Cardiac MRI prediction of recovery in children with acute myocarditis

Myocarditis, defined as inflammation of myocardial tissue, is a rare disease in the pediatric population. Cardiovascular cardiac magnetic resonance (CMR) is a powerful tool for noninvasive assessment of myocardial inflammation as defined by the Lake Louise criteria, with a sensitivity of approximately 82% [1] . CMR allows tissue characterization of the myocardium, as well as accurate definition of ventricular volumes and function. Few prognostic factors have been associated with either normalization of function or progression to dilated cardiomyopathy in pediatric myocarditis. In the present study, we aimed to describe CMR findings in a large cohort of pediatric patients with acute myocarditis and to assess disease evolution. Our study received the proper ethical oversight [CNIL (Commission nationale de l’informatique et des libertes) declaration 2130271 v 0]. Sixty-eight children younger than 18 years of age with clinical myocarditis and positive acute-phase myocardial inflammation, as defined by the Lake Louise criteria [2] , underwent follow-up CMR during a 12-year period (from March 2007 to March 2019). The first follow-up CMR study was performed at a median of 5 months after the first examination (interquartile range: 1 to 6 months), and additional CMR studies were performed in 47% of the cohort (32 patients). Patient characteristics are presented in Table 1 . Most of the cohort were males (73.5%) who presented with chest pain (68%) or new-onset heart failure (33%). Fever was found in 55% of the cohort. Full recovery from acute myocarditis, as defined by normalization of ventricular function [left ventricular ejection fraction (LVEF) > 55%, right ventricular EF > 54%], ventricular dimensions (LV end-diastolic volume index [3] . This difference might translate to a higher healing ability of pediatric patients from tissue damage, as seen in other medical conditions. This complete healing of myocardial tissue abnormalities might be clinically relevant because residual fibrosis was associated with worse prognosis independently of LVEF [3] , [4] . In our study, an LGE pattern other than sub-epicardial was associated with non-recovery. This result was concordant with a recent study by Aquaro et al. [5] , who demonstrated a worse prognosis in association with a mid-wall septal pattern of LGE compared with a sub-epicardial inferior-lateral pattern. In conclusion, we found that fever at presentation was associated with full recovery from acute myocarditis, whereas specific acute-phase CMR findings (positive T2 criteria, LGE presence, and patterns other than sub-epicardial) were associated with its absence.