FLARE: Novel treatment safe, effective in acute PE

SAN DIEGO — Use of catheter-directed mechanical thrombectomy without thrombolytics was safe and improved right ventricular strain in intermediate-risk patients with pulmonary embolism, according to data from the FLARE study.

“This is the first trial evaluating a novel procedure in which a catheter-directed mechanical thrombectomy device is used to treat acute PE without the use of thrombolytics,” study researcher Thomas Tu, MD, from Baptist Health Louisville, Kentucky, said during a press conference at the Society for Cardiovascular Angiography and Interventions Scientific Sessions.

Among 106 patients treated with mechanical thrombectomy (FlowTriever System, Inari Medical), the primary endpoint of RV to left ventricular ratio at 48 hours after treatment was reduced by 0.39 (P < .0001), which exceeded the pretest cutoff for efficacy of 0.12. The results remained unchanged even after exclusion of patients who did not have clinical endpoints that were measurable or other statistical anomalies, according to Tu.

The median length of stay in the ICU was 1 day, although 44 of the 106 patients spent 0 days in the ICU after the procedure, and the median days to discharge was 3.

Major adverse events, defined as device-related death, major bleeding and treatment-related adverse events such as clinical deterioration, pulmonary vascular injury or cardiac injury at 48 hours, occurred in 3.8% of patients. One patient had hemoptysis and pulmonary infarction and had to be treated with lung surgery; one patient had worsening PE and was treated with surgery; one patient developed cardiogenic shock; and one patient became agitated during the procedure and had a ventricular fibrillation arrest that had to be cardioverted.

Two patients were lost to follow-up, and one patient died from any cause.

The prospective, single-arm, multicenter trial included adults with acute submassive PE with an RV/LV ratio of 0.9 on chest CT treated with the FlowTriever System. Patients with high bleeding risk were not excluded, and safety and efficacy outcomes were core-lab assessed.

“As far as the results of this procedure, clots were removed with efficacy that was very similar to surgery,” Tu said. “We also saw a range of types of clot — from very soft, acute clot to hard, chronic, rubbery clot — removed with this technique.”

Notably, there was only one bleeding event and no patients experienced intracranial hemorrhage, which is a particularly concerning complication of thrombolytic therapy, Tu said.

When compared with other trials using low- or full-dose thrombolytics, in the FLARE study, bleeding outcomes were favorable with use of the device and the reduction in RV/LV ratio was similar to those seen in catheter-directed thrombolysis trials, according to Tu.

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He noted that the data indicate that mechanical thrombectomy is safe and effective in acutely improving RV function in patients with intermediate-risk PE.

“[The treatment] potentially has the chance to reduce bleeding complications, reduce total hospital and ICU lengths of stay,” he said. “This is a powerful trial to introduce a new therapy into our armamentarium for the treatment of PE.”

Although FLARE is a feasibility study and the FlowTriever System is still under investigation, Tu said, in clinical use, it is the device of choice in patients who are at high risk for bleeding in whom clinicians would not want to treat with thrombolytics.

“I have also expanded the use in clinical practice for acute PE of the massive variety — for patients who are actively dying — and the reason why I find it to be an ideal choice is because it results in acute hemodynamic improvement faster than can be achieved with a thrombolytic infusion, so patients get better literally on the table at the time of treatment,” he told Cardiology Today’s Intervention. – by Melissa Foster

Reference:

Tu T. Late Breaking Clinical Science II. Presented at: Society for Cardiovascular Angiography and Interventions Scientific Sessions; April 25-28, 2018; San Diego.

Disclosure: The FLARE study was sponsored by Inari Medical. Tu reports no relevant financial disclosures.