Research Priorities in Submassive Pulmonary Embolism: Proceedings from a Multidisciplinary Research Consensus Panel

Research Consensus Panel Follow-up: 8-Year Update on Submassive Pulmonary Embolism

The 2015 Research Consensus Panel (RCP) on submassive pulmonary embolism (PE) set priorities for research in submassive PE and identified a rigorous randomized trial of catheter-directed therapy plus anticoagulation versus anticoagulation alone as the highest research priority. This update, written 8 years after the RCP was convened, describes the current state of endovascular PE practice and the Pulmonary Embolism-Thrombus Removal with Catheter-Directed Therapy trial, the main output from the RCP.

Inpatient Management of Pulmonary Embolism: Clinical Characteristics and Mortality in a High-Volume Tertiary Care Center

The optimal management strategy for submassive or intermediate risk pulmonary embolism (IRPE)-anticoagulation alone versus anticoagulation plus advanced therapies-remains in equipoise leading many institutions to create multidisciplinary PE response teams (PERTs) to guide therapy. Cause-specific mortality of IRPE has not been thoroughly examined, which is a meaningful outcome when examining the effect of specific interventions for PE. In this retrospective study, we reviewed all adult inpatient admissions between 8/1/2018 and 8/1/2019 with an encounter diagnosis of PE to study all cause and PE cause specific mortality as the primary outcomes and bleeding complications from therapies as a secondary outcome. There were 429 total inpatient admissions, of which 59.7% were IRPE. The IRPE 30-day all-cause mortality was 8.7% and PE cause-specific mortality was 0.79%. Treatment consisted of anticoagulation alone in 93.4% of cases. Advanced therapies-systemic thrombolysis, catheter directed thrombolysis, or mechanical thrombectomy, were performed in only six IRPE cases (2.3%). Decompensation of IRPE cases requiring higher level of care and/or rescue advanced therapy occurred in only five cases (2%). In-hospital major bleeding and clinically relevant non-major bleeding were more common in those receiving systemic thrombolysis (61.5%) compared to anticoagulation combined with other advanced therapies (11.7%). Despite the high overall acuity of PE cases at our institution, in-hospital all-cause mortality was low and cause-specific mortality for IRPE was rare. These data suggest the need to target other clinically meaningful outcomes when examining advanced therapies for IRPE.

Management of Acute Pulmonary Embolism

Purpose of the Review

Over 100,000 cardiovascular-related deaths annually are caused by acute pulmonary embolism (PE). While anticoagulation has historically been the foundation for treatment of PE, this review highlights the recent rapid expansion in the interventional strategies for this condition.

Recent Findings

At the time of diagnosis, appropriate risk stratification helps to accurately identify patients who may be candidates for advanced therapeutic interventions. While systemic thrombolytics (ST) is the mostly commonly utilized intervention for high-risk PE, the risk profile of ST for intermediate-risk PE limits its use. Assessment of an individualized patient risk profile, often via a multidisciplinary pulmonary response team (PERT) model, there are various interventional strategies to consider for PE management. Novel therapeutic options include catheter-directed thrombolysis, catheter-based embolectomy, or mechanical circulatory support for certain high-risk PE patients. Current data has established safety and efficacy for catheter-based treatment of PE based on surrogate outcome measures. However, there is limited long-term data or prospective comparisons between treatment modalities and ST. While PE diagnosis has improved with modern cross-sectional imaging, there is interest in improved diagnostic models for PE that incorporate artificial intelligence and machine learning techniques.

Summary

In patients with acute pulmonary embolism, after appropriate risk stratification, some intermediate and high-risk patients should be considered for interventional-based treatment for PE.

Interventional Radiology Therapy: Inferior Vena Cava Filter and Catheter-based Therapies

Endovascular management of pulmonary embolism can be divided into therapeutic and prophylactic treatments. Prophylactic treatment includes inferior vena cava filter placement, whereas endovascular therapeutic interventions include an array of catheter-directed therapies. The indications for both modalities have evolved over the last decade as new evidence has become available.

