How do you categorize pulmonary embolism (PE) risk as low, medium, or high risk?

Risk Stratification of Pulmonary Embolism

Pulmonary embolism (PE) should be categorized into high, intermediate, and low risk based on hemodynamic status, right ventricular dysfunction, myocardial injury markers, and validated clinical scores to guide appropriate management decisions.

High-Risk PE

• Defined by the presence of shock or persistent arterial hypotension (systolic BP <90 mmHg or a pressure drop ≥40 mmHg for >15 min not caused by new-onset arrhythmia, hypovolemia, or sepsis) 1
• Represents an immediately life-threatening emergency requiring specific management 1
• Confirmation of high-risk PE can be made with bedside echocardiography or emergency CTPA 1
• Patients with high-risk PE should receive systemic thrombolytic therapy unless contraindicated 1

Intermediate-Risk PE

Intermediate-risk PE is further stratified into two subcategories:

Intermediate-High Risk

• Normotensive patients with evidence of both RV dysfunction (on echocardiography or CTPA) AND elevated cardiac biomarkers (troponin, BNP/NT-proBNP) 1
• These patients require close monitoring for potential hemodynamic decompensation 1
• The combination of positive biomarkers and RV dysfunction on imaging is associated with a 12-fold elevation in complication risk compared to patients with low NT-proBNP 2

Intermediate-Low Risk

• Normotensive patients with either RV dysfunction OR elevated cardiac biomarkers (but not both) 1
• These patients should receive standard anticoagulation therapy while hospitalized 3

Low-Risk PE

• Hemodynamically stable patients without evidence of RV dysfunction or myocardial injury 1
• Can be identified using validated clinical prediction rules:
  • PESI Class I/II or simplified PESI (sPESI) score of 0 1
  • Absence of exclusion criteria for outpatient management 1
• These patients may be candidates for early discharge or outpatient treatment 1

Risk Assessment Algorithm

1. Initial Assessment: Evaluate for hemodynamic instability (shock, hypotension) to identify high-risk PE 1

2. For normotensive patients (non-high-risk PE):

   • Calculate clinical risk score (PESI or sPESI) 1
   • Assess for RV dysfunction using imaging (echocardiography or CTPA) 1
   • Measure cardiac biomarkers (troponin, BNP/NT-proBNP) 1

3. Risk Classification:

   • High-risk: Hemodynamic instability (shock/hypotension) 1
   • Intermediate-high risk: Normotensive with both RV dysfunction AND elevated cardiac biomarkers 1
   • Intermediate-low risk: Normotensive with either RV dysfunction OR elevated cardiac biomarkers 1
   • Low-risk: Normotensive without RV dysfunction or elevated biomarkers AND low PESI (I-II) or sPESI (0) 1

Clinical Implications of Risk Stratification

• High-risk PE: Requires immediate systemic thrombolysis or surgical embolectomy if thrombolysis is contraindicated 1
• Intermediate-high risk: Requires hospitalization with close monitoring; rescue thrombolysis if clinical deterioration occurs 1
• Intermediate-low risk: Standard anticoagulation with in-hospital observation 3
• Low-risk: Consider early discharge or outpatient treatment if appropriate support systems are in place 1

Important Considerations

• The PESI score includes: age, male sex, cancer, heart failure, chronic lung disease, heart rate >110/min, systolic BP <100 mmHg, respiratory rate >30/min, temperature <36°C, altered mental status, and oxygen saturation <90% 1
• NT-proBNP levels <1000 pg/mL have a high negative predictive value (95% for complications, 100% for death) 2
• Risk stratification should be performed concurrently with diagnosis to guide therapeutic decision-making 1
• Anatomical assessment of clot burden is less relevant for risk stratification than assessment based on functional (hemodynamic) consequences of PE 1