Good morning. Let’s get into it shall we?
This catheter made by Inari Medical is used for mechanical thrombectomy and was the first FDA approved mechanical thrombectomy catheter for pulmonary embolism. It’s important to note that this is a non-thrombolytic catheter (not injecting tPA). The FlowTriever removes thrombo-emboli via two methods. The first is aspiration where a syringe is attached to a three-way stopcock. When closed, the syringe is pulled back creating a negative pressure. When the catheter tip is proximal to the clot, the valve is opened and the clot is sucked into the negative pressure syringe. Second, dissecting the clot with the the catheter and opening nitrol mesh disks into the clot and manual retrieving the clot. Pretty cool.
The clinical trial for the Inari FlowTriever is called FLARE (The FlowTreiver Pulmonary Embolectomy Study), a prospective, single arm, multi-center trial. The device was studied in 106 submassive/intermediate risk PE patients in 18 centers across the US. Primary endpoint was reduction in RV to LV ratio. Those enrolled had a ≥0.9 LV/RV ratio. 48h post-procedure, average reduction in the ratio was about 0.38. Safety endpoints were device-related death, major bleeding, pulmonary vascular or cardiac injury within 48 hours of procedure. 42% of the patients did not require ICU stay and those that did stayed for about 1-day. They compare that they had less complications of bleeding and lower days of ICU stay compared to patients who received tPA. More patients and studies need to be conducted but good efficacy and safety nonetheless.
The FLAME Study (FlowTriever for Acute Massive Pulmonary Embolism) is now on-going (the first patient actually just got enrolled). This will be using the Inari FlowTriever in high -risk/massive PE patients. It is a prospective, multi-center, non-randomized trial with three arms (FlowTriever, context group, prior therapy) with primary endpoints of in-hospital all cause mortality (or 45 days), bailout (needing a 2nd additional rescue therapy), major bleeding, and clinical deteroriation. They are also under the guidance of the AHA. They are looking to enroll an estimated 250 patients. Unfortunately, my center is not one of the study locations.
This Bashir endovascular catheter is a combination of “pharmaco-mechanical expandable infusion baskets [used] for effective treatment of arterial and venous thromboembolism.” The idea is to dissect the clot so the body’s own endogenous lytics can flow through (this catheter claims to expose more of the clot than other devices) and then expand the infusion basket and then deliver a shower of exogenous tPA in the clot.
They tested the device in the First-In-Man clinical study, which enrolled 9 patients with primary endpoints of major bleeding (defined by the International Society of Thrombosis and hemostasis) within the first 72 hours of infusion initiation. They used 14 mg of r-tPA in bilateral PEs and 12 mg in unilateral PE over 8 hours. at 48 hours, there was a RV/LV ratio reduction of 37%. At 30 day follow-up there were no deaths. I believe there is now a follow up study called RESCUE looking to enroll about 250 patients with submassive PEs. Like the others, it will be a prospective, non-randomized, multi-center study. I think they also just enrolled their first patient not too long ago.
There are so many more catheters and therapies we can talk about like EKOS and Penumbra. I will write about them in another post.
What can you use this information for?
Well, if you like PEs and get a lot of PE cases in your hospital, it’s good to know what trials are taking place in your hospital. There are so many on-going studies to evaluate the safety and efficacy of these therapies and you never know you can enroll a patient. You can usually find out if there is a study when you activate PERT. At my center, some MICU and IR attendings are trial investigators. This brings up another subject I’m not sure how to approach: where to admit the submassive/massive PE patient. Most of them are admitted to our MICU and some of them to the CCU. How should we approach this? Unstable PE patients usually show evidence of RV dysfunction, which is a cardiac thing that needs echo guidance (they call our cardiology fellow for this). If most of them are sent to my CCU, this could be a paradigm shift at our hospital. Sounds political.