Let’s Vent about Venting the Left Ventricle: A VA-ECMO Study

Left ventricular mechanical unloading with intra-aortic balloon pump (IABP) or percutaneous ventricular assist device (pVAD) in patients on VA-ECMO was associated with lower in-hospital mortality but increased bleeding events, according to a study published in the Journal of the American College of Cardiology.¹

This study leveraged data from the Extracorporeal Life Support Organization registry between 2010 and 2019 from 463 centers across North America and Europe. The study included 12,734 adults managed with VA-ECMO, of which 3,399 received mechanical unloading (MU) (82.9% IABP versus 17.1% pVAD). Exclusion criteria were history of heart transplant, congenital heart disease, valvular or aortic disease, multiple VA-ECMO runs, central ECMO cannulation, or pulmonary embolism as the indication for VA-ECMO. Notably, patients who received MU were older, more often White, predominantly male, and more likely to have acute myocardial infarction (AMI). MU was associated with lower on-support (41.5% vs 47.9%; p<0.001) and in-hospital (56.6% vs 59.3%; p=0.006) mortality with a significant interaction effect in patients <50 years. There were no differences in mortality with an up-front MU strategy versus delayed (at the time of VA-ECMO cannulation) or with IABP versus pVAD use. MU was associated with more cannula site bleeding and hemolysis. However, the association between MU and hemolysis was not significant in a propensity-matched cohort. IABP versus pVAD use was associated with lower cannula site bleeding (13.2% vs 18.7%), medical bleeding (6.8% vs 14.1%), hemorrhagic stroke (1.9% vs 4.1%), and renal injury (31% vs 40.5%).

The optimal timing, selection, and duration of MU support continues to puzzle clinicians.² Prior studies suggest any unloading is better than none and preload unloading may be superior to afterload unloading.³ While this study corroborates previously described MU-associated survival benefit, it was unable to capture hemodynamic and echocardiographic variables to understand the underlying mechanisms. Furthermore, 86.4% of patients already had devices in place prior to ECMO cannulation, thereby limiting extrapolation that these were placed to manage left ventricular distension. There was no data on duration of shock prior to MU, or duration of MU after ECMO cannulation, thereby limiting understanding of optimal MU timing. Finally, most of the patients that received MU had AMI as their primary diagnosis, thus questioning generalizability of the results to heart-failure cardiogenic shock.

This study demonstrated improved mortality with MU albeit with increased bleeding events, suggesting the use of individualized care-plans. Future studies are still desperately needed to understand the optimal MU strategy for this critically ill patient cohort.

References:

1. Grandin EW, Nunez JI, Willar B, et al. Mechanical Left Ventricular Unloading in Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation. Journal of the American College of Cardiology. 2022;79(13):1239-1250. doi:10.1016/j.jacc.2022.01.032
2. Al-Fares AA, Randhawa VK, Englesakis M, et al. Optimal Strategy and Timing of Left Ventricular Venting During Veno-Arterial Extracorporeal Life Support for Adults in Cardiogenic Shock: A Systematic Review and Meta-Analysis. Circ Heart Fail. 2019;12(11):e006486. doi:10.1161/CIRCHEARTFAILURE.119.006486
3. Baldetti L, Gramegna M, Beneduce A, et al. Strategies of left ventricular unloading during VA-ECMO support: a network meta-analysis. International Journal of Cardiology. 2020;312:16-21. doi:10.1016/j.ijcard.2020.02.004