Local Ultrasound-Facilitated Thrombolysis in High-Risk Pulmonary Embolism: First Dutch Experience

Outcomes in High-Risk Pulmonary Embolism Patients Undergoing FlowTriever Mechanical Thrombectomy or Other Contemporary Therapies: Results From the FLAME Study

BACKGROUND

Hemodynamically unstable high-risk, or massive, pulmonary embolism (PE) has a reported in-hospital mortality of over 25%. Systemic thrombolysis is the guideline-recommended treatment despite limited evidence. The FLAME study (FlowTriever for Acute Massive PE) was designed to generate evidence for interventional treatments in high-risk PE.

METHODS

The FLAME study was a prospective, multicenter, nonrandomized, parallel group, observational study of high-risk PE. Eligible patients were treated with FlowTriever mechanical thrombectomy (FlowTriever Arm) or with other contemporary therapies (Context Arm). The primary end point was an in-hospital composite of all-cause mortality, bailout to an alternate thrombus removal strategy, clinical deterioration, and major bleeding. This was compared in the FlowTriever Arm to a prespecified performance goal derived from a contemporary systematic review and meta-analysis.

RESULTS

A total of 53 patients were enrolled in the FlowTriever Arm and 61 in the Context Arm. Context Arm patients were primarily treated with systemic thrombolysis (68.9%) or anticoagulation alone (23.0%). The primary end point was reached in 9/53 (17.0%) FlowTriever Arm patients, significantly lower than the 32.0% performance goal (P<0.01). The primary end point was reached in 39/61 (63.9%) Context Arm patients. In-hospital mortality occurred in 1/53 (1.9%) patients in the FlowTriever Arm and in 18/61 (29.5%) patients in the Context Arm.

CONCLUSIONS

Among patients selected for mechanical thrombectomy with the FlowTriever System, a significantly lower associated rate of in-hospital adverse clinical outcomes was observed compared with a prespecified performance goal, primarily driven by low all-cause mortality of 1.9%.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04795167.

Incidence of Mortality and Complications in High-Risk Pulmonary Embolism: A Systematic Review and Meta-Analysis

Background

The relationship between the early hemodynamic consequences of acute pulmonary embolism (PE) and short-term morbidity and mortality has long been recognized. The mortality incidence and other complications after high-risk (massive) PE, the most severe category of the disease, are summarized in this meta-analysis.

Methods

A systematic review and meta-analysis of studies reporting on patients with massive PE indexed by PubMed and the Cochrane Library over a 10-year period (2010-2020) was conducted. Studies with adequate information to specify a cohort of patients with high-risk PE defined by the American Heart Association and European Society of Cardiology criteria and their clinical outcomes were included. Incidences were calculated as weighted averages with 95% CIs.

Results

A total of 27 publications spanning 1517 patients were identified that met the search criteria for high-risk PE. In-hospital all-cause mortality averaged 28.3% (95% CI, 20.9%-37.0%) in patients at high risk, comparable to the 30-day all-cause mortality of 30.2% (95% CI, 22.3%-39.6%). In-hospital major bleeding was 13.8% (95% CI, 9.3%-20.0%), and intracranial hemorrhage was reported in 3.6% (95% CI, 2.2%-5.9%). The risk of bias in publications was graded as low-to-moderate, with substantial heterogeneity among the studies.

Conclusions

This systematic review and meta-analysis provided low-quality to moderate-quality evidence documenting mortality, major bleeding, and other complications in patients meeting the American Heart Association and European Society of Cardiology criteria for high-risk PE. This information was used to inform the design of the FLowTriever for Acute Massive Pulmonary Embolism (FLAME) study (NCT04795167), a study evaluating an advanced therapy for patients with high-risk PE.

Percutaneous Large-Bore Pulmonary Thrombectomy with the FlowTriever Device: Initial Experience in Intermediate-High and High-Risk Patients

OBJECTIVES

This retrospective cohort study investigates outcomes of patients with intermediate-high and high-risk pulmonary embolism (PE) who were treated with transfemoral mechanical thrombectomy (MT) using the large-bore Inari FlowTriever aspiration catheter system.

MATERIAL AND METHODS

Twenty-seven patients (mean age 56.1 ± 15.3 years) treated with MT for PE between 04/2021 and 11/2021 were reviewed. Risk stratification was performed according to European Society of Cardiology (ESC) guidelines. Clinical and hemodynamic characteristics before and after the procedure were compared with the paired Student's t test, and duration of hospital stay was analyzed with the Kaplan-Meier estimator. Procedure-related adverse advents were assessed.

