The goal of this observational study is to determine the efficacy a of combined management and treatment driven by the systematic determination of viral genome, bacterial serology, and markers of inflammation in pediatric patients (\< 18 years old) diagnosed with myocarditis complicated by arrhythmias (supraventricular and ventricular tachycardias and heart block) or ventricular dysfunction (left ventricular ejection fraction \< 50% or right ventricular fractional area change \< 35%). The main question it aims to answer is: Does this panel help resolve arrhythmias or myocardial dysfunction due to myocarditis during hospitalisation and follow-up? Researchers will compare patients managed and treated in 2024 without applying the myocarditis panel with those enrolled in 2025 who received the panel. Arrhythmias and myocardial dysfunction will be managed in accordance with recent guidelines. Antiviral, antibiotic or immunosuppressive therapies will be implemented in addition to standard therapy when required by the panel.