How It Works
The FlowTriever System and the ClotTriever System (Inari Medical, Irvine, California) are two mechanical thrombectomy devices designed to treat blood clotting events such as pulmonary embolism and deep vein thrombosis.1,2 Specifically, the FlowTriever is a single-use mechanical thrombectomy device indicated for the percutaneous removal of emboli and thrombi from blood vessels and is intended to treat pulmonary embolism.3 The ClotTriever System is also a single-use endovascular device designed to remove thrombi and emboli from blood vessels but is only intended for use in the peripheral vasculature.4
The ClotTriever System is made up of the ClotTriever sheath and catheter. The sheath features a self-expanding funnel for clot removal and the catheter is made up of a coring mechanism and collection bag.1 The ClotTriever System works by inserting the ClotTriever catheter into a vein and then deploying the coring mechanism and collection bag. The coring element is pulled through the blood vessel and collects thrombi as it goes. The catheter is then removed together with the thrombi. The process can be repeated several times in a single session in order to maximize clot removal.5,6
The FlowTriever system is made up of the guiding catheter; the Triever20 — a large lumen catheter and syringe; as well as the FlowTriever catheter used for clot retrieval, which features three expanding mesh disks designed to capture clots from blood vessels and deliver them to the Triever20 for extraction.2 The FlowTriever device works by inserting the guiding catheter into a vein in the groin area and threading it to the pulmonary arteries, and then deploying the retrieval catheter. Suction is then used to remove the clot.7
Who Might Benefit?
Deep vein thrombosis and pulmonary embolism are clotting conditions. Deep vein thrombosis affects about 200,000 Canadians each year.8 Venous thromboembolism occurs when a blood clot travels to the lungs and causes a pulmonary embolism; it affects about 100,000 Canadians and causes 10,000 deaths each year.9 There is some evidence emerging that COVID-19 — the disease associated with severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2may be associated with an increased risk of these conditions.7
In some cases, such blood clotting conditions can be managed on an outpatient basis, however, more severe presentations often require more robust in-hospital treatment.10,11 There is some evidence that the FlowTriever device might be of greatest use in hospitalized patients with intermediate and high-risk pulmonary embolism (PE) for whom the risk associated with the use of thrombolysis might outweigh the benefits, These might be individuals who have experienced stroke or have recently undergone surgery and who are at increased risk of hemorrhage and pulmonary embolism, for example.12-14
Availability in Canada
The FlowTriever and ClotTriever devices have both received FDA clearance under the Premarket Notification 510(k) process.3,4 These devices are not currently approved for use in Canada and it is unclear at the time of publication whether the manufacturer plans to enter the Canadian market.
What Does It Cost?
A study that included the FlowTriever device and other devices currently used to remove blood clots estimated the cost of the FlowTriever device to be approximately US$5,040; however, it was unclear how that cost estimate was ascertained.15
The FlowTriever and ClotTriever devices are both single-use technologies3,4 (i.e., they are not reusable), which may contribute to increased health care costs. However, there may be some cost savings if the devices lead to fewer complications related to use of thrombolysis. No cost impact is expected for patients assuming that the cost of the procedure would be covered under the public health care plan as for other endovascular interventions.
According to 2017 guidance from Thrombosis Canada, current practice for treating both pulmonary embolism and deep vein thrombosis involves the use of anticoagulation drugs, or in some more severe cases intravenous thrombolysis or catheter-directed thrombolysis.10,11 The choice of treatment for pulmonary embolism is based on the Pulmonary Embolism Severity Index (PESI) and the treatment of deep vein thrombosis (DVT) also varies according to the risk of complications.10,11 Hemorrhage is the main risk of both anticoagulation drugs and thrombolysis.
What Is the Evidence?
Two published studies,13,16 one substudy,17 as well as an ongoing clinical trial18 on the FlowTriever device, were identified. The FLARE study was a manufacturer-sponsored prospective, single-arm, multi-centre trial of the FlowTriever device that enrolled 106 individuals experiencing pulmonary embolism and found a significant right-to-left ventricle diameter ratio reduction 48 hours after the device was used.13 The second study was a single, retrospective case review study of 46 cases of pulmonary embolism treated with the FlowTriever device, which reported an 88% clinical success defined as an intraprocedural decrease in mean pulmonary artery pressure.16 The sub-study reported the use of the FlowTriever device to treat patients for pulmonary embolism who were diagnosed in the emergency department.17 The authors of these studies concluded that the FlowTriever device can successfully remove blood clots, but that additional evidence about the long-term outcomes of these patients would be useful. In addition to these two studies, several abstracts19-29 and case reports describe the successful use of the device.28,30-37
One clinical registry for the ClotTriever device was identified.38 An abstract that describes how the preliminary results of the registry will be reported was also identified,39 as well as several case reports.5,6,40-45 These case reports generally indicate that the device can be used successfully in the treatment of DVT of both the arms and legs.
