Clot Extraction With the FlowTriever Device in Acute Massive Pulmonary Embolism

FlowTriever System for Pulmonary Embolism: A Review of Clinical Evidence

Pulmonary embolism (PE) is a significant cause of cardiovascular mortality, and its incidence has been increasing due to the growing aging population. Systemic or catheter-directed thrombolytic treatment for PE has an increased risk of bleeding that may offset the benefit in some patients. Mechanical thrombectomy devices such as the FlowTriever System are designed to resolve vascular occlusion and correct ventilation-perfusion mismatch without the need for thrombolytic drugs. This review covers the FlowTriever system, clinical data from the FlowTriever Pulmonary Embolectomy Clinical Study, FlowTriever for Acute Massive Pulmonary Embolism, and FlowTriever All-comer Registry for Patient Safety and Hemodynamics trials, and real-world experiences, demonstrating its safety and effectiveness in treating intermediate-risk and high-risk PE. Additionally, we explore off-label uses of the FlowTriever System for various large vessel thromboses.

Percutaneous Management of High-Risk Pulmonary Embolism

Acute pulmonary embolism (PE) leads to an abrupt increase in pulmonary vascular resistance and right ventricular afterload, and when significant enough, can result in hemodynamic instability. High-risk PE is a dire cardiovascular emergency and portends a poor prognosis. Traditional therapeutic options to rapidly reduce thrombus burden like systemic thrombolysis and surgical pulmonary endarterectomy have limitations, both with regards to appropriate candidates and efficacy, and have limited data demonstrating their benefit in high-risk PE. There are growing percutaneous treatment options for acute PE that include both localized thrombolysis and mechanical embolectomy. Data for such therapies with high-risk PE are currently limited. However, given the limitations, there is an opportunity to improve outcomes, with percutaneous treatments options offering new mechanisms for clot reduction with a possible improved safety profile compared with systemic thrombolysis. Additionally, mechanical circulatory support options allow for complementary treatment for patients with persistent instability, allowing for a bridge to more definitive treatment options. As more data develop, a shift toward a percutaneous approach with mechanical circulatory support may become a preferred option for the management of high-risk PE at tertiary care centers.

Assessment of histological characteristics, imaging markers, and rt-PA susceptibility of ex vivo venous thrombi

Venous thromboembolism is a significant source of morbidity and mortality worldwide. Catheter-directed thrombolytics is the primary treatment used to relieve critical obstructions, though its efficacy varies based on the thrombus composition. Non-responsive portions of the specimen often remain in situ, which prohibits mechanistic investigation of lytic resistance or the development of diagnostic indicators for treatment outcomes. In this study, thrombus samples extracted from venous thromboembolism patients were analyzed ex vivo to determine their histological properties, susceptibility to lytic therapy, and imaging characteristics. A wide range of thrombus morphologies were observed, with a dependence on age and etymology of the specimen. Fibrinolytic inhibitors including PAI-1, alpha 2-antiplasmin, and TAFI were present in samples, which may contribute to the response venous thrombi to catheter-directed thrombolytics. Finally, a weak but significant correlation was observed between the response of the sample to lytic drug and its magnetic microstructure assessed with a quantitative MRI sequence. These findings highlight the myriad of changes in venous thrombi that may promote lytic resistance, and imaging metrics that correlate with treatment outcomes.

Mechanical thrombectomy for pulmonary embolism in patients with patent foramen Ovale

Background

The current level of evidence for mechanical thrombectomy (MT) of pulmonary embolism (PE) in patients with patent foramen ovale (PFO) is limited.

Results

This was a retrospective analysis of 9 patients with PFO and acute high-risk or intermediate-high-risk PE, 6 with intermediate-high risk and 3 with high-risk PE. All underwent MT using the Inari FlowTriever System from Dec 2018 to November 2019. Six of these patients had confirmed deep venous thrombosis. The technical and clinical success rate for MT in all patients was 100% and 77.8%, respectively. Right-heart strain improved in 6/8 patients on follow-up echocardiography. Mean main pulmonary artery (MPA) pressure significantly decreased after MT (p < 0.012). One patient presented with altered mental status (somnolence and disorientation) prior to coronary artery angiogram and thrombectomy, developed a middle cerebral artery embolic stroke 1 day after MT, and recovered with minor sequalae and later was discharged. There was no in-hospital mortality.

