Risk Stratification of Pulmonary Embolism
Risk stratification of PE should be performed using a two-step approach: first assess hemodynamic status to identify high-risk PE, then use validated clinical scores (PESI/sPESI) combined with imaging for right ventricular dysfunction and cardiac biomarkers (troponin, BNP/NT-proBNP) to differentiate intermediate-risk from low-risk PE in hemodynamically stable patients. 1
Step 1: Assess Hemodynamic Status
High-Risk (Massive) PE is defined by the presence of shock or persistent arterial hypotension:
- Systolic blood pressure <90 mm Hg 2, 1
- Sustained drop of ≥40 mm Hg for >15 minutes (not caused by new-onset arrhythmia, hypovolemia, or sepsis) 1
- Need for vasopressor support 2
- These patients account for approximately 5% of hospitalized PE cases with 30% mortality within 1 month 2
- Systolic BP ≤120 mm Hg and diastolic BP ≤65 mm Hg are associated with elevated risk of in-hospital death 3
Step 2: Risk Stratify Normotensive Patients
For hemodynamically stable patients (systolic BP ≥90 mm Hg), use a three-component assessment:
A. Clinical Risk Scores
Pulmonary Embolism Severity Index (PESI) uses 11 clinical variables 1:
- Age (1 point per year)
- Male sex (+10 points)
- Cancer (+30 points)
- Heart failure (+10 points)
- Chronic lung disease (+10 points)
- Heart rate >110/min (+20 points)
- Systolic BP <100 mm Hg (+30 points)
- Respiratory rate >30/min (+20 points)
- Temperature <36°C (+20 points)
- Altered mental status (+60 points)
- Oxygen saturation <90% (+20 points)
Simplified PESI (sPESI) assigns 1 point for each 4, 5:
- Age >80 years
- Cancer
- Chronic cardiopulmonary disease
- Heart rate ≥110/min
- Systolic BP <100 mm Hg
- Oxygen saturation <90%
Score interpretation:
- PESI Class I-II or sPESI = 0: Low-risk PE with <1% mortality 1
- Higher scores indicate intermediate or high risk 5
B. Right Ventricular Dysfunction Assessment
Assess RV dysfunction using echocardiography or CT pulmonary angiography 2, 1:
- RV/LV ratio >0.9 indicates RV dysfunction 2
- RV dilatation on imaging is associated with poor prognosis 2
C. Cardiac Biomarkers
Measure troponin and BNP/NT-proBNP 2, 1:
- Elevated troponin indicates RV injury and myocardial necrosis 2
- Elevated BNP/NT-proBNP indicates RV pressure overload 2
Final Risk Categories
Low-Risk PE:
- Hemodynamically stable (systolic BP ≥90 mm Hg) 1
- PESI Class I-II or sPESI = 0 4, 1
- No RV dysfunction on imaging 1
- Normal cardiac biomarkers 1
- Mortality <1% within 30 days 2, 1
- Accounts for 40-60% of hospitalized PE patients 2
Intermediate-Low Risk PE:
- Hemodynamically stable 1
- Either RV dysfunction OR elevated biomarkers (but not both) 1
- Mortality 3-15% over 7-90 days 2
Intermediate-High Risk PE:
- Hemodynamically stable 1
- BOTH RV dysfunction on imaging AND elevated cardiac biomarkers 1
- Higher mortality risk than intermediate-low 1
- Requires close monitoring for hemodynamic decompensation 1
High-Risk PE:
Alternative Pretest Probability Tools (For Suspected PE)
If PE is not yet confirmed, use these validated clinical prediction rules 4:
Wells Score (traditional interpretation) 2:
- 0-1 points: 3.6% probability (low risk)
- 2-6 points: 20.5% probability (moderate risk)
6 points: 66.7% probability (high risk)
Revised Geneva Score 2:
- 0-3 points: 7.9% probability (low risk)
- 4-10 points: 28.5% probability (moderate risk)
- 11-25 points: 73.7% probability (high risk)
Critical Pitfalls to Avoid
- Do not use D-dimer in high-risk patients—proceed directly to imaging 4
- Do not perform aggressive fluid resuscitation in high-risk PE—this worsens RV failure 5
- Do not rely solely on anatomical clot burden—functional hemodynamic consequences are more important for risk stratification 1
- Use age-adjusted D-dimer thresholds (age × 10 ng/mL for patients >50 years) to avoid false positives 4
- Recognize that PESI assesses 30-day all-cause mortality, while AHA/ESC schemes emphasize PE-related death 2