What is the risk of pulmonary embolism after COVID-19 infection?

Risk of Pulmonary Embolism After COVID-19 Infection

The risk of pulmonary embolism (PE) after COVID-19 infection is substantially elevated, with rates ranging from 2.4% to 35% during hospitalization depending on disease severity, and this heightened thrombotic risk persists for at least one month post-recovery. 1, 2

Acute Phase Risk (During Active Infection)

Hospitalized Non-ICU Patients

• The cumulative incidence of symptomatic PE ranges from 2.4% to 9.2% at 14 days in hospitalized patients receiving standard thromboprophylaxis 1
• This represents a multi-fold higher risk compared to typical acutely ill medical inpatients (0.3-1.0% without prophylaxis) 1
• Even patients with mild COVID-19 symptoms can develop PE, including those who are negative by pulmonary embolism rule-out criteria 3

ICU/Critically Ill Patients

• PE incidence in ICU patients ranges dramatically from 8.1% to 35% depending on the study 1
• One study reported PE in 65 of 184 (35%) ICU patients, with an additional 25% having isolated proximal PE 1
• Another cohort found 25 of 150 (17%) ICU patients developed proximal PE 1
• The overall incidence of venous thromboembolism in severe COVID-19 pneumonia reaches up to 27% (95% CI: 17-37%) 4

Key Risk Factors

• Elevated D-dimer is the only consistently validated predictor of PE in COVID-19 patients 5
• D-dimer >6 times upper limit of normal predicts thrombotic events and poor prognosis 1, 6
• Obesity (BMI >30 kg/m²) and diabetes mellitus significantly increase PE risk 1
• Rapid respiratory deterioration should prompt consideration of PE 1

Post-Acute Phase Risk (After Recovery)

Extended Thrombotic Window

• The increased risk of venous thrombosis and PE persists for approximately one month after recovery from acute COVID-19 2
• One-year follow-up data from the VA database shows significantly increased risk of pulmonary embolism compared to uninfected controls 1
• Post-COVID-19 condition with PE predominantly affects females and those with preexisting conditions like cancer or diabetes 7

Long COVID Considerations

• Circulatory system disruption includes increased risks of deep vein thrombosis, pulmonary embolism, and bleeding events as part of long COVID syndrome 1
• The risk for thromboembolic complications in the post-acute phase is associated with the duration and severity of the hyperinflammatory state 1

Pathophysiologic Mechanisms

The heightened PE risk involves all elements of Virchow's triad 2:

• Endothelial damage and dysfunction from direct viral injury 1, 2
• Coagulation disorders with activation of inflammatory and thrombotic cascades 1, 8
• Blood flow disorders from immobilization and respiratory compromise 1, 2
• In situ pulmonary thrombosis in smaller vascular beds, not just embolic events from deep vein thrombi 8

Clinical Implications for Diagnosis

When to Suspect PE

• Consider PE with rapid respiratory deterioration and/or high D-dimer 1
• Chest pain in COVID-19 patients warrants PE evaluation even without traditional risk factors 3
• Common symptoms include breathlessness and chest pain, though symptom overlap complicates diagnosis 7

Diagnostic Approach

• CT pulmonary angiography remains the gold standard 4, 2
• Ultrasound of lower extremity venous system can evaluate for DVT 1
• Ventilation-perfusion lung scintigraphy may be useful when CT is contraindicated 2, 7
• Routine screening with Doppler ultrasound or based solely on elevated D-dimer is not recommended 4

Prevention Strategies

Universal Thromboprophylaxis

• All hospitalized COVID-19 patients should receive prophylactic anticoagulation (LMWH or UFH) unless contraindications exist 1, 4
• Absolute contraindications include active bleeding and platelet count <25 × 10⁹/L 1, 6
• Abnormal PT or APTT alone is not a contraindication to prophylaxis 1

Dose Escalation Considerations

• For critically ill patients with D-dimer >6 times ULN, consider intermediate-dose LMWH (enoxaparin 40-60 mg daily or 0.5 mg/kg twice daily) 1, 6
• Obesity (BMI >30 kg/m²) warrants intermediate-dose prophylaxis 1
• Some protocols use therapeutic anticoagulation for D-dimer >5 mg/L with low bleeding risk 6

Common Pitfalls to Avoid

• Do not dismiss PE risk in mild COVID-19: Even patients with minimal symptoms can develop PE 3
• Do not rely on clinical prediction rules: Traditional PE risk stratification tools may underperform in COVID-19 3
• Do not withhold prophylaxis based on mildly elevated coagulation parameters: Only severe abnormalities are contraindications 6
• Do not assume resolution of thrombotic risk at hospital discharge: Extended prophylaxis may be warranted given persistent risk post-recovery 2, 7
• Monitor for both thrombosis AND bleeding: Bleeding events occur later (median 11.4 days) than thrombotic events (median 7.0 days) 9