Objective: To describe clinical outcomes and evaluate the safety of patients undergoing cardiac catheterization during extracorporeal membrane oxygenation (ECMO) support. Methods and results: A retrospective review of cardiac catheterizations performed in patients under 18 years old while receiving ECMO support at a high-complexity cardiovascular reference center. Data were collected from the ECMO database, medical notes, catheterization reports, surgeries, echocardiograms, and radiology. This study was approved by the institution's ethics committee. A total of 117 patients were on ECMO between January 2012 and December 2023, of which 33% (39) underwent at least one catheterization while receiving support. A total of 44 catheterizations were performed in the 39 patients. Indications for ECMO included failure to wean from cardiopulmonary bypass (18 patients), ventricular dysfunction (14 patients), and persistent cyanosis and/or hypoxemia (10 patients). In 52.3% of catheterizations, some intervention was performed; the main indications were pulmonary artery angioplasty and/or stent implantation (9), atrial septostomy (5), one of which was performed during ex-utero intrapartum treatment (EXIT), Glenn stent implantation (2), Fontan fenestration angioplasty (1), aortopulmonary collateral artery embolization (2), right ventricular outflow tract stent implantation (2), while indications for diagnostic catheterization included endomyocardial biopsy (2), hemodynamic evaluation, pulmonary artery, pulmonary vein, aorta, coronary angiographies, and evaluation of surgical repair (21). The median ECMO duration was 6.8 days (IQR 3.98–14.56), and the median time from cannulation to catheterization was 1 day (IQR 0.37–3.69). Catheterization was performed on day 0-1 of the ECMO cycle in 26 patients (66.7%) and after day 1 in 12 patients (33.3%). In patients who underwent catheterization more than 24 hours after cannulation (late catheterization), survival was 22.7%, while in those who underwent catheterization within the first 24 hours from cannulation (early catheterization), survival was 66.2%.The 40.9% had an univentricular physiology, while 52% were biventricular, and 6.8% had some form of cardiomyopathy.There was one major complication during catheterization (2.27%), consisting of intra-atrial and left ventricular thrombi in a patient with dilated cardiomyopathy. Overall results included successful decannulation in 60% of patients, with most deaths on ECMO having univentricular cardiovascular anatomy (10). ECMO support was withdrawn in 6 cases (37.5% of deaths) due to severe neurological injury and 1 case due to secondary pulmonary hemorrhage from reperfusion. Survival to hospital discharge was 30%. Conclusion: Cardiac catheterization can be safely performed in patients supported by ECMO. Catheterization during ECMO allows for the diagnosis of residual lesions and may facilitate significant therapeutic interventions that could improve patient prognosis |