Acute Crit Care.  2024 Nov;39(4):473-487. 10.4266/acc.2024.00801.

Left ventricle unloading during veno-arterial extracorporeal membrane oxygenation: review with updated evidence

• Lim Y
• Kim MC
• Jeong IS

• KMID: 2563536
• DOI: http://doi.org/10.4266/acc.2024.00801

Abstract

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is widely used to treat medically refractory cardiogenic shock and cardiac arrest, and its usage has increased exponentially over time. Although VA-ECMO has many advantages over other mechanical circulatory supports, it has the unavoidable disadvantage of increasing retrograde arterial flow in the afterload, which causes left ventricular (LV) overload and can lead to undesirable consequences during VA-ECMO treatment. Weak or no antegrade flow without sufficient opening of the aortic valve increases the LV end-diastolic pressure, and that can cause refractory pulmonary edema, blood stagnation, thrombosis, and refractory ventricular arrhythmia. This hemodynamic change is also related to an increase in myocardial energy consumption and poor recovery, making LV unloading an essential management issue during VA-ECMO treatment. The principal factors in effective LV unloading are its timing, indications, and modalities. In this article, we review why LV unloading is required, when it is indicated, and how it can be achieved.

Keyword

cardiogenic shock; extracorporeal membrane oxygenation; heart-lung machine

Figure

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  Figure 1. Pressure volume curves describing normal left ventricular (LV) hemodynamics (A), pressure-volume area, sum of stroke work, and potential energy (B), cardiogenic shock with a decrease in contractility (arrow a) and stroke volume (b to b’) and an increase in LV end-diastolic volume and pressure (arrow c) (C), and veno-arterial ECMO during cardiogenic shock (D). LVP: left ventricular pressure; LVV: left ventricular volume; Ea: arterial elastance; ESPVR: end-systolic pressure-volume relationship; Ees: end-systolic elastance; EDPVR: end-diastolic pressure-volume relationship; LVEDV: LV end-diastolic volume; PVA: pressure-volume area; PE: potential energy; SW: stroke work; MVO2: myocardial oxygen consumption; ECMO: extracorporeal membrane oxygenation.

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  Figure 2. Pressure volume loop simulating left ventricular (LV) venting during veno-arterial extracorporeal membrane oxygenation. LVP: left ventricular pressure.

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  Figure 3. Suggestion of possible left ventricular (LV) unloading strategies. “Prophylactic” means unloading before any evidence of LV overload. “Therapeutic” means LV unloading to treat LV overload signs refractory to medical treatment. “Early” means performing mechanical LV unloading prior to medical treatment to ameliorate it. With the currently available evidence obtained from randomized controlled studies, we advocate for therapeutic rather than prophylactic or early LV unloading (the degree of recommendation). VA-ECMO: veno-arterial extracorporeal membrane oxygenation; SEC: spontaneous echo contrast; PCWP: pulmonary capillary wedge pressure: PEEP: positive end-expiratory pressure; CS: cardiogenic shock.

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  Figure 4. Pressure-volume loops for varying modalities of left ventricular (LV) unloading. Each modality has a specific mode of action that could have different effects on LV hemodynamics or energetics. CS: cardiogenic shock; ECMO: extracorporeal membrane oxygenation; PAS: percutaneous atrial septostomy; PAD: pulmonary artery drainage. Adapted from data obtained from animal models [14-17].

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