Free floating thrombus in the ascending aorta after extracorporeal cardiopulmonary resuscitation: a case series.

Background: Extracorporeal cardiopulmonary resuscitation (ECPR) using venoarterial extracorporeal membrane oxygenation (V-A ECMO) is an advanced resuscitative measure to improve survival in refractory cardiac arrest. Although ECPR allows for organ perfusion during critical interventions, it carries a high-risk of complications, including thrombosis. Thrombus formation within the ECMO circuit and the patient's vasculature is common, yet focal ascending aortic thrombosis following ECPR is rarely reported. Case summary: We present two case reports of out-of-hospital cardiac arrest managed with ECPR that developed unexpected floating thrombi in the ascending aorta. The first patient, a 45-year-old woman with suspected myocarditis, developed a thrombus that obstructed the left main coronary artery, necessitating surgical thrombus extraction. Despite successful intervention, her cardiac function remained poor, and she required a heart transplant. The second patient, a 46-year-old woman with acute coronary syndrome, had a floating thrombus discovered incidentally. She was managed conservatively but later suffered brain death secondary to cerebral embolism. Discussion: Ascending aortic thrombosis is an underrecognized complication of ECPR, particularly in patients with non-ejecting hearts. Surgical removal of aortic thrombi, as performed in the first case, may prevent embolic events but lacks standardized guidelines. These cases underscore the need for heightened awareness, early detection, and development of management protocols to mitigate thrombotic risks in ECPR patients. Further studies are warranted to establish treatment strategies for this rare but severe complication.