ECMO & Afterload

Date
August 8, 2025
URL
https://x.com/WithAScalpel/status/1953781274109161619
Categories
ECMOIntensive Care

ECMO and Afterload — Strategies for Left Ventricular Unloading in VA-ECMO

Pathophysiology

In veno-arterial ECMO (VA-ECMO), retrograde aortic flow increases LV afterload. If excessive, the aortic valve (AV) may not open, native ejection ceases, and pulmonary venous return continues to fill the LV → progressive distension, rising LVEDP, pulmonary congestion/edema, and intracavitary stasis with thrombus risk [1]. This is the central paradox of VA-ECMO: systemic support can simultaneously impede LV recovery unless unloading is applied.

Recognizing When to Unload

Bedside cues include absent AV opening on echo, vanishing pulse pressure, rising LV/LA dimensions or filling pressures, and worsening pulmonary edema; laboratory surrogates (e.g., lactate) and arterial line pulsatility inform the trend. Importantly, institutional triggers vary and there is no universally accepted threshold—highlighting the need for protocolized, team-based assessment [2].

Concept of LV Decompression

The aim is to relieve distension, restore intermittent AV opening and forward flow, and prevent secondary injury. Approaches span ECMO-setting adjustments, pharmacologic support, and mechanical unloading, often combined and escalated based on hemodynamics and imaging [3–5]. Evidence synthesis suggests any unloading strategy outperforms no unloading for mortality, with preload-reduction approaches potentially superior to isolated afterload reduction (methodological caveats apply) [6].

Interventional or Mechanical Options

  • Atrial septostomy (ASD creation): creates an LA→RA shunt to offload LA/LV and reduce pulmonary congestion [3,4].
  • Left-atrial venting: surgical or percutaneous (e.g., transseptal) cannulation for continuous drainage [3,4].
  • Impella / percutaneous microaxial pump: active LV unloading into the aorta; may be combined with VA-ECMO (“ECMELLA”) to mitigate distension when native contractility is poor [5,7].

Adjustments in ECMO Management

  • Reduce ECMO flow (as tolerated) to lower retrograde aortic pressure and encourage AV opening.
  • Judicious inotropes to promote native ejection, balanced against higher O₂ demand and ischemia risk [1,5].

Timing and Outcomes

Early recognition and timely unloading are emphasized across reviews, but optimal timing and modality remain debated; selection should reflect patient phenotype (ischemic vs myocarditis, pulmonary status), device availability, and local expertise [2,5]. Contemporary reviews reiterate the need for individualized algorithms and vigilant surveillance for complications (stroke/embolism, limb ischemia, hemolysis) [8].

Practical Bedside Algorithm (summary)

  1. Suspect LV distension (echo AV non-opening, low pulsatility, rising LVIDd/LA pressures, pulmonary edema).
  2. Optimize settings: carefully lower ECMO flow, adjust ventilator to reduce pulmonary venous return where appropriate, add low-dose inotrope to promote ejection.
  3. Definitive unloading: ASD/LA vent for rapid decompression; Impella if severe systolic failure or persistent AV non-opening.
  4. Reassess continuously (echo, perfusion, lactate) and de-escalate devices as recovery permits [1–5,7,8].

Clinical Relevance

Unchecked LV distension on VA-ECMO propagates a cycle of pulmonary edema, impaired oxygen delivery, coronary underperfusion, and thromboembolism. Protocolized monitoring for AV opening and timely deployment of unloading strategies are therefore central to safe ECMO practice and may improve survival versus no unloading [1,6,8].

References

[1] O. Saeed, Jose I. Nunez, U. Jorde. Pulmonary Protection from Left Ventricular Distension in Venoarterial Extracorporeal Membrane Oxygenation: Recognition and Management Algorithm. Lung. 2023. doi:10.1007/s00408-023-00616-8.

[2] Anthony Calhoun, Min-Ho Lee, Dominic V. Pisano, Alexandros Karamasis, et al. Variability in triggers for mechanical left ventricular venting during VA-ECMO: A survey study. Journal of Extra-Corporeal Technology. 2024. doi:10.1051/ject/2024031.

[3] M. Cevasco, H. Takayama, M. Ando, A. Garan, Y. Naka, K. Takeda. Left ventricular distension and venting strategies for patients on venoarterial extracorporeal membrane oxygenation. Journal of Thoracic Disease. 2019. doi:10.21037/JTD.2019.03.29.

[4] Ashleigh Xie, P. Forrest, A. Loforte. Left ventricular decompression in veno-arterial extracorporeal membrane oxygenation. Annals of Cardiothoracic Surgery. 2019. doi:10.21037/acs.2018.11.07.

[5] S. Ezad, M. Ryan, D. Donker, F. Pappalardo, N. Barrett, L. Cholley, et al. Unloading the Left Ventricle in Venoarterial ECMO: Who, When, and How? Circulation. 2023. doi:10.1161/CIRCULATIONAHA.122.062371.

[6] L. Baldetti, M. Gramegna, A. Beneduce, F. Melillo, F. Moroni, et al. Strategies of left ventricular unloading during VA-ECMO: a network meta-analysis. International Journal of Cardiology. 2020. doi:10.1016/j.ijcard.2020.02.004.

[7] J. P. Ricarte Bratti, Y. Cavayas, P. Noly, K. Serri, Y. Lamarche. Modalities of Left Ventricle Decompression during VA-ECMO Therapy. Membranes. 2021. doi:10.3390/membranes11030209.

[8] Yongwhan Lim, Min Chul Kim, In-Seok Jeong. Left ventricle unloading during veno-arterial extracorporeal membrane oxygenation: current evidence and future directions. Acute and Critical Care. 2024. doi:10.4266/acc.2024.00801.