Why is this study important? 

• In recent years, the management of pulmonary embolism has changed with new and multiple catheter-based options.  
• It is unknown if large-bore mechanical thrombectomy (LBMT) vs. catheter-directed thrombolysis (CDT) in the treatment of intermediate-high risk pulmonary embolism (PE) is effective and safe. 

What question was this study supposed to answer? 

The trial's goal was to compare the efficacy and safety of LBMT with CDT in the treatment of intermediate-high-risk PE. 

What did the study show? 

• Patients with intermediate-high-risk PE who were candidates for catheter-based intervention were randomized in a 1:1 fashion to undergo LBMT with the Inari FlowTriever system (n = 274) or CDT (n = 276). The CDT system used was at the institution/operator’s discretion. 
• Patients included had Main or lobar pulmonary artery embolus on echocardiography, computed tomographic (CT) pulmonary angiography, or invasive pulmonary angiography. Symptom onset ≤14 days. Systolic blood pressure (SBP) >90 mm Hg. Right ventricular (RV) dysfunction on echocardiography or CT. ≥1 additional risk factor: elevated cardiac troponin or lactate, history of heart failure or chronic lung disease, heart rate ≥110 bpm, SBP <100 mm Hg, respiratory rate ≥30 bpm, oxygen saturation <90%, syncope. 
• The primary outcome, 5-component hierarchical win ratio of all-cause mortality, intracranial hemorrhage, major bleeding, clinical deterioration/escalation to bailout, and postprocedural intensive care unit (ICU) admission and length of stay (LOS), at the sooner of hospital discharge or 7 days post-procedure for LBMT vs. CDT, was: 5.01 (95% confidence interval [CI] 3.68-6.97), p < 0.001. 

Key takeaway

The PEERLESS trial showed that in patients with intermediate-high risk PE undergoing catheter-based intervention, large-bore mechanical thrombectomy resulted in less frequent clinical deterioration and lower post-procedure ICU utilization with similar bleeding risk to catheter-directed thrombolysis.