Conclusions

MT using FlowTriever was feasible and safe, successfully improving MPA pressure in patients presenting with concurrent PFO and PE.

Review of pulmonary emboli and techniques for their mechanical removal to inform device design

Pulmonary emboli present a significant burden of disease, with limited treatment options for some patients. Mechanical devices for pulmonary emboli removal are becoming increasingly prevalent though more work remains to be done. This paper briefly discusses the mechanical properties of pulmonary emboli, the disease state they cause, and the existing embolectomy devices. The goal of this paper is to aid the design of minimally invasive mechanical pulmonary emboli removal devices, by providing a review of this topic as well as some key design specifications.

Right Atrial and Massive Pulmonary Artery Mechanical Thrombectomy Under Echocardiography Guidance Using the FlowTriever System

Introduction

Management of clot in transit in patients with pulmonary embolism, who are candidates for percutaneous intervention, can be challenging. This is a case report of simultaneous right atrial mechanical thrombectomy under echocardiography guidance and pulmonary artery embolectomy under fluoroscopy guidance, using the recently introduced FlowTriever system (Inari Medical Inc., Irvine, CA, USA).

Report

An 88 year old female, resuscitated from cardiopulmonary arrest near the end of a total right hip arthroplasty, presented for management of suspected massive pulmonary embolism. Her right atrial thrombus was removed under transthoracic echocardiography guidance, and her pulmonary arterial thrombus was subsequently successfully treated under fluoroscopy.

Discussion

The FlowTriever system can be safely and effectively used under real time transthoracic echocardiography guidance to retrieve clot in transit from the cardiac chambers, in addition to its standard application for the pulmonary artery under fluoroscopy guidance.

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FlowTriever system is recently cleared by FDA for mechanical thrombectomy of pulmonary embolism.

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This is the first case of mechanical thrombectomy in the right atrium or ventricle under echocardiography guidance.

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The mechanical thrombectomy in the right atrium/ventricle was safe and resolved the patient's symptoms.

Safety and Efficacy of Acute Pulmonary Embolism Treated via Large-Bore Aspiration Mechanical Thrombectomy Using the Inari FlowTriever Device

PURPOSE

To report initial experience with safety and efficacy in the treatment of pulmonary embolism (PE) using the FlowTriever device.

MATERIALS AND METHODS

A single-center retrospective study was performed in all patients with acute central PE treated using the FlowTriever device between March 2018 and March 2019. A total of 46 patients were identified (massive = 8; submassive = 38), all with right ventricular (RV) strain and 26% with thrombolytic contraindications. Technical success (according to SIR reporting guidelines) and clinical success (defined as mean pulmonary artery pressure intraprocedural improvement) are reported, as are major device and procedure-related complications within 30 days after discharge.

RESULTS

Technical success was achieved in 100% of cases (n = 46). Average mean pulmonary artery pressure improved significantly from before to after the procedure for the total population (33.9 ± 8.9 mm Hg before, 27.0 ± 9.0 mm Hg after; P < .0001; 95% confidence interval [CI], 5.0-8.8), submassive cohort (34.7 ± 9.1 mm Hg before, 27.4 ± 9.2 mm Hg after; P < .0001; 95% CI, 5.2-9.5) and massive cohort (30.4 ± 6.9 mm Hg before, 25.4 ± 8.2 mm Hg after; P < .05; 95% CI:0.4-9.6). Intraprocedural reduction in mean pulmonary artery pressure was achieved in 88% (n = 37 of 42). A total of 100% of patients (n = 46 of 46) survived to hospital discharge. In total, 71% of patients (n = 27 of 38) experienced intraprocedural reduction in supplemental oxygen requirements. Two major adverse events (4.6%) included hemoptysis requiring intubation, and procedure-related blood loss requiring transfusion. No delayed procedure-related complications or deaths occurred within 30 days of hospital discharge.

CONCLUSIONS

Initial clinical experience using the FlowTriever to perform mechanical thrombectomy showed encouraging trends with respect to safety and efficacy for the treatment of acute central, massive, and submassive pulmonary embolism.