Ideally, robust clinical trials on the optimal treatment of DVT and pulmonary embolism would be conducted to help determine the appropriate use of the FlowTriever and ClotTriever devices. For example, a study that compared thrombectomy to standard treatments like systemic anticoagulation, intravenous thrombolysis, and catheter-directed thrombolysis in terms of clinical outcomes, safety, and long-term outcomes would be very useful.
For the FlowTriever device, the FLARE study reported that 3.8% of patients suffered a major adverse event.13 According to the study, these events were the result of the procedural process and not the device itself.13 A retrospective case review study reported two major adverse events (4.6%) including hemoptysis requiring intubation, and intraprocedural blood loss requiring transfusion.16 Thus, the risk posed by the FlowTriever device regarding bleeding events and pulmonary artery injury remains unclear.
No evidence on the safety of the ClotTriever System was identified in the literature search.
Issues to Consider
Access to Care
Mechanical thrombectomy is a procedure that requires not only specific tools but also special training for clinicians.46 In Canada, mechanical thrombectomy is used for other indications such as stroke. However, it is only available in tertiary care centres, whereas thrombolysis can be offered in a wider variety of hospitals and care centres.47,48 As a result, the availability of this procedure may depend on where an individual experiencing symptoms resides.
There is considerable innovation happening in the treatment of clotting conditions such as pulmonary embolism and venous thromboembolism. In addition to the FlowTriever and ClotTriever devices, there are other mechanical thrombectomy devices coming to market, including the Aspirex catheter (Straub Medical AG, Wangs, Switzerland), the Indigo System (Penumbra, Inc., Alameda, California), Aspire Max 7 mechanical thrombectomy system (Control Medical Technology, Salt Lake City, Utah), and the AngioVac Cannula (AngioDynamics, New York).12
The FlowTriever and ClotTriever devices appear to have promising safety and effectiveness outcomes; however, more information is needed regarding when best to employ these devices so that they can be used to the greatest benefit. Additional information about the cost of these single-use devices would also help to position them in real-world practice. Robust studies comparing these new treatments to other emerging and standard treatments for venous thromboembolism are needed.
Author: Sarah Jones
- Inari Medical. ClotTriever®: extracting large clots from large vessels without the need for thrombolytics. https://www.inarimedical.com/clottriever-product-page/. Accessed 2020 Sep 21.
- Inari Medical. FlowTriever®: the first mechanical thrombectomy device indicated for pulmonary embolism. https://www.inarimedical.com/flowtriever/. Accessed 2020 Sep 16.
- U.S. Food and Drug Administration. FDA 510(k) premarket notification: FlowTriever retrieval/aspiration system 2019; https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K191710. Accessed 2020 Sep 16.
- U.S. Food and Drug Administration. FDA 510(k) premarket notification: ClotTriever thrombectormy system, ClotTriever catheter, ClotTriever sheath. 2019; https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K192332. Accessed 2020 Sep 21.
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- Srivastava A. Acute thrombolysis-resistant occlusive left femoral and iliac venous thrombosis treated with mechanical thrombectomy via the ClotTriever device. Ann Vasc Surg. 2020;65:284.e287-284.e212.
- Bellano A. New device helps Virtua treat blood clots in coronavirus patients. 2020 Aug; https://patch.com/new-jersey/gloucestertownship/new-device-helps-virtua-treat-blood-clots-coronavirus-patients. Accessed 2020 Sep 22.
- Thrombosis Canada. VTE awareness. Whitby (ON): Thrombosis Canada; 2019 https://thrombosiscanada.ca/wp-content/uploads/2019/05/Poster-C.pdf. Accessed 2020 Sep 23.
- Thrombosis Canada. C-L-O-T-S national awareness campaign. 2019 Mar; https://thrombosiscanada.ca/c-l-o-t-s-national-awareness-campaign/, 2020 Sep 23.
- Thrombosis Canada. Pulmonary Embolism (PE): treatment. Whitby (ON): Thrombosis Canada; 2017: https://thrombosiscanada.ca/wp-content/uploads/2017/07/Pulmonary-Embolism-Treatment-2017June2-Final.pdf. Accessed 2020 Sep 23.
- Thrombosis Canada. Deep Vein Thrombosis (DVT): treatment. Whitby (ON): Thrombosis Canada; 2017: https://thrombosiscanada.ca/wp-content/uploads/2017/07/Deep-Vein-Thrombosis-Treatment-2017JUL02.pdf. Accessed 2020 Sep 23.
- Maturana MA, Seitz MP, Pour-Ghaz I, Ibebuogu UN, Khouzam RN. Invasive strategies for the treatment of pulmonary embolism. Where are we in 2020? Curr Probl Cardiol. 2020:100650.
- Tu T, Toma C, Tapson VF, et al. A Prospective, single-arm, multicenter trial of catheter-directed mechanical thrombectomy for intermediate-risk acute pulmonary embolism: the FLARE study. JACC Cardiovasc Interv. 2019;12(9):859-869.
