There is no doubt that veno-arterial extracorporeal membrane oxygenation (VA ECMO) in cardiogenic shock (CS) has saved thousands of lives over the last decade. A feared complication, occasionally difficult to manage, is LV distention due to lack of unloading. Protocolized measures for loss of pulsatile wave in arterial pressure monitoring—a patient emergency under ECMO support—are well known and effective (arrhythmia correction, flow reduction, blood pressure lowering, inotropy increase). However, when these are insufficient, indirect LV unloading methods, like IABP, or more direct ones, such as the Impella® device (Abiomed®, Danvers, Massachusetts, USA), are available. This study sought to evaluate the clinical and hemodynamic effects of IABP and Impella® devices in patients on VA ECMO support.

A retrospective review was conducted on VA ECMO patients at Columbia Hospital (New York) from January 2015 to June 2020. Patients were classified as receiving isolated ECMO or ECMO with LV unloading via IABP or Impella®. Clinical pre-ECMO characteristics, survival, complications, and hemodynamic changes associated with each device initiation were recorded. A total of 143 patients received isolated ECMO, while 140 received ECMO with LV unloading (68 ECMO with IABP, 72 ECMO with Impella®). Patients on ECMO with Impella® had a higher incidence of bleeding events compared with isolated ECMO or ECMO with IABP (52.8% vs. 37.1% vs. 17.7%; p < 0.0001). Compared with isolated ECMO, ECMO with IABP showed better survival at 180 days (p = 0.005), while there were no significant survival differences when compared to ECMO with Impella®. In a multivariable Cox hazard analysis, age (HR = 1.02; p= 0.015), pre-ECMO lactate levels (HR = 1.06; p = 0.004), pre-ECMO creatinine (HR = 1.06; p = 0.032), and need for ECMO in cardiopulmonary resuscitation settings (HR = 2.09; p = 0.001) were independent risk factors for mortality, whereas male sex (HR = 0.54; p = 0.002) and pre-ECMO IABP presence (HR = 0.45; p = 0.010) acted as independent protective factors. There were no significant hemodynamic differences between ECMO with IABP and ECMO with Impella® cohorts.

The authors concluded that concomitant IABP support may help reduce morbidity and improve 180-day survival in VA ECMO patients with cardiogenic shock.

COMMENTARY:

Despite advancements in CS pathophysiology and management, mortality remains excessively high. Devices such as IABP, ECMO, or Impella® have revolutionized shock treatment, particularly at severe stages (D and E). While peripheral VA ECMO can be life-saving in CS as a bridge to recovery or other long-term therapies, LV unloading is essential to prevent LV distention (LVD) and its potential sequelae like acute pulmonary edema, thrombosis/embolism, and lack of ventricular recovery. Depending on clinical circumstances, LVD patients may require afterload reduction, increased contractility, or additional mechanical support, such as IABP or left ventricular assist devices (LVAD) (e.g., Impella®). Determining the best approach in such scenarios remains a scarcely debated challenge. The diversity in CS etiology, severity, and duration before initiating therapy makes comparing unloading strategies difficult, especially in a study like Char et al.’s, with a limited sample size. Moreover, the inclusion of ECMO patients due to cardiopulmonary resuscitation (extracorporeal cardiopulmonary resuscitation, ECPR) further complicates evaluation, as these patients are at a particularly high risk of death, anoxic brain injury, multi-organ failure, and LVD. The 2021 AHA ECPR expert consensus guidelines recommend IABP, direct LV drainage cannula, Impella®, or atrial septostomy for LV unloading; however, they do not detail specific diagnostic criteria for LVD or optimal timing for intervention.

Given the urgency and clinical variability in CS presentations, it is understandable why prospective randomized trials are nearly impossible. Consequently, studies like this, though retrospective with limited sample sizes, provide essential evidence in a field with many uncertainties, especially when they include hemodynamic data on the impact of different support devices.

Following the analysis of 300 VA ECMO patients, the main finding of Char et al.’s study was that LV unloading did not improve discharge survival or 180-day outcomes, despite improved hemodynamic status in ECMO patients. When the two unloading methods were analyzed separately, patients with IABP showed better survival, particularly when IABP was implanted preventively before LVD onset. On the other hand, Impella® patients had a higher incidence of bleeding complications. Survival differences must be interpreted cautiously due to inherent selection bias, as device choice was not randomized, a limitation that multivariable analysis cannot mitigate in a retrospective study.

These results suggest that, as both procedures are equally effective for hemodynamic stabilization in ECMO patients with LVD, IABP may be preferable for initial LV unloading due to its bedside implantability and removal, even without fluoroscopy, and lower bleeding risk compared to Impella®. The authors advocate for systematic early IABP use in patients who may eventually require ECMO. In our daily practice, patients without ventricular function recovery after a few days often end up on urgent transplant waiting lists, requiring not only IABP but also additional LV unloading systems, frequently Impella® in our hospital, or other techniques, depending on variables such as LV dysfunction severity, thrombus presence in the ventricular wall, aortic insufficiency, concomitant pathologies, and transplant center experience. LV unloading method selection is complex, and while this study does not provide definitive information, it is a step forward in this area. This work adds valuable nuances to the discussion of LV unloading approaches in VA ECMO patients.

Finally, it is crucial to recognize that within a short period, many patients who would have succumbed to cardiopulmonary collapse a decade ago can now be rescued by VA ECMO (pre-hospital ECMO, regional/provincial “Shock Code” programs) and even transitioned to longer-term therapies. We must acknowledge the profound impact this therapy can have on patients previously facing certain death. Every decision and detail that can improve the management of this condition is vital and contributes exponentially to knowledge expansion in this promising field of medicine.

REFERENCE

Char S, Fried J, Melehy A, Mehta S, Ning Y, Kurlansky P, Takeda K. Clinical efficacy of direct or indirect left ventricular unloading during venoarterial extracorporeal membrane oxygenation for primary cardiogenic shock. J Thorac Cardiovasc Surg. 2023 Feb;165(2):699-707.e5. doi: 10.1016/j.jtcvs.2021.06.024

Baran DA, Grines CL, Bailey S, Burkhoff D, Hall SA, Henry TD, et al. SCAI clinical expert consensus statement on the classification of cardiogenic shock: This document was endorsed by the American College of Cardiology (ACC), the American Heart Association (AHA), the Society of Critical Care Medicine (SCCM), and the Society of Thoracic Surgeons (STS) in April 2019. Catheter Cardiovasc Interv. 2019 Jul 1;94(1):29-37. doi: 10.1002/ccd.28329

Richardson ASC, Tonna JE, Nanjayya V, Nixon P, Abrams DC, Raman L, et al. Extracorporeal Cardiopulmonary Resuscitation in Adults. Interim Guideline Consensus Statement from the Extracorporeal Life Support Organization. ASAIO J. 2021 Mar 1;67(3):221-228. doi: 10.1097/MAT.0000000000001344