Evaluate the safety and effectiveness of percutaneous mechanical thrombectomy using the FlowTriever System in patients with acute intermediate-risk pulmonary embolism.


  • Prospective, single-arm, multicenter study: 106 patients, 18 sites
  • Follow-up at 48-hours & 30-days

Primary Endpoint

  • Effectiveness – reduction in RV/LV ratio at 48-hours
  • Safety – Composite major adverse event rate

Main Inclusion Criteria

  • CTA evidence of proximal PE
  • RV/LV ratio of ≥ 0.9; Systolic BP ≥ 90 mmHg; Stable heart rate < 130 bpm

Study Administration

  • IDE study with all appropriate controls
  • DSMB, CEC, & Independent Core Lab measurement of RV/LV ratio


The FLARE study met both its primary safety and effectiveness endpoints, showing large and rapid reduction in right heart strain with no device related major adverse events in the 106 patients enrolled.  The study also showed patients treated with FlowTriever had much shorter ICU and overall length of stay compared to previously published studies in which thrombolytic drugs were used to treat PE1.  FlowTriever is the only  thrombectomy device cleared by FDA for pulmonary embolism.



  • 0.38 (25.%) reduction in RV/LV ratio from 1.53 at baseline to 1.15 (p<0.0001)
  • Only 2 of 106 patients were given thrombolytics


  • No Device-Related Major Adverse Events
    • 3.8% Major Adverse Events (4/106): non-device related

Length of Stay:

  • Median ICU stay of 1 day (41.3% of patients did not go to the ICU)
  • Median length of stay = 3 day

FLARE Highlights


Reduction of RV/LV Ratio


Of Patients Received no Thrombolytic Drugs

Device Related Major-Adverse Events

RV/LV Ratio: an independent predictor of mortality

A blockage of the Pulmonary Arteries due to a blood clot can cause a pressure buildup in the right chambers of the heart leading to right heart strain and heart failure.  This is the primary cause of death following a Pulmonary Embolism leading many experts to remark that, although the clot is in the lungs, Pulmonary Embolism is truly a disease of the heart.

This right heart strain is measured by the ratio of right ventricular diameter vs. left ventricular diameter or RV/LV.  In a healthy heart, the left ventricle will always be larger than the right, i.e. the RV/LV ratio will always be less than 0.9.  Accordingly, any heart with a RV/LV ratio 0.9 is considered to be in right heart strain and at risk for heart failure.  At Inari, we believe all of these patients should be consulted by a right heart specialist.


An inclusion criteria of 0.9 RV/LV ratio was implemented in the FLARE trial because these patients have been proven to be at a higher risk of adverse outcomes:

  • The larger the RV/LV ratio, the higher the probability of death (for every 0.1 increase in ratio, the odds ratio for death is 1.14). (Wake N.)


FLARE in Context1

Reduction in RV/LV Ratio at 48 hours

  • FLARE (FlowTriever: 0 mg tPA) 25% 25%
  • SEATTLE II (USAT: 24 mg tPA) 24% 24%
  • Beccattini et al. (30-50 mg tPA) 24% 24%
  • Fasullo et al. (100 mg tPA) 27% 27%
  • Mi et al. (Systemic tPA) 8% 8%

Major Bleeding Rates

  • FLARE (FlowTriever: 0 mg tPA) 0.9% 0.9%
  • SEATTLE II (USAT: 24 mg tPA) 10% 10%
  • OPTALYSE (USAT: 4-24mg tPA) 4% 4%
  • Chaterjee et al. (Systemic tPA) 9.24% 9.24%
  • ICOPER  (Systemic tPA) 21.7% 21.7%


Mechanical thrombectomy with the FlowTriever System appears safe and effective for treatment of patients with acute intermediate-risk PE, with significant acute improvement in RV function and minimal bleeding complications. Further studies are needed to comparatively evaluate this therapy against other catheter-directed and pharmacological approaches.