When should the Inari FlowTriever (mechanical thrombectomy device) intervention be considered for patients with pulmonary embolism (PE)?

When to Proceed with Inari FlowTriever Intervention

The Inari FlowTriever mechanical thrombectomy should be considered primarily for hemodynamically unstable (high-risk) pulmonary embolism patients, particularly those with contraindications to thrombolysis or who have failed thrombolytic therapy, and may also be considered for selected intermediate-high risk PE patients with right ventricular dysfunction who deteriorate despite anticoagulation. 1, 2

Primary Indications for FlowTriever Intervention

High-Risk (Massive) PE - Strongest Indication

• Hemodynamically unstable PE is the clearest indication, defined as: 1, 2

  • Sustained systolic blood pressure <90 mmHg for ≥15 minutes
  • Requirement for inotropic support
  • Pulselessness or persistent profound bradycardia (heart rate <40 bpm with shock)
  • Cardiogenic shock

• When thrombolysis is contraindicated or has failed in high-risk PE patients, catheter-directed treatment including FlowTriever should be considered (Class IIa recommendation). 2

• The FLAME study demonstrated remarkable outcomes in high-risk PE patients treated with FlowTriever, with only 1.9% in-hospital mortality compared to 29.5% in patients treated with contemporary therapies (primarily systemic thrombolysis), and the composite adverse event rate was 17.0% versus 63.9%. 3

Intermediate-High Risk (Submassive) PE - Selective Use

• Rescue thrombectomy can be considered in hemodynamically stable intermediate-risk PE patients who experience clinical deterioration despite therapeutic anticoagulation. 1

• Patients must demonstrate right ventricular dysfunction (elevated RV/LV ratio on imaging) and/or evidence of myocardial injury (elevated cardiac biomarkers). 1, 4

• The FLARE study enrolled 106 intermediate-risk PE patients treated with FlowTriever, demonstrating reduction in RV/LV ratio from 1.53 to 1.15 within 48 hours, with low complication rates (1 death, minimal major bleeding). 1

Clinical Algorithm for Decision-Making

Step 1: Risk Stratification

• Assess hemodynamic stability (blood pressure, heart rate, signs of shock) 2
• Evaluate for right ventricular strain on echocardiography or CT (RV/LV ratio >0.9-1.0) 1
• Check cardiac biomarkers (troponin, BNP/NT-proBNP) 2

Step 2: Determine Bleeding Risk

• Absolute contraindications to thrombolysis favor FlowTriever: 2

  • History of hemorrhagic stroke or stroke of unknown origin
  • Ischemic stroke within 6 months
  • CNS neoplasm
  • Major trauma, surgery, or head injury within 3 weeks
  • Active bleeding

• Relative contraindications that may favor mechanical thrombectomy over thrombolysis: 2

  • Recent TIA (within 6 months)
  • Current oral anticoagulation
  • Pregnancy or first postpartum week
  • Non-compressible puncture sites

Step 3: Apply Treatment Algorithm

For High-Risk PE:

• If no contraindications to thrombolysis exist, systemic thrombolysis remains guideline-recommended first-line (Class I). 2
• However, FlowTriever should be strongly considered as primary therapy given the superior mortality outcomes in FLAME (1.9% vs 29.5%). 3
• If thrombolysis is contraindicated or fails, proceed directly to FlowTriever or surgical embolectomy. 1, 2

For Intermediate-High Risk PE:

• Initial management is anticoagulation alone (thrombolysis is Class III - not recommended for stable intermediate-risk PE). 2
• Monitor closely for clinical deterioration (worsening hypoxemia, hypotension, rising lactate, worsening RV function). 1
• If deterioration occurs despite anticoagulation, proceed to rescue FlowTriever intervention. 1, 4

Technical Considerations

• The FlowTriever system is a large-bore (24F) aspiration device that mechanically removes thrombus without requiring adjunctive thrombolytics. 1

• The device uses self-expanding nitinol disks to engage thrombus, though it can also function as a simple large-bore suction catheter. 1

• Procedural success rates approach 100% with median procedure times of 52 minutes and fluoroscopy times of 13 minutes. 5

• Pulmonary artery pressures typically decrease significantly (e.g., from 60 mmHg to 40 mmHg) immediately post-procedure. 5

Critical Pitfalls to Avoid

• Do not delay intervention in high-risk PE patients waiting for thrombolysis when contraindications exist—proceed directly to mechanical thrombectomy. 1, 3

• Do not use FlowTriever routinely in low-risk or stable intermediate-low risk PE patients—anticoagulation alone is appropriate. 2

• Ensure multidisciplinary team involvement (Pulmonary Embolism Response Team/PERT) for complex intermediate-risk cases to optimize treatment selection. 2

• Recognize that aggressive fluid resuscitation can worsen right ventricular failure—use vasopressors (norepinephrine, dobutamine) instead for hemodynamic support. 6

Institutional Requirements

• Setup of multidisciplinary teams for management of high-risk and selected intermediate-risk PE cases should be considered, depending on available resources and expertise. 1

• The FlowTriever system is FDA-cleared for use in acute PE and represents one of only two interventional devices with this specific clearance. 1