatation
        1. Straightening of the interventricular septum or septal bowing
      4. Tricuspid annular plane systolic excursion reduced to <17 mm
      5. 60/60 Echo Sign
        1. Pulmonary acceleration time <60 ms
        2. Tricuspid regurgitation jet <60 mmHg
    5. References
      1. Shah (2021) Cereus 13(3): e13800 [PubMed]
      2. Cativo (2017) Case Rep Cardiol 2017:4309165 [PubMed]

XI. Imaging: Chest XRay

  1. Nonspecific Chest XRay changes in 85%
    1. Elevated hemidiaphragm (50%)
    2. Hampton's Hump (lung infarct)
      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

XII. Imaging: CT Chest Pulmonary Angiogram (Helical and Ultrafast, multidetector) -first-Line Diagnosis

  1. Efficacy
    1. Test Sensitivity: 83% (likely higher for central embolism than for subsegmental)
    2. Test Specificity: 93-96%
    3. Stein (2006) N Engl J Med 354(22): 2317-27 [PubMed]
  2. Other Findings on CT
    1. Right Ventricle diameter to Left Ventricle Diameter Ratio (axial views) >1.5
      1. Associated with increased risk of ICU admission and death in hemodynamically stable patients
      2. Ghaye (2006) RadioGraphics 26:23-39 [PubMed]
  3. 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

XIII. Imaging: Alternative for Diagnosis

  1. 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
  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

XIV. Imaging: Other Modalities

  1. Pulmonary Angiography
  2. 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

XV. Management

  1. See Pulmonary Embolism Management

XVI. Complications: Acute

  1. Acute Cor Pulmonale (acute Pulmonary Hypertension)
  2. Massive Pulmonary Embolism
    1. Systemic Hypotension and shock (or Cardiac Arrest)
      1. Systolic Blood Pressure <90 mmHg for 15 min (or Vasopressors needed)
    2. Right ventricular Heart Failure
  3. Submassive Pulmonary Embolism
    1. Right ventricular dysfunction or Heart Failure

XVII. Complications: Chronic

  1. Post-Pulmonary Embolism Syndrome (Post-PE Syndrome)
    1. Presents with persistent Shortness of Breath, Chest Pain and reduced Exercise tolerance after initial PE Management
    2. Affects 50% of PE patients at 6 months
    3. Distinguish from acute, new or breakthrough Pulmonary Embolism

XVIII. Prognosis

  1. See Troponin and BNP under labs above
  2. See Pulmonary Embolism Severity Index (PESI Score)
  3. Overall mortality
    1. Segmental or subsegmental Pulmonary Embolism: 2.6%
    2. Saddle embolism 5.4%
    3. Alkinj (2017) Mayo Clin Proc 92(10): 1511-18 [PubMed]

XIX. References

  1. Vibhakar (2015) Crit Dec Emerg Med 29(9): 2-8
  2. Wilbur (2012) Am Fam Physician 86(10):913-9 [PubMed]

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