Physiology of Unloading VA ECMO Trial

Although extracorporeal membrane oxygenation (ECMO) for cardiogenic shock (CS) is used in over 3,000 patients per year, the best management strategies are not known. Identifying and improving treatment of CS is critically important, as CS occurs in 160,000 patients per year in the US with a 50% mortality rate. VA ECMO is an increasingly used method of mechanical circulatory support (MCS) for patients with CS refractory to medical therapy. Despite the benefit of full cardiopulmonary support ECMO is also thought to increase after load in the failing heart- which paradoxically reduces cardiac output and may lead to myocardial injury and cardiac congestion. A potential solution is to add a device to VA ECMO that decreases after-load - known as left ventricular (LV) unloading. LV unloading can be achieved with different approaches, directly with transvalvular pumps (known as a peripheral ventricular assist device (pVAD)), or indirectly with an intra-aortic balloon pump (IABP) Preliminary data suggests that unloading the LV is associated with improved survival. Results from a cohort of VA ECMO patients with medical CS, showed a hospital survival benefit LV unloading (aOR 0.87 (0.79, 094); p=0.001). Data has also shown that the survival benefit of LV unloading was much larger with pVAD (HR 0.6), but with higher complications, including limb ischemia - a potentially catastrophic complication. However, results also show that different unloading approaches have different physiologic effects on the myocardium and on peripheral perfusion - highlighting the uncomfortable observation that it is not known how (physiologically) these unloading devices lead to changes in survival. There are two potential pathways whereby LV unloading could influence survival, including myocardial effects (distension, injury, ejection fraction ) and peripheral effects (peripheral pulse pressure, lactate clearance, CO2 gap). Determining the physiologic effects from LV unloading according to device type and patient etiology will allow us to match the intervention with the patient's physiology. Data suggests that ECMO patients with acute myocardial infarction (AMI) have different mortality and different physiologic changes than patients with decompensated chronic heart failure (CHF) when unloaded. The ultimate goal is to reduce morbidity and mortality in cardiogenic shock. This study will define the physiologic benefit of LV unloading during CS.