ECPELLA Mixing Cloud on Computed Tomography Angiogram

ECPELLA is the simultaneous use of an Impella (Abiomed, USA), a percutaneous transvalvular microaxial flow pump, and venoarterial extracorporeal membrane oxygenation for mechanical circulatory support.1,2A 53-yr-old male with ischemic cardiomyopathy was bridged to heart transplantation using ECPELLA support. His venoarterial extracorporeal membrane oxygenation circuit consisted of a right femoral vein drainage cannula and a left femoral artery return cannula. He had an Impella 5.5 in place through his right axillary artery. A computed tomography angiogram showed the mixing cloud present when the antegrade flow from the heart and the Impella 5.5 meets the retrograde flow from the peripheral venoarterial extracorporeal membrane oxygenation return cannula. The distal aorta lacked contrast in both early and late arterial phase images, making this finding unlikely to be an artifact of inappropriately early imaging after contrast injection.Differential hypoxemia (Harlequin or North-south syndrome) is a phenomenon seen in patients on ECPELLA support with concurrent lung pathology. Poorly oxygenated blood from the lungs is pumped by the heart and the Impella to the upper body while the lower body is perfused by well-oxygenated blood from the peripheral venoarterial extracorporeal membrane oxygenation circuit. Differential hypoxemia places a patient at risk of cerebral or myocardial hypoxia. To improve differential hypoxemia, the cardiac output from the heart needs to be decreased. This can be achieved by decreasing the Impella flow, decreasing inotropic support or both. These changes result in relatively increased retrograde flow of well-oxygenated blood from the peripheral venoarterial extracorporeal membrane oxygenation return cannula and thus a shift of the mixing cloud more proximally. Arterial blood gases from three different arterial sites (right radial artery, left radial artery, and extracorporeal membrane oxygenation arterial line) can help localize the mixing cloud and aid in management.3 In refractory cases, extracorporeal membrane oxygenation circuit reconfiguration may be necessary.This image of a mixing cloud demonstrates the interdependence of the two mechanical circulatory devices in ECPELLA support. As ECPELLA support is utilized more frequently, an understanding of the unique physiology is imperative for physicians caring for these patients in the operating room and intensive care unit.The authors declare no competing interests.