RESULTS

Of 27 patients treated, 18 were classified as high risk. Mean right-to-left ventricular ratio on baseline CT was 1.7 ± 0.6. After MT, a statistically significant reduction in mean pulmonary artery pressures from 35.9 ± 9.6 to 26.1 ± 9.0 mmHg (p = 0.002) and heart rates from 109.4 ± 22.5 to 82.8 ± 13.8 beats per minute (p < 0.001) was achieved. Two patients died of prolonged cardiogenic shock. Three patients died of post-interventional complications of which a paradoxical embolism can be considered related to MT. One patient needed short cardiopulmonary resuscitation during the procedure due to clot displacement. Patients with PE as primary driver of clinical instability had a median intensive care unit (ICU) stay of 2 days (0.5-3.5 days). Patients who developed PE as a complication of an underlying medical condition spent 11 days (9.5-12.5 days) in the ICU.

CONCLUSION

In this small study population of predominantly high-risk PE patients, large-bore MT without adjunctive thrombolysis was feasible with an acceptable procedure-related complication rate.

EHA Guidelines on Management of Antithrombotic Treatments in Thrombocytopenic Patients With Cancer

In cancer patients, thrombocytopenia can result from bone marrow infiltration or from anticancer medications and represents an important limitation for the use of antithrombotic treatments, including anticoagulant, antiplatelet, and fibrinolytic agents. These drugs are often required for prevention or treatment of cancer-associated thrombosis or for cardioembolic prevention in atrial fibrillation in an increasingly older cancer population. Data indicate that cancer remains an independent risk factor for thrombosis even in case of thrombocytopenia, since mild-to-moderate thrombocytopenia does not protect against arterial or venous thrombosis. In addition, cancer patients are at increased risk of antithrombotic drug-associated bleeding, further complicated by thrombocytopenia and acquired hemostatic defects. Furthermore, some anticancer treatments are associated with increased thrombotic risk and may generate interactions affecting the effectiveness or safety of antithrombotic drugs. In this complex scenario, the European Hematology Association in collaboration with the European Society of Cardiology has produced this scientific document to provide a clinical practice guideline to help clinicians in the management of patients with cancer and thrombocytopenia. The Guidelines focus on adult patients with active cancer and a clear indication for anticoagulation, single or dual antiplatelet therapy, their combination, or reperfusion therapy, who have concurrent thrombocytopenia because of either malignancy or anticancer medications. The level of evidence and the strength of the recommendations were discussed according to a Delphi procedure and graded according to the Oxford Centre for Evidence-Based Medicine.

Endovascular therapies for pulmonary embolism

Purpose

The aim of this article is to define the place of new endovascular methods for the management of pulmonary embolisms (PE), on the basis of a multidisciplinary consensus.

Method and results

Briefly, from the recent literature, for high-risk PE presenting with shock or cardiac arrest, systemic thrombolysis or embolectomy is recommended, while for lowrisk PE, anticoagulation alone is proposed. Normo-tense patients with PE but with biological or imaging signs of right heart dysfunction constitute a group known as “at intermediate risk” for which the therapeutic strategy remains controversial. In fact, some patients may require more aggressive treatment in addition to the anticoagulant treatment, because approximately 10% will decompensate hemodynamically with a high risk of mortality. Systemic thrombolysis may be an option, but with hemorrhagic risks, particularly intra cranial. Various hybrid pharmacomechanical approaches are proposed to maintain the benefits of thrombolysis while reducing its risks, but the overall clinical experience of these different techniques remains limited. Patients with high intermediate and high risk pulmonary embolism should be managed by a multidisciplinary team combining the skills of cardiologists, resuscitators, pneumologists, interventional radiologists and cardiac surgeons. Such a team can determine which intervention – thrombolysis alone or assisted, percutaneous mechanical fragmentation of the thrombus or surgical embolectomy – is best suited to a particular patient.

Conclusions

This consensus document define the place of endovascular thrombectomy based on an appropriate risk stratification of PE.

Percutaneous thrombectomy in patients with massive and very high-risk submassive acute pulmonary embolism

OBJECTIVE

Examine FlowTriever thrombectomy feasibility in high-risk PE patients.

BACKGROUND

The FlowTriever thrombectomy system (Inari Medical, Irvine, CA) can reduce right ventricle (RV) strain in acute submassive pulmonary embolism (PE) patients. This technology has not been studied in higher risk PE patients.

METHODS

This multicenter retrospective analysis included patients treated with FlowTriever between 2017 and 2019 if they met at least one of the following: vasopressor dependence, PE induced respiratory failure, or decreased cardiac index (CI) measured by right heart catheterization.

RESULTS

Analysis included 34 patients: 18 massive, four intubated, 12 normotensive but with CI < 1.8. Average age was 56 and their median simplified PE severity index was 2. Patients had high bleeding risk, with 13 having recent surgery, six posttrauma, and four recent strokes. Six patients received cardiopulmonary resuscitation, and two received additional mechanical circulatory support. All patients had RV dilatation and elevated biomarkers. Clot removal was successful in 32/34 patients. CI improved from 2.0 ± 0.1 L/min/m² before thrombectomy to 2.4 ± 0.1 L/min/m² after (p = .01). The mean pulmonary artery pressure decreased from 33.2 ± 1.6 mmHg to 25.0 ± 1.5 mmHg (p = .01). The two patients-both with no or minimal thrombus removed-deteriorated during the procedure: one died and the other was successfully stabilized on ECMO. There were no other major complications. All other patients were alive at the time of data collection (mean follow-up of 205 days).

