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Mechanical LV Unloading in Patients Undergoing VA-ECMO
Quick Takes
- For adult patients on peripheral VA-ECMO support, LV mechanical unloading is associated with lower in-hospital mortality but increased rates of device-related complications.
- For patients receiving mechanical unloading on VA-ECMO, IABP use has similar survival but lower complication rates compared to percutaneous VAD devices.
Study Questions:
What are the outcomes associated with left ventricular (LV) mechanical unloading (MU) in patients supported with venoarterial extracorporeal membrane oxygenation (VA-ECMO)?
Methods:
The authors used data from the multicenter, international Extracorporeal Life Support Organization (ELSO) registry for this retrospective analysis. They included adult patients receiving VA-ECMO via peripheral cannulation from 2010–2019. Patients were excluded if they had multiple runs of VA-ECMO, central cannulation, nonfemoral vessel peripheral cannulation, pulmonary embolism as the primary indication, heart transplant, congenital heart disease, or certain valve pathologies that precluded MU use.
MU use was defined as upfront (either present prior or placed at the time of VA-ECMO initiation) or delayed (placed after VA-ECMO initiation). Devices used for MU were specified, including intra-aortic balloon pumps (IABPs) and percutaneous left ventricular assist devices (pVADs). In comparisons of IABP and pVAD outcomes, only registry data from 2017–2019 was used, as this was the time when pVAD data was available.
The primary outcome was in-hospital mortality. The secondary outcomes were on-support mortality and complications from VA-ECMO (bleeding, hemolysis, ischemic stroke, limb ischemia, renal injury).
Results:
There were 12,734 VA-ECMO patients included in this analysis. Of these, 3,399 (26.7%) received LV mechanical unloading and 9,335 (73.3%) did not. Of the patients receiving MU, IABP was used in 2,782 (82.9%) and pVAD was used in 580 (17.1%) cases. MU use was stable over the years (about 25% of cases), though increased in the last 2 years studied to about 35% of cases in 2019. Of these MU cases in 2019, 46.4% were with pVAD. Most patients receiving MU had an upfront placement strategy (n = 2,937, 86.4%). Patients receiving MU were significantly more likely to be older, male, white, have acute myocardial infarction (AMI) as the primary indication, have end-organ (respiratory, renal, liver) failure, and need >2 vasopressors.
Primary outcome—Patients with MU compared to no MU had:
- Lower in-hospital mortality (56.6% vs. 59.3%; p = 0.006). This finding persisted after multivariable adjustment (adjusted odds ratio [aOR], 0.84; 95% confidence interval [CI], 0.77-0.92; p < 0.001).
- Subgroup analysis revealed a potential larger benefit in patients aged <50 years and those with cardiac arrest before VA-ECMO initiation.
Secondary outcomes—Patients with MU compared to no MU had:
- Lower unadjusted on-support mortality (41.5% vs. 47.9%; p < 0.001) and this finding persisted after multivariable adjustment (aOR, 0.77; 95% CI, 0.70-0.84; p < 0.0001).
- Higher unadjusted rates of medical bleeding, cannula site bleeding, tamponade, hemolysis, ischemic stroke, limb ischemia, renal injury.
- Higher adjusted rates of cannula site bleeding (aOR, 1.25; 95% CI, 1.11-1.40; p < 0.001), hemolysis (aOR, 1.27; 95% CI, 1.03-1.57; p = 0.02).
Other outcomes—MU with IABP (n = 1,123) compared to pVAD (n = 555) had:
- Lower rates of respiratory, renal, liver failure (p < 0.001 for all).
- Similar in-hospital mortality (aOR, 0.80; 95% CI, 0.64-1.01; p = 0.06).
- Lower rates of medical bleeding (aOR, 0.45; 95% CI, 0.31-0.64; p < 0.001), cannula site bleeding (aOR, 0.72; 95% CI, 0.54-0.96; p = 0.03), renal injury (aOR, 0.78; 95% CI, 0.62-0.98; p = 0.03).
Conclusions:
In adult patients requiring peripheral VA-ECMO support, the use of an LV MU strategy compared to no MU was associated with lower in-hospital and on-support mortality. Complication rates of cannula site bleeding and hemolysis were higher with MU. MU with IABP compared to pVAD had similar in-hospital mortality but lower complication rates.
Perspective:
VA-ECMO remains an important therapeutic option for patients who are post–cardiac arrest and have refractory cardiogenic shock. Peripheral cannulation for VA-ECMO leads to retrograde proximal aortic blood flow that causes increased LV afterload. Possible consequences of this include LV distension, reduction in stroke volume, pulmonary edema, intracardiac thrombus formation, worsened coronary perfusion pressure, and impairment in LV recovery. Mechanical unloading with devices like IABPs and pVADs are commonly utilized and have seen a significant increase in use over the last few years, primarily driven by pVAD use. However, there is a lack of data on the exact role of MU in these situations, which is why the authors of this study explored this issue further. Based on the results of this analysis, it would suggest that mechanical LV unloading is associated with mortality benefit but comes at the cost of increased complications related to mechanical support. Randomized controlled trials are still needed to definitively provide guidance in this area, however.
The authors also interestingly compare MU with IABP versus pVAD. These devices have similar rates of mortality but fewer complications were observed with IABP use. Again, while not definitive and subject to confounding, these results should make clinicians think carefully about selecting the MU device for a given situation that offers the best balance of risks and benefits.
Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Vascular Medicine, Implantable Devices, SCD/Ventricular Arrhythmias, Cardiac Surgery and Arrhythmias, Cardiac Surgery and Heart Failure, Acute Heart Failure, Heart Transplant, Mechanical Circulatory Support, Interventions and Vascular Medicine
Keywords: Brain Ischemia, Cannula, Cardiac Surgical Procedures, Catheterization, Extracorporeal Membrane Oxygenation, Heart Arrest, Heart Failure, Heart Transplantation, Heart-Assist Devices, Hemolysis, Hemorrhage, Hospital Mortality, Intra-Aortic Balloon Pumping, Ischemic Stroke, Renal Insufficiency, Respiratory Insufficiency, Risk Assessment, Shock, Cardiogenic, Stroke, Thrombosis
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