Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): The CARDIOCOV project - Prototype for personalized assessment of cardiovascular risk and post-Covid myocarditis based on artificial intelligence, advanced medical imaging and cloud computing - financed by UEFISCDI PN-III-P2-2.1-PTE-2021-0450 (Contract Number 108PTE/2022). Background Myocarditis following SARS-COV-2 infection has recently become a subject of concern, being detected in a significant number of post-COVID-19 patients who undergo cardiac magnetic resonance(CMR) examination. While the role of CMR in detecting presence of viral myocarditis has been well established, the CMR features associated with significant alteration of ventricular function in post-COVID patients are not clearly identified yet. Purpose The aim of the study was to investigate the role of myocardial edema (ME) at CMR for predicting the evolution of ventricular function in patients with COVID myocarditis. Methods In total, 55 patients with CMR signs of viral myocarditis following COVID-19 infection (52.72% males, mean age 36.85+/-16.29) were enrolled in the study. The delayed gadolinium enhancement phase-sensitive inversion recovery sequences were used for characterization of the myocardial tissue, and inversion recovery images showing high signal intensity were considered suggestive of edematous changes. Patients were divided into 2 study groups, according to the presence of myocardial edema at the moment of CMR evaluation: group 1 (n=18, 32.72%) - patients without ME, and group 2 (n=37, 67.27%)-patients with ME identified by CMR. In all patients, end-distolic and end-systolic volume indexes (EDVI and ESVI), ejection fraction (EF) and stroke volume (SV) were calculated. Results Compared to patients without ME, those with ME present at CMR were older n (42.9+/-14.8 vs. 36.7+/-16.6, p = 0.145) and more frequently males(59.4% vs. 38.8%). At the same time, EF was significantly lower in patients with ME(50.9+/-14.5% in group 2 vs. 58.4+/-10.2% in group 1, p = 0.03). Patients from group 2 also exhibited a more pronounced dilatation of ventricular cavities, as reflected by a significant increase of ventricular volumes and especially of the ESVI(109.8+/-125.9 versus 80.1+/-14.2, p = 0.5 for EDVI, and 65.2+/-109.1 vs. 30.0+/-11.4, p = 0.02 for ESVI). Compared to the group without ME, those with ME presented a significantly lower stroke volume index: 44.2+/-17.3 in group 1 vs. 47.7+/-7.5, p = 0.03 in group 2. Conclusions In patients with COVID-19 myocarditis, presence of ME at CMR imaging is associated with a worse evolution of the left ventricular function, as reflected by increased ventricular dilatation and decreased cardiac output in the post-COVID period.