FlowTriever Looks Good for Acute PE in Interim FLASH Results

The FlowTriever percutaneous mechanical thrombectomy system (Inari Medical) is safe and provides immediate benefits to patients with acute pulmonary embolism (PE), interim results of the real-world FLASH registry suggest.

Among the first 230 patients enrolled in the study, there were no deaths and only three major adverse events (all major bleeds) within the first 48 hours of the procedure, Catalin Toma, MD (University of Pittsburgh Medical Center, PA), reported during TCT Connect 2020. An access-site complication occurred in one patient.

Significant improvements in various hemodynamic measures were seen immediately after thrombectomy, with relief of dyspnea occurring within 48 hours.

“The interim results of the FLASH registry reinforce the excellent FlowTriever safety profile in 230 real-world PE patients,” he concluded, adding that the improvements in hemodynamics and dyspnea were “achieved with a short device time, with most patients not needing ICU care following the procedure. Further data will help design definitive studies in PE.”

Commenting for TCTMD, Sahil Parikh, MD (NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY), one of the moderators of the session, said the safety data—particularly the low rate of bleeding—were reassuring. “I think that the safety profile was good, and that’s a major concern in terms of using a large-bore device in a patient who’s heavily anticoagulated,” he said, noting, however, that these results came from expert sites that are well attuned to the potential risks of the procedure.

It was nice to see the rapid improvements in hemodynamics and symptom status after thrombectomy, Parikh said. “That’s really the reason you do the procedure—to get the patient out of acute trouble and expedite their recovery.”

He pointed out that the longer-term efficacy for all devices used to treat acute PE, including the FlowTriever, are not well known and that various device manufacturers are designing studies to address that gap.

A Real-world Look

Underscoring the need to find safe and effective treatment options for acute PE, Toma noted that acute mortality rates are up to 40% for high-risk (massive) PE and 15% for intermediate-risk (submassive) PE at 90 days. Advanced treatment options currently center around thrombolytic therapy, but that comes with a roughly 10% risk of major bleeding, including a 2% risk of intracerebral hemorrhage (ICH).

Optimal treatment for patients at risk of deterioration, Toma said, should carry low procedural and bleeding risks and immediately improve hemodynamics, “which could be useful in interrupting the PE death spiral, especially in patients with signs of cardiogenic shock.”

One option is the FlowTriever system, which consists of three self-expanding nitinol mesh disks designed to pluck out the clot and deliver it to a large-bore aspiration catheter for extraction; the system is meant to be used without thrombolytic therapy. It was cleared by the US Food and Drug Administration in May 2018 based on results from the FLARE investigational device exemption trial.

FLASH is a prospective, multicenter registry that will ultimately include up to 500 patients with intermediate- or high-risk PE. Toma reported data on the first 230 patients (mean age 60.7; 52.2% men) enrolled at 19 US sites. Most patients (93.0%) had intermediate-risk PE, with the minority having high-risk PE. More than two-thirds (69.7%) had concomitant deep vein thrombosis and 38.3% had a contraindication to lytics.

Procedurally, only one patient (0.4%) had an access-site complication—a clinically significant hematoma in a patient who received adjunctive thrombolytic therapy. Median device time was relatively short at 46 minutes, and average estimated blood loss was 250 mL. The median length of the hospital stay was 3.0 days, and most patients did not require a stop in the ICU.

The primary endpoint in FLASH is major adverse events—a composite of device-related mortality, major bleeding, or intraprocedural device or procedure-related adverse events, including clinical deterioration and device-related pulmonary vascular or cardiac injuries—at 48 hours. The only three events seen were major bleeds—the access-site hematoma, a significant hemoglobin drop, and an access-related bleed related to a different vascular procedure.

Thrombectomy with the FlowTriever was associated with an immediate drop in mean heart rate (113.2 to 90.5 mm Hg; P < 0.0001). The proportion of patients with tachycardia—“one of the most important clinical parameters that’s suggestive of pending hemodynamic deterioration in patients with PE,” according to Toma—fell from 77.0% to 24.6% (P < 0.001).

Various other hemodynamic parameters improved immediately as well:

• Mean pulmonary artery pressure declined from 32.0 to 25.0 mm Hg (P < 0.0001).
• Of the 43 patients with a low baseline cardiac index (< 2.0 L/min/m²), mean cardiac index increased from 1.7 to 1.9 L/min/m² (P < 0.01).
• RV stroke work index improved from 8.1 to 6.5 g/m/beat/m² (P < 0.0001).
• Total pulmonary vascular resistance, a measure of the degree of pulmonary obstruction, declined from 6.3 to 4.8 mm Hg/L/min (P < 0.0001).

The investigators also assessed dyspnea using the modified Medical Research Council scale, which ranges from 0 (dyspnea only with strenuous exercise) to 4 (too dyspneic to leave the house or breathless while dressing). The average score declined from 3.0 before thrombectomy to 1.4 at 48 hours (P < 0.0001).

Importance of Multidisciplinary Care

Taking a broad view of the field, Parikh told TCTMD that “the role of acute pulmonary embolism treatment has changed dramatically over the past decade. And as the pulmonary embolism response team, or PERT, movement has begun to take hold in hospitals and health systems across the country, it has changed the paradigm.”

All of the tools, the techniques, the devices, are best applied when there is a multidisciplinary team that can come to a consensus decision about treatment. Sahil Parikh

He stressed that the purpose of the PERT movement is not to perform more procedures. “It’s about providing comprehensive multidisciplinary care to a group of patients that had previously been getting really heterogeneous care depending upon which specialty was caring for them,” he said. “In the setting of a multidisciplinary PERT team, which is where many of these treatments belong, I think patients are selected carefully for the different types of treatment.”

Most patients are still management with anticoagulation and observation, although certain patients with high-risk features are candidates for interventions like catheter-directed thrombolysis and surgical or percutaneous embolectomy, Parikh said.

On that background, the FlowTriever system “is a nice tool in the bag,” Parikh said. “I don’t think that anyone that does this a lot [treats PE] uses the same tool in every case. I think that the type of treatment depends on the individual patient and their anatomy and the type of clot and the burden of clot. So this is a nice device for patients who have large clots [that are] relatively fresh and who have the ability to accommodate the big catheter in their vein, which is almost every patient.”

There aren’t any clear algorithms for how to choose among the various devices being employed in the treatment of acute PE, although individual high-volume centers are starting to develop their own, Parikh noted. “That’s an area of a lot of interest and I think will be an area where we really see a good deal of innovation over the coming 5 years.”

PERTs are critical when it comes to making those decisions, he stressed. “The standardization of care and the engagement of multiple disciplines we think has resulted in improved outcomes for patients. All of the tools, the techniques, the devices, are best applied when there is a multidisciplinary team that can come to a consensus decision about treatment.”