- Chauhan CA, Scolieri SK, Toma C. Percutaneous pulmonary embolectomy using the FlowTriever retrieval/aspiration system. J Vasc Interv Radiol. 2017;28(4):621-623.
- Avgerinos E, Ali AA, Toma C, et al. Catheter-directed thrombolysis versus suction thrombectomy in the management of acute pulmonary embolism. J Vasc Surg. 2018;67(2):e28.
- Wible BC, Buckley JR, Cho KH, Bunte MC, Saucier NA, Borsa JJ. Safety and efficacy of acute pulmonary embolism treated via large-bore aspiration mechanical thrombectomy using the Inari FlowTriever device. J Vasc Interv Radiol. 2019;30(9):1370-1375.
- Jaber WA, Kabrhel C, Rosenfield K, Tu T, Ouriel K, Tapson VF. Percutaneous thrombectomy in emergency department patients with pulmonary embolism: The FLARE ED sub-study. J Emerg Med. 2020;58(2):175-182.
- Inari Medical. NCT03761173: FlowTriever All-Comer Registry for Patient Safety and Hemodynamics (FLASH). ClinicalTrials.gov. Bethesda (MD): U.S. National Library of Medicine; 2019 Aug: https://clinicaltrials.gov/ct2/show/NCT03761173. Accessed 2020 Sep 21.
- Buchan A, Scott-Kirchen L, Kocurek E, et al. Abstract no. 258: Outcomes of mechanical thrombectomy using the Inari FlowTriever system for the treatment of acute pulmonary embolism. J Vasc Interv Radiol. 2020;31(Suppl 3):S116.
- Buckley J, Wible B. Abstract no. 261: Surviving pulmonary embolism: in-hospital outcomes of pulmonary embolism treated with mechanical thrombectomy versus systemic anticoagulation. J Vasc Interv Radiol. 2020;31(Suppl 3):S117.
- Buckley J, Wible B, Cho K, Saucier N, Borsa J. Abstract no. 156: Safety and efficacy of mechanical thrombectomy for acute central pulmonary embolism via large-bore aspiration technique. J Vasc Interv Radiol. 2019;30(Suppl 3):S72.
- Buckley J, Wible B, Cho K, Saucier N, Borsa J. Abstract no. 158: Mechanical thrombectomy via large-bore aspiration technique versus standard of care for the treatment of acute central pulmonary embolism: a comparison of short-term outcomes. J Vasc Interv Radiol. 2019;30(Suppl 3):S73.
- Jaber W, Tu TM, Kabrhel C. Efficacy and safety of percutaneous mechanical thrombectomy in pulmonary embolism patients presenting to the emergency department: the FLARE study. Catheter Cardiovasc Interv. 2019;93(Suppl 2):S81.
- Lacey MJ, Hammad T, Li J, et al. Prospective single center experience of pulmonary embolism management and outcomes in the era of pulmonary embolism response teams. J Am Coll Cardiol. 2020;75(11):1165.
- Markovitz M, Lambert N, Dawson L, Hoots G. Abstract no. 259: Safety and efficacy of the Inari FlowTriever device for mechanical thrombectomy in patients with acute submassive pulmonary embolism and contraindication to thrombolysis. J Vasc Interv Radiol. 2020;31(Suppl 3):S116.
- Rojo MR, Chauhan YM, Peden EK. IP279. Catheter interventions improve outcomes in patients with intermediate-risk pulmonary embolism. J Vasc Surg. 2019;69(6):e186.
- Shah N, Wible B, Paulisin J, et al. Management of inferior vena cava thrombosis with FlowTriever and ClotTriever systems without pharmacothrombolysis. J Vasc Surg. 2020;8(2):323.
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- Bhansali HM, Camargo AL, Ghiloni N, et al. Percutaneous retrieval of an embolized vegetation from pulmonary artery after ICD lead extraction. J Am Coll Cardiol. 2020;75(11):2629.
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- Murali N, Nezami N, Latich I, Brown J, Mojibian H. Simultaneous proximal embolic protection and inferior vena cava mechanical thrombectomy using the FlowTriever system. Diagn Interv Radiol. 2020;26(4):345-348.
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- Said A, Sayed L. Percutaneous thrombectomy of Impella-associated iliac artery thrombosis using the FlowTriever system. Clin Case Rep. 2020 Aug.
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- Inari Medical. NCT03575364: ClotTriever Outcomes (CLOUT) Registry. ClinicalTrials.gov. Bethesda (MD): U.S. National Library of Medicine; 2019 Nov: https://clinicaltrials.gov/ct2/show/NCT03575364. Accessed 2020 Oct 08.
- Wible B, Buckley J. Abstract no. 178: Initial results from mid-term follow-up of the ClotTriever Mechanical Thrombectomy System (CLOUT) Registry. J Vasc Interv Radiol. 2020;31(Suppl 3):S82.
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