This Concise Critical Appraisal explores a recent study that examined the use of venoarterial extracorporeal membrane oxygenation and microaxial flow pumps in seven healthy sheep, including whether the combined use is better than individual strategies.
When circulatory failure is refractory to conservative interventions and results in prolonged inadequate cardiac output, temporary mechanical circulatory support (MCS) such as venoarterial extracorporeal membrane oxygenation (VA-ECMO) and microaxial flow pumps may be required. Despite advances in MCS, mortality among patients with cardiogenic shock remains substantial. Each modality produces complex and distinct hemodynamic effects, making an understanding of their influence on cardiac workload, myocardial oxygen consumption, and systemic perfusion essential to appropriate device selection. Burkhoff et al demonstrated that MCS devices alter ventricular preload, afterload, and myocardial work in device-specific ways, emphasizing the importance of understanding pump-patient interactions.
1 Similarly, Chung et al highlighted the complexity of optimizing MCS to achieve adequate systemic perfusion while minimizing adverse ventricular loading conditions.
2 More recently, the DanGer Shock Investigators trial demonstrated a mortality benefit from microaxial flow pumps in selected patients with infarct-related cardiogenic shock, although this benefit was accompanied by increased device-related complications.
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Yastrebov et al compared the results of VA-ECMO, microaxial flow pumps, and their combined use (ECPELLA) in seven healthy adult sheep.
4 Establishing these physiological responses in normal hearts of sheep provides an important baseline for understanding how these modalities may behave in human patients with severe cardiac dysfunction.
The authors evaluated seven adult ewes with healthy hearts, with each animal undergoing two cycles of VA-ECMO, microaxial flow pumps, and ECPELLA.
4 Hemodynamic variables including systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), central venous pressure, total systemic blood flow (TSBF), left ventricular (LV) workload, coronary blood flow, and myocardial oxygen consumption were assessed across varying pump flows. All three MCS strategies increased arterial elastance while reducing LV myocardial work, coronary arterial flow, and myocardial oxygen consumption. VA-ECMO and microaxial flow pumps produced broadly similar effects on myocardial workload and oxygen consumption. However, ECPELLA was the only method that increased both MAP and TSBF, suggesting that its principal physiological advantage may be the ability to provide systemic circulatory support while simultaneously unloading the LV.
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The authors concluded that the additional complexity and invasiveness of ECPELLA may be most appropriate for patients with severe LV failure who require ventricular decompression. Combining devices, however, also combines their potential complications. Importantly, the study evaluated normal hearts with adequate baseline cardiac output and perfusion. Mechanical support in this model largely replaced normal cardiac function rather than augmenting a failing heart. The physiological response may differ substantially in cardiogenic shock, where impaired contractility, altered preload, increased afterload, and inadequate organ perfusion are already present.
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The study's primary limitations are its very small sample size, use of healthy sheep, and open-chest VA-ECMO model, which limits direct comparison with the closed-chest peripheral VA-ECMO model commonly used clinically.
4 Most notably, healthy hearts with normal coronary and systemic perfusion cannot replicate the complex physiology of cardiogenic shock. The study also assessed physiological variables rather than mortality, morbidity, or direct end-organ outcomes. Nevertheless, its significance lies in providing detailed physiological evidence that can inform MCS selection and management. In modern hospitals, where increasingly complex combinations of MCS are available, understanding when additional support provides meaningful benefit is essential. Further research in cardiomyopathic and shock models is necessary to determine whether ECPELLA provides clinically meaningful advantages that justify its increased cost, complexity, and complication burden.
References
- Burkhoff D, Sayer G, Doshi D, Uriel N. Hemodynamics of Mechanical Circulatory Support. J Am Coll Cardiol. 2015;66(23):2663-2674.
- Chung BB, Sayer G, Uriel N. Mechanical circulatory support devices: methods to optimize hemodynamics during use. Expert Rev Med Devices. 2017;14(5):343-353.
- Møller JE, Engstrøm T, Jensen LO, et al; DanGer Shock Investigators. Microaxial flow pump or standard care in infarct-related cardiogenic shock. N Engl J Med. 2024;390(15):1382-1393.
- Yastrebov K, Paterson HS, Tian DH, et al. Head-to-head comparison of V-A ECMO, Impella and ECPELLA in normal ovine hearts. Sci Rep. 2025;15(1):21368.
