Venoarterial Extracorporeal Membrane Oxygenation for Acute Massive Pulmonary Embolism: a Meta-Analysis and Call to Action

Extracorporal Membrane Oxygenation in Massive Pulmonary Embolism

BACKGROUND

Massive pulmonary embolism (MPE) carries significant 30-day mortality risk, and a change in societal guidelines has promoted the increasing use of extracorporeal membrane oxygenation (ECMO) in the immediate management of MPE-associated cardiovascular shock. This narrative review examines the current status of ECMO in MPE.

METHODS

A literature review was performed from 1982 to 2022 searching for the terms "Pulmonary embolism" and "ECMO," and the search was refined by examining those publications that covered MPE.

RESULTS

In the patient with MPE, veno-arterial ECMO is now recommended as a bridge to interventional therapy. It can reliably decrease right ventricular overload, improve RV function, and allow hemodynamic stability and restoration of tissue oxygenation. The use of ECMO in MPE has been associated with lower mortality in registry reviews, but there has been no significant difference in outcomes between patients treated with and without ECMO in meta-analyses. Applying ECMO is also associated with substantial multisystem morbidity due to systemic inflammatory response, bleeding with coagulopathy, hemorrhagic stroke, renal dysfunction, and acute limb ischemia, which must be factored into the outcomes.

CONCLUSIONS

The application of ECMO in MPE should be combined with an aggressive interventional pulmonary interventional program and should strictly adhere to the current selection criteria.

Venoarterial Extracorporeal Life Support Use in Acute Pulmonary Embolism Shows Favorable Outcomes

BACKGROUND

Differences in outcomes by indication for venoarterial extracorporeal life support (VA-ECLS) are poorly described. We hypothesized that patients on VA-ECLS for acute pulmonary embolism (PE) have fewer complications and better survival than patients on VA-ECLS for other indications.

METHODS

All patients ≥18 years on VA-ECLS from the Extracorporeal Life Support Organization global registry (2010-2019) were evaluated (n = 29,842). After excluding patients aged >79 years (n = 729) and those with incomplete indication data (n = 2530), patients were stratified by VA-ECLS indication for PE vs all other indications. The association between being discharged alive and each type of complication with VA-ECLS indication was assessed.

RESULTS

Of 26,583 patients included in the analysis, 978 (3.7%) were on VA-ECLS for a primary diagnosis of acute PE. Acute PE patients were younger (53.1 vs 56.7 years, P < .001) and were more likely to be women (52.1% vs 32.3%, P < .001). Patients who underwent VA-ECLS for acute PE were 78% more likely to be discharged alive vs patients supported with VA-ECLS for other reasons (52.8% vs 40.4%; P < .001). Acute PE patients had fewer cardiovascular and renal complications (26.6% vs 38.0% and 31.1% vs 39.4%, respectively; adjusted P < .001). Acute PE patients had higher odds of having clots and mechanical complications (8.7% vs 7.9% and 16.7% vs 14.6%, respectively; adjusted P < .001).

CONCLUSIONS

Patients undergoing VA-ECLS for acute PE have higher odds of survival to hospital discharge compared with those supported for other indications. Additionally, VA-ECLS in this population is associated with fewer cardiovascular and renal complications but higher mechanical complications.

Role of Extracorporeal Membrane Oxygenation in the Treatment of Massive Pulmonary Embolism

Massive/high-risk pulmonary embolism (PE) is associated with a 30-day mortality rate of approximately 65%. In searching for strategies that may make a dent on this dismal mortality rate, investigators have, over the last decade, shown renewed interest in the potential beneficial role of venoarterial (V-A) extracorporeal membrane oxygenation (ECMO) in the treatment of patients with high-risk PE. There is a dearth of high-quality evidence regarding the value of ECMO in the treatment of massive PE. Studies examining this issue have generally been retrospective, often single center and frequently with small patient numbers. Moreover, these reported studies are not matched with appropriate controls, and, accordingly, it is difficult to regulate for inherent treatment bias. Not surprisingly, there are no randomized controlled trials examining the value of ECMO in the treatment of massive PE, as such trials would pose formidable feasibility challenges. Over the past several years, there has been increasing support for upfront use of V-A ECMO in the treatment of massive PE, when it is complicated by cardiac arrest. In those patients without cardiac arrest, but who have contraindications for thrombolysis, V-A ECMO combined with anticoagulation may be used to stabilize the patient. If after 3 to 5 days, such patients demonstrate persistent right ventricular dysfunction, embolectomy (either surgical or catheter based) should be performed. Well-designed, multicenter, prospective studies are urgently needed to better define the role of V-A ECMO in the treatment of patients with massive PE.