Interventional Therapies for Acute Pulmonary Embolism: Current Status and Principles for the Development of Novel Evidence: A Scientific Statement From the American Heart Association

Pulmonary embolism (PE) represents the third leading cause of cardiovascular mortality. The technological landscape for management of acute intermediate- and high-risk PE is rapidly evolving. Two interventional devices using pharmacomechanical means to recanalize the pulmonary arteries have recently been cleared by the US Food and Drug Administration for marketing, and several others are in various stages of development. The purpose of this document is to clarify the current state of endovascular interventional therapy for acute PE and to provide considerations for evidence development for new devices that will define which patients with PE would derive the greatest net benefit from their use in various clinical settings. First, definitions and limitations of commonly used risk stratification tools for PE are reviewed. An adjudication of risks and benefits of available interventional therapies for PE follows. Next, considerations for optimal future evidence development in this field are presented in the context of the current US regulatory framework. Finally, the document concludes with a discussion of the pros and cons of the rapidly expanding PE response team model of care delivery.

Assessment of Right Ventricular Function in the Research Setting: Knowledge Gaps and Pathways Forward. An Official American Thoracic Society Research Statement

BACKGROUND

Right ventricular (RV) adaptation to acute and chronic pulmonary hypertensive syndromes is a significant determinant of short- and long-term outcomes. Although remarkable progress has been made in the understanding of RV function and failure since the meeting of the NIH Working Group on Cellular and Molecular Mechanisms of Right Heart Failure in 2005, significant gaps remain at many levels in the understanding of cellular and molecular mechanisms of RV responses to pressure and volume overload, in the validation of diagnostic modalities, and in the development of evidence-based therapies.

METHODS

A multidisciplinary working group of 20 international experts from the American Thoracic Society Assemblies on Pulmonary Circulation and Critical Care, as well as external content experts, reviewed the literature, identified important knowledge gaps, and provided recommendations.

RESULTS

This document reviews the knowledge in the field of RV failure, identifies and prioritizes the most pertinent research gaps, and provides a prioritized pathway for addressing these preclinical and clinical questions. The group identified knowledge gaps and research opportunities in three major topic areas: 1) optimizing the methodology to assess RV function in acute and chronic conditions in preclinical models, human studies, and clinical trials; 2) analyzing advanced RV hemodynamic parameters at rest and in response to exercise; and 3) deciphering the underlying molecular and pathogenic mechanisms of RV function and failure in diverse pulmonary hypertension syndromes.

CONCLUSIONS

This statement provides a roadmap to further advance the state of knowledge, with the ultimate goal of developing RV-targeted therapies for patients with RV failure of any etiology.

Preservation of Cardiopulmonary Function in Patients Treated with Ultrasound-Accelerated Thrombolysis in the Setting of Submassive Pulmonary Embolism

PURPOSE

To evaluate the clinical effectiveness of ultrasound-assisted thrombolysis (USAT) in resolution of right ventricular dysfunction (RVD), preservation of cardiopulmonary function, and quality of life (QoL) in patients with acute submassive pulmonary embolism (PE).

MATERIALS AND METHODS

A single-center prospective study of patients presenting with acute PE and signs of RVD, as determined by right ventricle-to-left ventricle diameter ratio (RV:LV) > 0.9 on computed tomographic angiography of the thorax, was performed. Patients underwent USAT with recombinant tissue plasminogen activator. Primary endpoints measured were RV:LV by echocardiogram at baseline presentation and at 72 hours and 90 days after treatment. Secondary endpoints were QoL scores assessed by SF-36 Health Surveys at baseline and at 90 days, cardiopulmonary exercise test (CPET) parameters at 90 days, and procedural outcomes, including response of pulmonary artery pressure (PAP) and procedural complications.

RESULTS

Twenty-five patients were treated between June 17, 2013, and September 15, 2014, with mean reduction of RV:LV by echocardiogram from 1.38 ± 0.28 at presentation to 0.92 ± 0.14 (P < .0001) at 72 hours and 0.84 ± 0.25 (P < .0001) at 90 days. SF-36 Health Survey scores demonstrated no long-term self-perceived adverse physical or mental effects as a result of PE. CPET parameters, including VO2_max, weight-adjusted VO2, VE/VCO2, and VD/VT demonstrated no pulmonary vascular impairment at 90 days. PAP significantly improved after USAT, with mean initial systolic pressure of 50.46 ± 13.98 mmHg reduced to 39.64 ± 8.66 mmHg (P = .0001). There were no deaths, recurrent venous thromboembolism, hemodynamic decompensation, or hemorrhage.

