What are the criteria and guidelines for assessing and preventing pulmonary embolism (PE) risk?

Criteria and Guidelines for Assessing and Preventing Pulmonary Embolism (PE) Risk

Pulmonary embolism (PE) risk assessment should be performed using validated clinical prediction rules, with appropriate follow-up testing based on risk stratification to guide management decisions. 1, 2

Initial Risk Assessment

Clinical Prediction Rules

• Use validated clinical prediction rules to estimate pretest probability in all patients with suspected PE 1
• Either objective criteria (clinical decision rules) or gestalt clinical assessment can be used for risk stratification 1
• Common validated clinical prediction rules include:
  • Wells score (Canadian score) 1, 3
  • Geneva score and revised Geneva score 1, 4
  • Pulmonary Embolism Rule-Out Criteria (PERC) 1
  • Simplified Geneva score 4
  • Charlotte criteria 5
  • Pisa model 1

Wells Score Components

• Clinical signs of DVT (3 points)
• Alternative diagnosis less likely than PE (3 points)
• Heart rate >100 bpm (1.5 points)
• Immobilization or surgery in previous 4 weeks (1.5 points)
• Previous DVT/PE (1.5 points)
• Hemoptysis (1 point)
• Malignancy (1 point) 3

Risk Categories Based on Wells Score

• Low risk: 0-1 points (PE prevalence ~6%)
• Intermediate risk: 2-6 points (PE prevalence ~23%)
• High risk: >6 points (PE prevalence ~49%) 5
• Alternatively, can use two-level categorization: PE unlikely (≤4 points) or PE likely (>4 points) 5

Diagnostic Approach Based on Risk Stratification

Low Pretest Probability

• Apply PERC criteria for patients with low pretest probability 1
• PERC criteria include: age <50 years, heart rate <100 bpm, oxygen saturation >94%, no recent surgery/trauma, no prior venous thromboembolism, no hemoptysis, no unilateral leg swelling, and no estrogen use 1, 6
• If all PERC criteria are met, no further testing is needed (risk of PE <1%) 1
• If PERC criteria are not all met, proceed to D-dimer testing 1

Intermediate Pretest Probability

• Obtain high-sensitivity D-dimer measurement as the initial diagnostic test 1
• Use age-adjusted D-dimer thresholds (age × 10 ng/mL) for patients older than 50 years 1
• If D-dimer is negative, no further imaging is needed 1
• If D-dimer is positive, proceed to imaging (preferably CT pulmonary angiography) 1

High Pretest Probability

• Proceed directly to imaging with CT pulmonary angiography (CTPA) 1
• Reserve ventilation-perfusion (V/Q) scans for patients with contraindications to CTPA 1
• Do not obtain D-dimer measurement in patients with high pretest probability 1

Risk Stratification After PE Diagnosis

Severity Assessment

• Categorize confirmed PE into high, intermediate, and low risk based on hemodynamic status, right ventricular dysfunction, myocardial injury markers, and clinical scores 2
• High-risk PE: presence of shock or persistent arterial hypotension (systolic BP <90 mmHg or drop ≥40 mmHg for >15 min) 2
• Intermediate-risk PE: normotensive with evidence of RV dysfunction and/or elevated cardiac biomarkers 2
• Low-risk PE: hemodynamically stable without evidence of RV dysfunction or myocardial injury 2

Tools for Outpatient Management Assessment

• Pulmonary Embolism Severity Index (PESI) or simplified PESI (sPESI) should be used to identify low-risk patients suitable for outpatient management 1, 2
• Patients in PESI class I/II, sPESI 0, or meeting Hestia criteria should be considered for outpatient management 1

Exclusion Criteria for Outpatient Management

• Hemodynamic instability (HR >110 bpm, systolic BP <100 mmHg, requiring inotropes) 1
• Oxygen saturation <90% on room air 1
• Active bleeding or high risk of major bleeding 1
• Already on full-dose anticoagulation at time of PE 1
• Severe pain requiring opiates 1
• Medical comorbidities requiring hospitalization 1
• Severe renal impairment (CKD stages 4-5) or severe liver disease 1
• History of heparin-induced thrombocytopenia within the past year 1
• Social factors affecting follow-up or compliance 1

Prevention of PE

Pharmacological Prophylaxis

• Low-dose heparin prophylaxis is recommended for patients over 40 undergoing major surgery 7
• Standard prophylactic regimen: 5,000 units subcutaneously 2 hours before surgery and every 8-12 hours thereafter until fully ambulatory 7
• Contraindications to prophylaxis include bleeding disorders, neurosurgery, spinal anesthesia, eye surgery, or potentially sanguineous operations 7

Special Considerations

• Patients with cancer may require extended prophylaxis 8
• Pregnant women should receive fixed therapeutic doses of LMWH based on early pregnancy weight 8
• DOACs should not be used during pregnancy or breastfeeding 8

Follow-Up After PE

• Routine clinical evaluation 3-6 months after acute PE 8
• Consider integrated care model to ensure optimal transition from hospital to outpatient care 8
• Refer symptomatic patients with persistent perfusion defects after 3 months to specialized centers 8

Common Pitfalls to Avoid

• Overreliance on D-dimer testing in high-risk patients (high false positive rate) 1
• Failure to use age-adjusted D-dimer thresholds in older patients 1
• Neglecting to assess for outpatient management suitability in low-risk PE 1
• Focusing on anatomical clot burden rather than functional hemodynamic consequences 2
• Inadequate prophylaxis in high-risk surgical patients 7