What are the guidelines for diagnosing and treating pulmonary embolism (PE)?

Guidelines for Diagnosing and Managing Pulmonary Embolism

CT pulmonary angiography (CTPA) is the first-line imaging test for diagnosing pulmonary embolism (PE) in patients with intermediate or high clinical probability, while D-dimer testing should be used to rule out PE in patients with low clinical probability. 1

Clinical Assessment and Risk Stratification

Initial Clinical Evaluation

• Use validated clinical prediction tools to assess PE probability:
  • Wells score or revised Geneva score 1
  • Age-adjusted D-dimer cutoffs should be used for patients over 50 years 1
  • In patients with low clinical probability, a negative D-dimer safely excludes PE 1

Risk Stratification

• Classify PE severity based on hemodynamic status 2:
  • High-risk PE: Shock or persistent arterial hypotension (systolic BP <90 mmHg or drop of ≥40 mmHg for >15 min)
  • Intermediate-risk PE: Signs of right ventricular dysfunction (RVD) and/or myocardial injury without hypotension
  • Low-risk PE: No RVD or myocardial injury, hemodynamically stable

Diagnostic Algorithm

Step 1: Clinical Probability Assessment

• Use Wells score or revised Geneva score to categorize patients into low, intermediate, or high probability 1
• Consider PE in patients with acute chest pain, shortness of breath, or syncope 3

Step 2: D-dimer Testing

• For low/intermediate clinical probability patients:
  • Negative D-dimer (<500 ng/mL) excludes PE without further imaging 2, 1
  • Age-adjusted D-dimer cutoffs: age × 10 ng/mL for patients >50 years 1
  • YEARS model can be used: PE is excluded in patients without clinical items and D-dimer <1000 mg/L, or in patients with one or more clinical items and D-dimer <500 mg/L 2

Step 3: Imaging

• CTPA is the first-line imaging test 2, 1:

  • Sensitivity 83%, specificity 96% 1
  • A positive CTPA showing segmental or more proximal filling defect confirms PE in patients with intermediate/high probability 2
  • A normal CTPA generally excludes PE 2

• Alternative imaging options when CTPA is contraindicated:

  • V/Q scintigraphy: A normal perfusion scan excludes PE; high-probability V/Q scan confirms PE 2
  • Lower limb compression ultrasonography: Positive proximal DVT confirms VTE and PE 2
  • Echocardiography: Essential in suspected high-risk PE with hemodynamic instability 2, 1

Treatment

Anticoagulation

• Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists for intermediate and low-risk PE 1, 3

  • Options include apixaban, rivaroxaban, edoxaban, or dabigatran 4, 5, 3
  • Apixaban dosing: 10 mg twice daily for 7 days, then 5 mg twice daily 4
  • Rivaroxaban dosing: 15 mg twice daily for 21 days, then 20 mg once daily 5

• Initial parenteral anticoagulation:

  • Low molecular weight heparin (LMWH) or fondaparinux preferred over unfractionated heparin (UFH) 1
  • Target APTT of 1.5-2.5 times control (45-75 seconds) for UFH therapy 1

• Duration of anticoagulation:

  • Minimum 3 months for all patients 1
  • Extended anticoagulation for unprovoked PE, persistent risk factors, or minor transient risk factors 1

Management of High-Risk PE

• For hemodynamically unstable patients (systolic BP <90 mmHg) 2, 1:
  • Systemic thrombolysis with alteplase 100 mg over 2 hours
  • Surgical embolectomy when thrombolysis is contraindicated or has failed
  • Percutaneous interventions as an alternative when surgical options unavailable
  • ECMO in cases of refractory circulatory collapse or cardiac arrest

Follow-up and Monitoring

• Clinical evaluation at 3-6 months after acute PE 1:
  • Assess for persistent symptoms, signs of recurrence, bleeding complications
  • Evaluate for chronic thromboembolic pulmonary hypertension (CTEPH) if persistent symptoms

Common Pitfalls to Avoid

1. Diagnostic Pitfalls:

   • Missing PE in elderly patients or those with severe cardiorespiratory disease 1
   • Over-diagnosing isolated subsegmental PE - consider radiologist consultation for these cases 1
   • Relying solely on clinical features without using validated prediction tools 6

2. Treatment Pitfalls:

   • Delaying anticoagulation while awaiting confirmatory tests in high-probability patients 1
   • Premature discontinuation of anticoagulants increases thrombotic risk 4, 5
   • Not considering extended anticoagulation in patients with unprovoked PE 1

3. Follow-up Pitfalls:

   • Losing patients to follow-up after acute PE 1
   • Not evaluating for CTEPH in patients with persistent symptoms 1

For complex cases, a multidisciplinary approach involving a PE response team (PERT) with specialists from critical care, hematology, and interventional radiology is recommended 1.