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SAN DIEGO -- A pulmonary artery clot extractor was able to improve right ventricular (RV) function without the need for thrombolytics, according to researchers here.

In the prospective FLARE study, 106 intermediate-risk patients presenting with acute pulmonary embolism (PE) had RV/LV (left ventricular) ratios fall from 1.53 to 1.15 at 48 hours after mechanical thrombectomy with the FlowTriever (P<0.0001), reported Thomas Tu, MD, of Baptist Health Louisville in Kentucky, and colleagues.

This improvement held strong even in the 101 patients who did not receive lytics, he said in a presentation at the Society for Cardiovascular Angiography and Interventions annual meeting.

The FlowTriever device enters the pulmonary artery via a large-bore guide catheter, and macerates large thrombi, before an aspiration guide catheter retracts the device and thrombus together during the retrieval process. The idea is that with the clot removed, the resulting increase in lumen size leads to reduced pulmonary artery pressure and RV strain, Tu said.

Thrombectomy took 94 minutes on average and there were no device-related complications. However, Tu's group observed one death and a 3.8% rate of major adverse events, as four patients experienced a range of events including cardiogenic shock, pulmonary infarction, and respiratory arrest.

Catheter-directed mechanical thrombectomy without the use of thrombolytics, they maintained, appears "safe and effective" in patients with intermediate-risk PE. Up next will be a randomized trial to prove just that.

"The outcomes that we saw in this trial are extremely favorable because the improvement in the size and function of the RV was comparable to previous results we've seen with thrombolytic therapy," Tu said in a statement. "Our study paves the way for this novel treatment option for patients with PE and shows that we can decrease their risk of bleeding complications while potentially being just as safe and effective."

An ICU stay lasted a median of 1 day after the procedure; 44 patients didn't require an ICU stay, while there were 21 who stayed ≥3 days.

Patients were eligible for inclusion in FLARE if they had acute submassive PE with RV/LV ratios of 0.9 or higher on chest CT.

"The results of this study tell me that I can say to a symptomatic intermediate-risk PE patient with a fair amount of confidence 'You will feel better faster with the use of this device than with anticoagulation alone.' This is because the primary study endpoint has been shown to be a fairly useful surrogate for short-term symptomatic improvement," commented Jay Giri, MD, MPH, of Penn Medicine in Philadelphia, who was not involved with FLARE.

Nonetheless, it remains to be seen how FlowTriever efficacy plays out over the long term, especially when it comes to mortality and the development of chronic thromboembolic pulmonary hypertension, Giri told MedPage Today. He added that the modest size of FLARE lends it to unanswered questions regarding safety outcomes like major bleeding, pulmonary hemorrhage, and procedural cardiopulmonary decompensation.

"While I think the current study provides some useful information on a novel therapy that expands our toolbox for interventional treatment of PE, the most important question remains unanswered both by this study and prior comparable studies of other PE devices: namely, in what clinical scenarios is the risk/benefit of this device (or for that matter, any advanced therapy for PE) clearly favorable?" Giri said.

The right patients for FlowTriever therapy may be the high-risk individuals ill-suited for surgery who have bleeding contraindications, he suggested, since they have "exceedingly high mortality rates" and are in need of new aggressive options for improving short-term RV function. However, he noted that this group was not the population actually studied in the current study.

"For the field at large, studies with control groups are desperately needed in order to help clinicians target the right therapy to the right patient at the right time," Giri stated.

Russell Rosenberg, MD, and Vikas Aggarwal, MD, MPH, both of the Lewis Katz School of Medicine at Temple University in Philadelphia, likewise said that the field of PE research as a whole is lacking in appropriately-powered randomized trials.

For now, the FlowTriever appears promising and "adds another arrow in the quiver" of therapies for PE patients, but clinicians should still exercise caution and clinical judgment while taking care of them, said Rosenberg and Aggarwal.

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