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

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.