CONCLUSIONS

USAT resulted in significant reduction of RV:LV at 72 hours, which was preserved at 90 days. QoL and objective measures of cardiopulmonary function are preserved at 90 days in this population. Further studies with long-term follow-up are needed to determine the potential value of USAT for the prevention of post-PE syndrome in patients with submassive PE.

How the Results of a Randomized Trial of Catheter-Directed Thrombolysis Versus Anticoagulation alone for Submassive Pulmonary Embolism Would Affect Patient and Physician Decision Making: Report of an Online Survey

The purpose is to investigate how the outcomes of a randomized controlled trial (RCT) of catheter-directed thrombolysis (CDT) versus anticoagulation alone for acute submassive PE would affect clinical decision-making. An online survey was sent to the Pulmonary Embolism Response Team Consortium members and the North American Thrombosis Forum members. Participants rated their preference for CDT on a 5-point scale in 5 RCT outcome scenarios. In all scenarios, subjects in the CDT group walked farther at 1-year than those in the anticoagulation group. A total of 83.3% of patients and 67.1% of physicians preferred CDT (score > 3) if it improved exercise capacity and did not increase bleeding. In every scenario, patients scored CDT higher than physicians (p < 0.05 for each). Bleeding and clinical deterioration were independently associated with the mean score. Patients’ age, gender, and history of PE did not influence CDT scores (p = 0.083, p = 0.071, p = 0.257 respectively). For patients, 60% > 60 years, 65.5% < 60 years, 57.1% of men, and 66.3% of women preferred CDT across scenarios. In conclusion, the majority of respondents would choose CDT if it improves long-term exercise capacity and does not increase bleeding. Patients appear to accept a higher bleeding risk than physicians if CDT improves long-term exercise capacity.

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.

Pulmonary embolism attenuation is a potential imaging biomarker for pulmonary artery hemodynamic improvement after catheter-directed thrombolysis

This study examined the potential correlation between pulmonary embolism (PE) attenuation on computed tomography pulmonary angiography (CTPA) and pulmonary artery hemodynamic response to catheter-directed thrombolysis (CDT) in 10 patients with submassive PE. Treatment parameters, PE attenuation, clot burden, computed tomography signs of right ventricle dysfunction and right ventricular systolic pressure at echocardiography were retrospectively analyzed to determine correlation with pulmonary artery pressure improvement using Spearman correlation. A single reader, blinded to the treatment results, measured PE attenuation of all patients. There was a significant positive correlation between PE attenuation and absolute pulmonary artery pressure improvement with a Spearman correlation of 0.741, p=0.014. When attenuation was greater than or equal to the median (44.5 HU, n=5), CDT was associated with significantly better pulmonary artery pressure improvement ( p=0.037). Clot attenuation at CTPA may be a potential imaging biomarker for predicting pulmonary artery pressure improvement after CDT.

How I use catheter-directed interventional therapy to treat patients with venous thromboembolism

Patients who present with severe manifestations of acute venous thromboembolism (VTE) are at higher risk for premature death and long-term disability. In recent years, catheter-based interventional procedures have shown strong potential to improve clinical outcomes in selected VTE patients. However, physicians continue to be routinely faced with challenging decisions that pertain to the utilization of these risky and costly treatment strategies, and there is a relative paucity of published clinical trials with sufficient rigor and directness to inform clinical practice. In this article, using 3 distinct clinical scenario presentations, we draw from the available published literature describing the natural history, pathophysiology, treatments, and outcomes of VTE to illustrate the key factors that should influence clinical decision making for patients with severe manifestations of deep vein thrombosis and pulmonary embolism. The results of a recently completed pivotal multicenter randomized trial are also discussed.

Systemic Thrombolysis, Catheter-Directed Thrombolysis, and Anticoagulation for Intermediate-risk Pulmonary Embolism: A Simulation Modeling Analysis

OBJECTIVES

Decision making around the use of thrombolysis for patients with intermediate-risk (submassive) pulmonary embolism (PE) remains challenging. Studies indicate favorable clinical outcomes with systemic thrombolytics (intravenous tissue plasminogen activator [IV tPA]), but the risk of major bleeding and hemorrhagic stroke is a deterrent. Catheter-directed thrombolysis (CDT) may be a preferable strategy, as it has been shown to have a lower risk of bleeding than systemic thrombolysis. However, a three-arm randomized control study comparing IV tPA, CDT, and anticoagulation alone, with long-term follow up, would be costly and is unlikely to be performed. The aim of this study was to use decision modeling to quantitatively estimate the differences between the three strategies.

