Hidden danger of microaxial flow pumps: Five cases of aortic and innominate mural thrombi

Surgically implanted microaxial flow pumps (Impella 5.5, Abiomed, Danvers, MA) are increasingly used as a bridge to heart transplantation (BTT) or bridge to durable left ventricular assist device (LVAD) implantation, yet thrombotic complications remain incompletely characterized. We report 5 cases of aortic or innominate mural thrombi during Impella 5.5 support. Among 90 patients supported with Impella 5.5 as a BTT or bridge to LVAD between 2021 and 2025, 5 (5.5%) developed mural thrombi. Four patients underwent successful transplantation or LVAD implantation following thrombectomy or conservative management, while 1 patient experienced a fatal embolic stroke. These findings highlight an under-recognized mechanism of embolic stroke in patients supported with Impella 5.5 as a BTT or bridge to LVAD, and raise important considerations regarding anticoagulation targets, device explant techniques, and management of embolic complications. Further investigation is warranted to establish prevention and treatment strategies for this growing challenge.