Impella Motor Current Amplitude Reflects the Degree of Left Ventricular Unloading under ECPELLA Support.

ABSTRACT

The combination of venoarterial extracorporeal membrane oxygenation (VA-ECMO) and Impella, referred to as ECPELLA, is a powerful transient mechanical circulatory support for patients with severe cardiogenic shock (CS). During ECPELLA support, VA-ECMO loads the left ventricle (LV) and Impella unloads the LV. Therefore, evaluating the degree of LV unloading during ECPELLA may be a prerequisite to protect the injured myocardium. Here we report a patient with CS due to an inferior ST-elevation myocardial infarction in which the degree of LV unloading on ECPELLA was confirmed by direct LV pressure (LVP) measurement. After the percutaneous coronary intervention for the right coronary artery on ECPELLA, the aortic pressure became nonpulsatile and the peak systolic LVP was reduced at approximately 10 mmHg with 20 mA of the Impella motor current (MC) amplitude, which we referred to as the total LV unloading condition. We maintained the condition in the early phase of ECPELLA by monitoring the Impella MC amplitude at 20 mA and less with nonpulsatile aortic pressure. The patient was successfully weaned off VA-ECMO on day 3, and Impella was explanted on day 8. Prior to the Impella explant, the Impella MC amplitude increased more than 100 mA and the estimated pressure gradient between the aortic pressure and LVP was well matched with the directly measured LVP. In this case, the patient was successfully treated by ECPELLA with the total LV unloading condition, and we showed that the degree of LV unloading on ECPELLA can be estimated from the aortic pressure and Impella MC amplitude at given Impella flows.