Catheter-based therapies in acute pulmonary embolism

AIMS

To provide a systematic review of catheter-based therapies of acute pulmonary embolism.

METHODS AND RESULTS

Studies published in peer-reviewed journals before February 2017 were included and categorized according to the mechanism of thrombus removal: fragmentation, rheolytic therapy, aspiration or catheter-directed thrombolysis. Strengths, challenges and the level of evidence of each device were evaluated. We found 16 different catheter-based therapies for acute PE; all but one being used off-label. The majority of procedures involve catheter-directed thrombolysis. Aspiration therapy shows promise, but limited data are available. Rheolytic therapy should be used with caution, if at all, due to the high number of associated complications.

CONCLUSIONS

Catheter-based therapies show promise as a treatment for acute PE, though evidence is lacking. Further research into the efficacy and safety of devices is needed.

Endovascular therapy for acute severe pulmonary embolism

Acute pulmonary embolism (PE) is a major public health problem and accounts for 100,000-180,000 deaths per year in the United States. Current prognostic stratification separates acute PE into massive, submassive, and low-risk by the presence or absence of sustained hypotension, RV dysfunction, and myocardial necrosis. Massive, submassive and low-risk PE have mortality rates of 25-65%, 3%, and < 1%, respectively. In this review we will focus on therapies currently available to manage acute massive and submassive PE.

Catheter-Directed Thrombolysis for Submassive Pulmonary Embolism

Acute pulmonary embolism (PE) is a leading cause of morbidity and mortality in the United States. PE associated with right ventricular strain, termed submassive or intermediate-risk PE, is associated with an increased rate of clinical deterioration and short-term mortality. Trials have demonstrated systemic thrombolytics may improve patient outcomes, but they carry a risk of major hemorrhage. Catheter-directed thrombolysis (CDT) may offer similar efficacy to and a lower risk of catastrophic hemorrhage than systemic thrombolysis. Three prospective trials have evaluated CDT for submassive PE; ULTIMA, SEATTLE II, and PERFECT. These trials provide evidence that CDT may improve radiographic efficacy endpoints in submassive PE with acceptable rates of major hemorrhage. However, the lack of clinical endpoints, long-term follow-up, and adequate sample size limit their generalizability. Future trials should be adequately powered and controlled so that the short- and long-term effectiveness and safety of CDT can be definitively determined.

Endovascular treatment of pulmonary embolism: Selective review of available techniques

Acute pulmonary embolism (PE) is the third most common cause of death in hospitalized patients. The development of sophisticated diagnostic and therapeutic modalities for PE, including endovascular therapy, affords a certain level of complexity to the treatment of patients with this important clinical entity. Furthermore, the lack of level I evidence for the safety and effectiveness of catheter directed therapy brings controversy to a promising treatment approach. In this review paper, we discuss the pathophysiology and clinical presentation of PE, review the medical and surgical treatment of the condition, and describe in detail the tools that are available for the endovascular therapy of PE, including mechanical thrombectomy, suction thrombectomy, and fibrinolytic therapy. We also review the literature available to date on these methods, and describe the function of the Pulmonary Embolism Response Team.

A Pulmonary Embolism Response Team: initial experiences and future directions

INTRODUCTION

Acute pulmonary embolism (PE) is a common cardiovascular condition resulting in significant morbidity and mortality. Consensus recommendations suggest risk stratification of patients into three main categories: high-risk or 'massive' PE, intermediate-risk or 'submassive' PE, and low-risk PE. Given the relative dearth of prospective, randomized clinical trials delineating optimal selection of the diverse medical, interventional, and surgical treatment approaches, clinical care requires a multidisciplinary expert approach to patients with PE. Areas covered: The Massachusetts General Hospital (MGH) Pulmonary Embolism Response Team (PERT) was the first of its kind to create a multidisciplinary, rapid response team for acute PE, integrated within a research and educational framework. The MGH PERT has treated more than 700 patients with PE, the majority of which are in the 'massive' or 'submassive' categories. The PERT Consortium™ was founded in 2015 as a collaborative network between the growing number of PERT programs internationally, with greater than 80 institutions participating within one year of establishment. Expert commentary: Since its advent, the PERT model has expanded throughout the United States and internationally through a collaborative institutional and research network. PERT may represent a new standard for the care of patients with acute PE.