FLASH: The FlowTriever system has an excellent safety profile in the treatment of pulmonary embolism

By Leah Kosyakovsky on

Key Points:

  • Mortality for acute PE remains high. While percutaneous mechanical thrombectomy has been used in patients with hemodynamic instability, safety and effectiveness data from large clinical trials are needed.
  • In the single-arm FLASH study, patients with acute lobar or main PA pulmonary embolism received the FlowTriever System (percutaneous mechanical thrombectomy), and both short-term and 6 month safety and effectiveness outcomes were assessed. This was perfomed as part of the FLASH multicenter, prospective registry enrolling up to 1,000 US and European PE patients.
  • The FlowTriever had an excellent safety profile with only 1.8% risk of MAE and all-cause mortality of 0.8% at 30 days. Additionally, FlowTriever use was associated with substantial immediate improvements in hemodynamics, sustained improvement in echocardiographic measures of RV function, and improvement in quality of life and dyspnea at 6 months relative to presentation.

The mortality for acute pulmonary embolism (PE) remains high, with a high incidence of exercise limitation at 3-6 months. Advanced therapies such as thrombectomy are generally indicated in cases of hemodynamic deterioration; however, there are limited data regarding the safety profile of these techniques as well as the potential utility in patients with large PEs without acute hemodynamic instability. In a breaking presentation at the 2022 TCT Conference today, Dr. Catalin Toma (UPMC) and his team presented their study: “Outcomes for the Full US Cohort of the FLASH FlowTriever Mechanical Thrombectomy Registry in Pulmonary Embolism,” or the FLASH study.

The FLASH study (NCT03761173) was a prospective, single-arm observational study conducted across 50 sites in the US which assessed the safety and effectiveness of the FlowTriever System (percutaneous mechanical thrombectomy) for the removal of pulmonary emboli in acute PE. The inclusion criteria comprised adults with acute PE and echo, CTPA, or angiographic evidence of proximal filling defect in a main or lobar pulmonary artery; relevant exclusions included contraindication to anticoagulation, severe contrast sensitivity, or life expectancy < 30 days.  A total of 799 patients were treated with the FlowTriever system. The mean age was 61.2 and 54% were male; 12.7% had severe pulmonary hypertension (>70 mm Hg) at the time of procedure, and the majority (76.7%) were classified as intermediate-high risk PE. 91.5% of patients had either a saddle or a bilateral PE.

The primary outcome was a composite of major adverse events (MAE) including 48-hour device mortality, major bleeding, and intraprocedural device or procedure-related adverse events, which occurred in 1.8% of the patients. All-cause mortality was  0.3% at 48 hours, 0.8% at 30 days, and 5% at 6 months; there was a 6.2% all-cause readmission rate at 30 days, of which the majority (4.8% total) were unrelated to PE treatment. While there was no direct comparison within this study, data from the contemporary PERT database has shown 10.2% 30-day all-cause mortality and 24.4% 30-day readmission for similar PE presentations. There was a substantial immediate hemodynamic response to the procedure, with a mean PA pressure reduction of 7.6 mm Hg (23% relative reduction, p <0.0001), cardiac index improvement of 0.29 L/min/m2 (18.9% relative reduction, p <0.0001), and total pulmonary vascular resistance reduction of -1.67 mm Hg x min/L (20.1% relative reduction, p <0.0001). There was also a significant 48-hour reduction in mean heart rate (101.5 vs 86.7 bpm, p<0.0001) and decrease in percent of patients requiring supplemental oxygen (89.5% vs 28.8%, p<0.0001). At 6 months, the mMRC dyspnea score was also substantially improved compared to presentation (2.2 point reduction, p<0.001) with similarly improved quality of life indices based on the PEmb QoL questionnaire. On echocardiographic assessment,  there was also significant improvement in RV/LV ratio, RVSP, and RV function at both 48 hours and latest follow-up. Lastly, the rates of long-term sequelae were low, with only 1.2% of patients developing CTEPH at 6 months and only 2.0% developing post-PE syndrome.

When discussing the clinical implications of the study at TCT, Dr. Toma stated: “In conclusion, the FLASH registry demonstrates the excellent safety profile  of the Flowtriever system in a real-world patient population. There was a 1.4% rate of bleeding and 0.4% rate of other MAEs. These are patients who…are high risk, but nevertheless mortality was…low on a 30 day visit. Most importantly, hemodynamics improved rapidly during the procedure with acute RV normalization following it, and this clinical recovery continued to 6 months…data from the ongoing PEERLESS RCT will provide important evidence regarding the safety and effectiveness of FlowTriever compared to catheter-directed thrombolysis.”