The PERSEVERE Study

Inclusion Criteria: 1. Age at enrollment ≥18 years 2. Objective evidence of a proximal filling defect in at least one main or lobar pulmonary artery 3. High-risk class of acute PE 4. RV dysfunction, as defined RV/LV ratio ≥1.0 5. Willing and able to provide informed consent, or if unable, through a Legal Authorized Representative, with permitting research without prior consent as a third option (for Europe and UK sites only), provided compliance with IRB/EC approvals and adherence to regulatory, ethical and national standards Exclusion Criteria: 1. Prolonged cardiac arrest with loss of consciousness associated with neurological deficit. 2. Imaging evidence or other evidence that suggests, in the opinion of the Investigator, the patient is not appropriate for catheter-based intervention 3. Known pre-existing CTEPH, or CT signs of chronic PE that may point to pre-existing CTEPH 4. Recent stroke (\<14 days) 5. Recent cranial or spinal surgery (\<14 days) 6. Life-threatening active bleeding or hemorrhage into a critical area 7. Known intracranial tumor 8. End-stage medical condition with life expectancy \<3 months (irrespective of the severity of acute PE), as determined by the Investigator 9. Known sensitivity to radiographic contrast agents that, in the Investigator's opinion, cannot be adequately pre-treated 10. Inability to anticoagulate the patient, or known to have heparin-induced thrombocytopenia (HIT) 11. Current participation in another drug or device study that may interfere with the conduct of this trial 12. Ventricular arrhythmias refractory to treatment at the time of enrollment 13. Subject has any condition for which, in the opinion of the investigator, participation would not be in the best interest of the subject (e.g., compromise the well-being or that could prevent, limit, or confound the protocol-specified assessments), including a contraindication to use of FlowTriever System per local approved labeling 14. Subject is part of a vulnerable population (e.g., currently pregnant, breastfeeding or incarcerated) per local definitions 15. Subject was previously enrolled in this study 16. Subject has received prior thrombolytic (systemic or catheter-directed) therapy for any reason or thrombectomy (surgical or catheter-based) therapy for index PE, within 30 days prior to randomization