What is the role of interventional radiology in the management of acute pulmonary embolism?

Role of Interventional Radiology in Acute PE

Interventional radiology plays a critical, risk-stratified role in acute PE management, with catheter-directed therapies (CDT) serving as first-line reperfusion options for high-risk PE and selected intermediate-risk PE patients, particularly when systemic thrombolysis is contraindicated or has failed. 1

Risk-Stratified Approach to IR Intervention

High-Risk (Massive) PE

For patients with sustained hypotension (SBP <90 mmHg for ≥15 minutes) or requiring vasopressor support:

• Catheter-directed therapy is usually appropriate as initial therapy alongside anticoagulation 1
• CDT options include:
  • Pharmacomechanical thrombectomy (ultrasound-facilitated catheter-directed thrombolysis)
  • Mechanical thrombectomy alone (e.g., FlowTriever system)
  • Both approaches demonstrate rapid reduction in pulmonary artery pressure and RV/LV ratio improvement

Key evidence: The FLASH registry showed a 23% mean drop in pulmonary artery pressure (7.6 mmHg) and significant RV/LV ratio reduction (1.23→0.98) at 48 hours with mechanical thrombectomy, with favorable safety profile 1. The SEATTLE II trial demonstrated decreased thrombus burden, improved right heart strain, and reduced pulmonary hypertension with ultrasound-facilitated CDT 1.

Intermediate-Risk (Submassive) PE

For patients with RV strain (RV/LV ratio >0.9 on CTA or elevated troponin/BNP) but without hypotension:

• Catheter-directed therapy is usually appropriate as initial therapy with anticoagulation 1
• CDT provides targeted clot burden reduction and rapid RV strain relief
• Lower-dose thrombolytics can be used safely with shorter infusion durations (OPTALYSE PE trial) 1

Critical distinction: The ULTIMA trial demonstrated CDT superiority over anticoagulation alone in reversing RV dilation at 24 hours 1. The ongoing HI-PEITHO trial will provide definitive mortality and quality-of-life data 1.

Low-Risk PE

• No role for interventional radiology 1
• Anticoagulation alone is standard of care

Special Clinical Scenarios

Contraindication to Thrombolysis (e.g., Recent Intracranial Hemorrhage)

Mechanical thrombectomy without adjunctive thrombolytics is the preferred IR approach 1:

• Effectively reduces RV/LV ratio with minimized bleeding risk
• Avoids systemic or local thrombolytic administration
• ECMO may serve as bridge or stand-alone therapy but requires full anticoagulation

Right Atrial Thrombus-in-Transit

Modified treatment approach required, though specific IR techniques depend on institutional protocols 1.

Technical Considerations

The interventional radiologist can deploy:

1. Ultrasound-assisted catheter-directed thrombolysis: Direct intra-pulmonary arterial thrombolytic delivery with ultrasound acceleration
2. Mechanical thrombectomy: Large-bore aspiration systems (no thrombolytics needed)
3. Combination pharmacomechanical therapy: Synergistic approach

Important caveat: The SUNSET sPE trial found conventional multiside-hole catheters comparable to ultrasound-assisted systems in thrombus reduction at 48 hours 1, suggesting device selection may be institution-dependent.

Comparative Outcomes

CDT vs. Systemic Thrombolysis

• Systemic thrombolysis reduces mortality (OR 0.59) but increases major bleeding risk (OR 2.70) and intracranial hemorrhage 1
• CDT offers lower thrombolytic doses with targeted delivery, potentially reducing bleeding complications while maintaining efficacy 2
• Systemic thrombolysis remains underutilized outside experienced centers despite guideline recommendations 3

CDT vs. Surgical Embolectomy

• Surgical embolectomy shows higher in-hospital mortality (20% vs. 7% for CDT) 1, though this reflects selection bias toward higher-severity cases
• One meta-analysis found mechanical reperfusion (predominantly surgical) reduced mortality vs. other strategies (22.6% vs. 41.8%; OR 0.439) 1

Multidisciplinary Integration

Interventional radiologists are central members of PE Response Teams (PERT) 2, 4:

• Provide both diagnostic imaging expertise and therapeutic intervention
• Facilitate rapid decision-making for escalation of care
• Enable individualized treatment selection based on bleeding risk, hemodynamic status, and institutional resources

Common Pitfalls to Avoid

1. Delaying CDT in deteriorating intermediate-risk patients: Early intervention prevents progression to hemodynamic collapse
2. Using systemic thrombolysis when CDT available in high-bleeding-risk patients: Mechanical thrombectomy avoids thrombolytic complications
3. Applying CDT to low-risk PE: No mortality benefit, unnecessary procedural risk
4. Ignoring contraindications to anticoagulation: Even with mechanical thrombectomy, some anticoagulation is typically required

Current Evidence Gaps

Multiple randomized controlled trials are ongoing 5, 6 to definitively establish:

• Mortality benefit of CDT in intermediate-risk PE
• Optimal patient selection criteria
• Long-term quality-of-life outcomes
• Cost-effectiveness compared to anticoagulation alone

Until these trials complete, CDT remains most strongly indicated for high-risk PE and carefully selected intermediate-risk patients with evidence of clinical deterioration or high-risk features 1, 7.