Large-bore mechanical thrombectomy reduces poor in-hospital outcomes in PE: FLAME
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NEW ORLEANS — Compared with other treatment options and historical data, large-bore mechanical thrombectomy conferred reduced risk for in-hospital adverse clinical outcomes in high-risk patients with pulmonary embolism, data showed.
The researchers conducted the nonrandomized FLAME study, the largest interventional trial in high-risk PE, to determine whether treatment with a large-bore mechanical thrombectomy system that extracts PE thrombus without using thrombolytics (FlowTriever, Inari Medical) improved meaningful adverse in-hospital outcomes compared with a prespecified performance goal and a “context arm” of any therapy aside from FlowTriever used as primary treatment. Mitchell J. Silver, DO, FACC, FSVM, RPVI, director of the Center for Critical Limb Care and Endovascular Research at OhioHealth Heart and Vascular, presented the findings at the American College of Cardiology Scientific Session.
Data were derived from Silver MJ, et al. Clinical and Investigative Horizons. Presented at: American College of Cardiology Scientific Session; March 4-6, 2023; New Orleans (hybrid meeting).
The 90-day mortality rate in patients with high-risk PE remains at more than 25%, but a randomized trial in that population would be difficult because those patients comprise just 5% of PE cases, tend to have emergent presentation and have a high rate of combined therapies or crossover to other treatments, Silver said.
“We know that mortality is driven by right heart failure, and it’s these acute elevations in right ventricular afterload from the clot burden that is not very well tolerated ... and leads to an obstructive shock death spiral,” Silver said during the presentation. “Systemic lysis is the recommended front-line treatment, but we know there is an associated bleeding risk: 9.2% major bleeding and 1.5% intracranial hemorrhage. These rates are actually higher in this high-risk group. The reality is that less than 30% of high-risk patients receive systemic lysis because of thrombolytic contraindications and medical comorbidities. FLAME was designed on purpose to evaluate outcomes in these high-risk patients with a large-bore mechanical thrombectomy catheter compared to any other contemporary therapy.”
The primary endpoint was a composite of the following in-hospital outcomes: all-cause mortality, bailout to an alternative thrombus removal strategy, clinical deterioration and major bleeding.
The primary endpoint performance goal was 32%, established by a prior meta-analysis, and the trial was stopped after greatly exceeding the goal in a prespecified interim analysis after the first 50 patients treated with FlowTriever, Silver said.
The study included 53 patients in the FlowTriever arm (mean age, 64.8 years; 49.1% women) and 61 patients in the context arm (mean age, 61.6 years; 57.4% women).
In the context arm, the treatments were systemic thrombolytics in 68.9%, anticoagulation alone in 23%, catheter-directed thrombolytics in 6.6% and surgical thrombectomy in 1.6%, Silver said.
The primary endpoint occurred in 17% of the FlowTriever arm, beating the performance goal of 32% (P < .01), and in 63.9% of the context arm, according to the researchers.
The biggest differences between the groups were in in-hospital mortality (FlowTriever, 1.9%; performance goal, 28.5%; context arm, 29.5%) and bailout to an alternative thrombus removal strategy (FlowTriever, 3.8%; performance goal, 30.3%; context arm, 26.2%), Silver said, noting that for clinical deterioration and major bleeding, the FlowTriever arm was similar to the performance goal and better than the context arm.
Stroke occurred in 1.9% of those in the FlowTriever arm and 6.6% of those in the context arm, whereas device-related complications occurred in 22.6% of those in the FlowTriever arm and 16.4% of those in the context arm, the researchers found.
Serious adverse events occurred in 30.2% of the FlowTriever arm and 60.7% of the context arm, whereas serious adverse events related to the primary treatment device or therapy occurred in 18.9% of the FlowTriever arm and 37.7% of the context arm, Silver said, noting that most of the therapy-related serious adverse events in the context arm were related to thrombolytic therapy.
Among surviving patients, length of stay was 7 days in the FlowTriever arm and 8 days in the context arm, whereas length of ICU stay was 2 days in the FlowTriever arm and 3 days in the context arm, Silver said, noting that extracorporeal membrane oxygenation (ECMO) was used less often in the FlowTriever arm (5.7% vs. 11.5%) and patients treated with FlowTriever were more likely to be discharged home.
“Large-bore mechanical thrombectomy with FlowTriever likely reduces mortality by rapidly unloading the right ventricle, reversing the shock spiral and improving oxygenation,” Silver said during the presentation. “Care pathways for STEMI and stroke can certainly benefit patients with high-risk PE; in particular, cath lab teams that are accustomed to treating critically ill patients and have access to advanced support therapies is the ideal environment for these patients.”
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Silver MJ, et al. Clinical and Investigative Horizons. Presented at: American College of Cardiology Scientific Session; March 4-6, 2023; New Orleans (hybrid meeting).
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