A Prospective, Single-Arm, Multicenter Trial of Catheter-Directed Mechanical Thrombectomy for Intermediate-Risk Acute Pulmonary Embolism: The FLARE Study

Objectives: The aim of this study was to evaluate the safety and effectiveness of percutaneous mechanical thrombectomy using the FlowTriever System (Inari Medical, Irvine, California) in a prospective trial of patients with acute intermediate-risk pulmonary embolism (PE). Background: Catheter-directed thrombolysis has been shown to improve right ventricular (RV) function in patients with PE. However, catheter-directed thrombolysis increases bleeding risk and many patients with PE have relative and absolute contraindications to thrombolysis. Methods: Patients with symptomatic, computed tomography–documented PE and RV/left ventricular (LV) ratios ≥0.9 were eligible for enrollment. The primary effectiveness endpoint was core laboratory–assessed change in RV/LV ratio. The primary safety endpoint comprised device-related death, major bleeding, treatment-related clinical deterioration, pulmonary vascular injury, or cardiac injury within 48 h of thrombectomy. Results: From April 2016 to October 2017, 106 patients were treated with the FlowTriever System at 18 U.S. sites. Two patients (1.9%) received adjunctive thrombolytics and were analyzed separately. Mean procedural time was 94 min; mean intensive care unit stay was 1.5 days. Forty-three patients (41.3%) did not require any intensive care unit stay. At 48 h post-procedure, average RV/LV ratio reduction was 0.38 (25.1%; p < 0.0001). Four patients (3.8%) experienced 6 major adverse events, with 1 patient (1.0%) experiencing major bleeding. One patient (1.0%) died, of undiagnosed breast cancer, through 30-day follow-up. Conclusions: Percutaneous mechanical thrombectomy with the FlowTriever System appears safe and effective in patients with acute intermediate-risk PE, with significant improvement in RV/LV ratio and minimal major bleeding. Potential advantages include immediate thrombus removal, absence of thrombolytic complications, and reduced need for post-procedural critical care.