CONCLUSION

Aspiration thrombectomy appears feasible in higher risk acute PE patients with immediate hemodynamic improvement and low in-hospital mortality.

Rescue catheter-based therapies for the treatment of acute massive pulmonary embolism after unsuccessful systemic thrombolysis

The management of acute massive pulmonary embolism (PE) patients who did not respond to systemic thrombolysis (ST) has not been well established. The present study aimed to investigate the safety and effectiveness of catheter-based therapies (CDT) in this condition. We conducted a retrospective study of PE patients after unsuccessful ST (UST) between January 2012 and January 2018. Massive PE was identified in 408 patients and treated with full-dose ST therapy. Thrombolysis at 36 h was judged to be unsuccessful in 52 patients. Four ineligible patients were excluded, and the remaining 48 patients underwent rescue CDT: 30 patients underwent thrombus fragmentation with a rotating pigtail catheter; 8 patients underwent Straub rotational thrombectomy; and 10 patients underwent AngioJet rheolytic thrombectomy. In total, 42 patients subsequently underwent CDT relative to reduced-dose thrombolysis. Pooled clinical success was achieved in 45 patients, and the time-to-clinical instability relief for CDT was short (i.e., 48 h). Clinical findings significantly improved with oxygen saturation and the shock index (p < 0.01). CDT resulted in a significant decrease in the right ventricular (RV)/left ventricular end-diastolic diameter ratio and the average number of patients with pulmonary hypertension (p < 0.01). None of the patients suffered major complications or procedure-related adverse events, and two patients experienced minor complications. During follow-up, RV function symptoms were uneventful. The present study found that CDT is a safe and effective modality for rescue management of massive PE in patients with clinical instability and RV dysfunction after UST, leading to improved clinical outcomes and RV function with a low complication rate.

Adjunctive Therapy and Mortality in Patients With Unstable Pulmonary Embolism

Mortality with adjunctive therapy in patients with unstable pulmonary embolism, defined as those in shock or on ventilator support, is sparsely studied and requires further investigation. This was a retrospective cohort study based on administrative data from the Nationwide Inpatient Sample, 2016. In-hospital all-cause mortality in unstable patients with acute pulmonary embolism was assessed according to treatment. Patients were identified by International Classification of Diseases-10-Clinical Modification Codes. Most unstable patients, 85%, received only anticoagulants. Their mortality was 3,080 of 6,635 (46%) without an inferior vena cava (IVC) filter, and mortality was much less with an IVC filter, 285 of 1,185 (24%) (p <0.0001). Mortality with catheter-directed thrombolysis alone, 70 of 235 (30%), did not differ significantly from mortality with anticoagulants plus an IVC filter, p = 0.07, although a trend favored the latter. Intravenous thrombolytic therapy without an IVC filter showed a mortality of 295 of 695 (42%) which tended to be lower than mortality with anticoagulants alone (p = 0.06). The addition of an IVC filter to intravenous thrombolytic therapy resulted in a mortality of 20 of 165 (12%), which was the lowest mortality with any combination of adjunctive treatments. Intravenous thrombolytic therapy, however, was associated with more adverse effects of therapy than catheter-directed thrombolysis or anticoagulants.

Rationale for catheter-based therapies in acute pulmonary embolism

Pulmonary embolism (PE) is a common disease resulting in significant morbidity and mortality. High-risk features of PE are hypotension or shock, and early reperfusion is warranted to unload the strained right ventricle and improve clinical outcomes. Currently, systemic thrombolysis (ST) is the standard of care but is associated with bleeding complications. Catheter-based therapies (CDT) have emerged as a promising alternative having demonstrated to be equally effective while having a lower risk of bleeding. Several CDT are currently available, some combining mechanical properties with low-dose thrombolytics. Recent guidelines suggest that CDT may be considered in patients with high-risk PE who have high bleeding risk, after failed ST, or in patients with rapid haemodynamic deterioration as bail-out before ST can be effective, depending on local availability and expertise. In haemodynamically stable patients with right ventricular (RV) dysfunction (intermediate-risk PE), CDT may be considered if clinical deterioration occurs after starting anticoagulation and relative contraindications for ST due to bleeding risk exist. Decision on treatment modality should follow a risk-benefit analysis on a case by case base, weighing the risk of PE-related complications; i.e. haemodynamic deterioration vs. bleeding. As timely initiation of treatment is warranted to prevent early mortality, bleeding risk factors should be assessed at an early stage in all patients with acute PE and signs of RV dysfunction. To ensure optimal management of complex cases of PE and assess a potential CDT strategy, a multidisciplinary approach is recommended. A dedicated Pulmonary Embolism Response Team may optimize this process.