Integration of Extracorporeal Membrane Oxygenation into the Management of High-Risk Pulmonary Embolism: An Overview of Current Evidence

High-risk pulmonary embolism (PE) refers to a large embolic burden causing right ventricular failure and hemodynamic instability. It accounts for approximately 5% of all cases of PE but contributes significantly to overall PE mortality. Systemic thrombolysis is the first-line revascularization therapy in high-risk PE. Surgical embolectomy or catheter-directed therapy is recommended in patients with an absolute contraindication to systemic thrombolysis. Extracorporeal membrane oxygenation (ECMO) provides respiratory and hemodynamic support for the most critically ill PE patients with refractory cardiogenic shock or cardiac arrest. The complex management of these individuals requires urgent yet coordinated multidisciplinary care. In light of existing evidence regarding the utility of ECMO in the management of high-risk PE patients, a number of possible indications for ECMO utilization have been suggested in the literature. Specifically, in patients with refractory cardiac arrest, resuscitated cardiac arrest, or refractory shock, including in cases of failed thrombolysis, venoarterial ECMO (VA-ECMO) should be considered, either as a bridge to percutaneous or surgical embolectomy or as a bridge to recovery after surgical embolectomy. We review here the current evidence on the use of ECMO as part of the management strategy for the highest-risk presentations of PE and summarize the latest data in this indication.

Management of high-risk pulmonary embolism in the emergency department: A narrative review

BACKGROUND

High-risk pulmonary embolism (PE) is a complex, life-threatening condition, and emergency clinicians must be ready to resuscitate and rapidly pursue primary reperfusion therapy. The first-line reperfusion therapy for patients with high-risk PE is systemic thrombolytics (ST). Despite consensus guidelines, only a fraction of eligible patients receive ST for high-risk PE.

OBJECTIVE

This review provides emergency clinicians with a comprehensive overview of the current evidence regarding the management of high-risk PE with an emphasis on ST and other reperfusion therapies to address the gap between practice and guideline recommendations.

DISCUSSION

High-risk PE is defined as PE that causes hemodynamic instability. The high mortality rate and dynamic pathophysiology of high-risk PE make it challenging to manage. Initial stabilization of the decompensating patient includes vasopressor administration and supplemental oxygen or high-flow nasal cannula. Primary reperfusion therapy should be pursued for those with high-risk PE, and consensus guidelines recommend the use of ST for high-risk PE based on studies demonstrating benefit. Other options for reperfusion include surgical embolectomy and catheter directed interventions.

CONCLUSIONS

Emergency clinicians must possess an understanding of high-risk PE including the clinical assessment, pathophysiology, management of hemodynamic instability and respiratory failure, and primary reperfusion therapies.

Current status of ECMO for massive pulmonary embolism

Massive pulmonary embolism (MPE) carries significant 30-day mortality and is characterized by acute right ventricular failure, hypotension, and hypoxia, leading to cardiovascular collapse and cardiac arrest. Given the continued high mortality associated with MPE, there has been ongoing interest in utilizing extracorporeal membrane oxygenation (ECMO) to provide oxygenation support to improve hypoxia and offload the right ventricular (RV) pressure in the belief that rapid reduction of hypoxia and RV pressure will improve outcomes. Two modalities can be employed: Veno-arterial-ECMO is a reliable process to decrease RV overload and improve RV function, thus allowing for hemodynamic stability and restoration of tissue oxygenation. Veno-venous ECMO can support oxygenation but is not designed to help circulation. Several societal guidelines now suggest using ECMO in MPE with interventional therapy. There are three strategies for ECMO utilization in MPE: bridge to definitive interventional therapy, sole therapy, and recovery after interventional treatment. The use of ECMO in MPE has been associated with lower mortality in registry reviews, but there has been no significant difference in outcomes between patients treated with and without ECMO in meta-analyses. Considerable heterogeneity in studies is a significant weakness of the available literature. Applying ECMO is also associated with substantial multisystem morbidity due to a systemic inflammatory response, hemorrhagic stroke, renal dysfunction, and bleeding, which must be factored into the outcomes. The application of ECMO in MPE should be combined with an aggressive pulmonary interventional program and should strictly adhere to the current selection criteria.

