Efficacy and Safety of Percutaneous Mechanical Thrombectomy in Pulmonary Embolism Patients Presenting to the Emergency Department: The FLARE Study

Jaber, Wissam

Background
The FLARE Study was a multicenter, single arm trial that demonstrated effectiveness of the FlowTriever percutaneous pulmonary embolectomy system in reducing Right Ventricle/Left Ventricle (RV/LV) ratio in patients with acute intermediate-risk pulmonary embolism (PE). Patients diagnosed in the emergency department (ED) with acute PE may have a different presentation and hospital course from those diagnosed in an in-hospital setting. The goal of this FLARE substudy is to evaluate the safety and effectiveness of percutaneous mechanical thrombectomy in patients presenting to the ED with acute intermediate-risk PE.

Methods
ED patients with acute PE and RV/LV ratio ≥ 0.9 enrolled in the FLARE study were analyzed. The primary efficacy endpoint was the change in RV/LV ratio from pre-procedure to 48-hours after. A secondary analysis examined the change in RV/LV ratio of patients with non-elevated cardiac troponin (cTn) and zero simplified PE Severity Index (sPESI) score (normal cTn-sPESI: intermediate-low risk.) The primary safety endpoints were the rate of major adverse events (MAEs: major bleeding device-related death and treatment related clinical deterioration, pulmonary vascular injury, or cardiac injury).

Results
76 ED patients were included. 39 had a sPESI score of ≥1 and 32 patients had elevated cTn. The median pre-procedure RV/LV ratio for all ED patients was 1.50 (range, 0.88 – 2.52); the difference between the pre-procedure and the 48 hours RV/LV ratio was -0.37 (p<0.001.) 3 patients (3.9%) experienced MAEs. 17 patients (22.4%) presented in the ED with normal cTn-sPESI. The median pre-procedure RV/LV ratio for this group was 1.37 (0.97 – 2.30), with a difference between the pre-procedure and the 48 hours RV/LV ratio of -0.27 (p<0.001.)

Conclusions
Patients presenting to the ED with intermediate-risk PE show significant improvement in their RV/LV ratio and low complication rates when treated with mechanical thrombectomy. Approximately a quarter of these cases in the FLARE trial had negative cTn levels and sPESI scores of zero but presented with elevated RV/LV ratios that improved post thrombectomy.