Clinical Phenotypes and Early Risk Stratification in Pediatric Acute Myocarditis: A Single-Center Experience in the Postpandemic Context

Objectives: Pediatric acute myocarditis presents with a heterogeneous clinical spectrum. The primary aim of this study was to identify early clinical and laboratory predictors of severe disease requiring intensive care unit (ICU) admission. A secondary aim was to describe the clinical characteristics of cases diagnosed in the postpandemic context. Methods: We conducted a retrospective cohort study of children admitted to a tertiary center with acute myocarditis between 2012 and 2024. Patients requiring ICU admission were compared with those managed in standard wards to identify risk factors for severity. Data were analyzed using descriptive statistics, nonparametric tests, and effect size calculations. Results: Thirty-eight cases were identified, with 76% of diagnoses occurring after 2020. The median age was 12.5 years. Two distinct clinical phenotypes emerged: patients with chest pain (59%) and those with cardiogenic shock (15%). Admission to the ICU was strongly associated with hemodynamic instability (P < 0.001), lower left ventricular ejection fraction (P < 0.001), and the absence of reported chest pain (P < 0.001). Among biomarkers, higher levels of NT-pro-BNP (P = 0.005) and elevated Procalcitonin (P = 0.02) were associated with severe disease. Parvovirus B19 was the most frequently detected pathogen in the recent period. Conclusions: In our cohort, pediatric myocarditis presented with increased frequency in the postpandemic years. Risk stratification remains crucial: "infarct-like" chest pain was associated with a milder course in older children. Conversely, severe cases, often occurring in younger patients unable to report pain, were identified by hemodynamic stress (shock, elevated NT-pro-BNP) and systemic inflammation (procalcitonin).