Comparison of outcomes and complications in conventional versus ultrasound-accelerated catheter directed thrombolysis for treatment of pulmonary embolism: A systematic review and meta-analysis

BACKGROUND

Acute submassive a massive pulmonary embolism are known as leading causes of cardiovascular morbidity and mortality in emergency departments. Choosing the optimal type of catheter directed thrombolysis (CDT) for treatment of pulmonary embolism presents a quandary to the practitioners. To the best of our knowledge, there is no meta-analysis comparing superiority of conventional CDT and ultrasound-accelerated catheter directed thrombolysis (USACDT). Therefore, in this meta-analysis, we aimed to compare conventional CDT with USACDT regarding clinical outcomes and safety profile.

METHODS

A systematic literature search of previous published studies comparing conventional CDT with USACDT regarding clinical outcomes and safety profile was carried out in the electronic databases including MEDLINE, Scopus, EBSCO, Google Scholar, Web of Science, and Cochrane from inception to December 2021. Data were analyzed by comprehensive meta-analysis software (CMA, version 3).

RESULTS

The meta-analysis included nine studies with a total of 705 patients. Our meta-analysis showed that there is no significant difference between two groups with respect to pulmonary arterial systolic pressure (SMD: -0.084; 95% CI: -0.287 to 0.12; p: 0.41), RV/LV (SMD: -0.003; 95% CI: -0.277 to 0.270; p: 0.98), and Miller score (SMD: -0.345; 95% CI: -1.376 to 0.686; p: 0.51). Similarly, we found no statistically significant differences between two groups regarding major and minor bleeding (p > .05).

CONCLUSION

Our meta-analysis showed that when compared with USACDT, conventional CDT provides similar clinical and hemodynamic outcomes or safety for treatment of pulmonary embolism without the need for very expensive technologies. However, randomized clinical trials are required to further investigate cost-effectiveness of USACDT in comparison with conventional CDT.

Role of extracorporeal membrane oxygenation and surgical embolectomy in acute pulmonary embolism

PURPOSE OF REVIEW

Surgery is an important option to consider in patients with massive and submassive pulmonary emboli. Earlier intervention, better patient selection, improved surgical techniques and the use of veno-arterial extracorporeal membrane oxygenation (VA ECMO) have contributed to improve the safety of surgery for pulmonary emboli.

RECENT FINDINGS

VA ECMO is rapidly changing the initial management of patients with massive pulmonary emboli, providing an opportunity for stabilization and optimization before intervention. The early and long-term consequences of acute pulmonary emboli are better understood, in particular with regard to the risks of chronic thromboembolic pulmonary hypertension (CTEPH), an entity that should be identified in the acute setting as much as possible. The presence of chronic thromboembolic pulmonary disease can be associated with persistent haemodynamic instability despite removal of the acute thrombi, particularly if pulmonary hypertension is established. The pulmonary embolism response team (PERT) is an important component in the management of massive and submassive acute pulmonary emboli to determine the best treatment options for each patient depending on their clinical presentation.

SUMMARY

Three types of surgery can be performed for pulmonary emboli depending on the extent and degree of organization of the thrombi (pulmonary embolectomy, pulmonary thrombo-embolectomy and pulmonary thrombo-endarterectomy). Other treatment options in the context of acute pulmonary emboli include thrombolysis and catheter-directed embolectomy. Future research should determine how best to integrate VA ECMO as a bridging strategy to recovery or intervention in the treatment algorithm of patients with acute massive pulmonary emboli.

Management of High-Risk Pulmonary Embolism: What Is the Place of Extracorporeal Membrane Oxygenation?

Pulmonary embolism (PE) is a common disease with an annual incidence rate ranging from 39-115 per 100,000 inhabitants. It is one of the leading causes of cardiovascular mortality in the USA and Europe. While the clinical presentation and severity may vary, it is a life-threatening condition in its most severe form, defined as high-risk or massive PE. Therapeutic options in high-risk PE are limited. Current guidelines recommend the use of systemic thrombolytic therapy as first-line therapy (Level Ib). However, this treatment has important drawbacks including bleeding complications, limited efficacy in patients with recurrent PE or cardiac arrest, and formal contraindications. In this context, the use of venoarterial extracorporeal membrane oxygenation (VA-ECMO) in the management of high-risk PE has increased worldwide in the last decade. Strategies, including VA-ECMO as a stand-alone therapy or as a bridge to alternative reperfusion therapies, are associated with acceptable outcomes, especially if implemented before cardiac arrest. Nonetheless, the level of evidence supporting ECMO and alternative reperfusion therapies is low. The optimal management of high-risk PE patients will remain controversial until the realization of a prospective randomized trial comparing those cited strategies to systemic thrombolysis.