METHODS

We created an individual-level state-transition model to simulate long-term outcomes of a hypothetical patient cohort treated with IV tPA, CDT, or anticoagulation alone. Our model incorporated clinical randomized controlled trial and longitudinal study data to inform patient characteristics and outcomes specific to each study arm. The base case was a 65-year-old patient. Additionally, we utilized preliminary data published by the Pulmonary Embolism Response Team at the Massachusetts General Hospital. Variance in model inputs was addressed with deterministic and probabilistic sensitivity analyses. Our primary endpoint was quality-adjusted life-years (QALYs). Secondary endpoints included total cost and incremental cost-effectiveness ratios (ICERs).

RESULTS

Catheter-directed thrombolysis (mean, 95% confidence interval [CI] = 7.388 [7.381-7.396] QALYs) resulted in the most long-term utility for eligible patients compared to anticoagulation alone (7.352 [7.345-7.360] QALYs) or IV tPA (7.343 [7.336-7.351] QALYs). Patients receiving CDT had an elevated risk of hemorrhagic stroke in comparison to anticoagulation alone; however, patients treated with anticoagulation alone were more likely to experience recurrent PE associated adverse outcomes. Results were stable with sensitivity analyses varying age and sex. Our probabilistic sensitivity analysis assessing joint variance predicts CDT to be the most effective strategy, when measured by mean QALYs, in 98.4% of runs, while systemic thrombolysis was favored over anticoagulation alone 34.4% of the time. The ICER of CDT compared to anticoagulation was $317,042 per QALY gained.

CONCLUSION

In our model, for those eligible, CDT results in the largest number of QALYs for patients with intermediate-risk PE, although it is relatively expensive and the absolute difference in QALYs between anticoagulation alone and CDT is small. Future studies that provide data on longitudinal quality-of-life outcomes of patients treated for PE and characteristics of CDT would be beneficial to augment model inputs, inform assumptions, and validate results.

A Survey of Submassive Pulmonary Embolism Treatment Preferences among Medical and Endovascular Physicians

PURPOSE

To determine treatment preferences among endovascular and medical physicians who manage acute submassive pulmonary embolism (PE).

MATERIALS AND METHODS

From July through August 2016, 83 sites across the United States were surveyed, and 60 completed the survey. Endovascular and medical physicians were asked to rate their predilection for catheter-directed thrombolysis (CDT) on a 5-point scale and for systemic thrombolysis (ST) as "yes" or "no" in seven case scenarios of submassive PE. A CDT score ≥ 4 was considered to represent a predilection for CDT. Mean scores were used to compare CDT preferences between physicians. Percentages of physicians who preferred CDT or ST were calculated. P values < .05 were considered statistically significant.

RESULTS

Across all scenarios (numbered S1-S7) combined, endovascular physicians had a significantly higher CDT score (mean, 3.52) than medical physicians (mean, 3.01; P < .0001). Scenario-by-scenario analysis revealed that the mean CDT score was significantly higher for endovascular physicians (S1, 4.25; S2, 3.72; S3, 2.82; S4, 2.68; S5, 3.45; S6, 3.67; S7, 4.02) compared with medical physicians (S1, 3.62 [P < .001]; S2, 3.18 [P < .001]; S3, 2.45 [P = .001]; S4, 2.37 [P = .011]; S5, 2.97 [P < .001]; S6, 3.20 [P < .001]; S7, 3.53 [P < .001]). Overall, a significantly higher percentage of endovascular physicians (56.7%) indicated a predilection for CDT compared with medical physicians (37.9%; P < .001). Also, a significantly higher percentage of physicians, regardless of specialty, indicated a predilection for CDT (47.2%) than did for ST (5.3%; P < .0001).

CONCLUSIONS

Endovascular physicians exhibited a greater predilection for CDT to treat acute submassive PE compared with their medical colleagues. Endovascular and medical physicians seemed to more frequently choose CDT than ST.