Histopathologic examination of myocardial tissue (autopsy or endomyocardial biopsy) showed myocardial inflammation YES No inflammation seen or not Level 1 Myocarditis done or results unknown (Definitive Case) 5 Elevated myocardial biomarkers (Troponin T and Troponin I) YES AND 5 Evidence of focal or diffuse depressed left ventricular function of indeterminate age in ≥1 imaging study: o Abnormal cardiac magnetic resonance (cMR)1 o Abnormalities in echocardiogram2 No 5 ≥ 1 Cardiac presentation 4 AND ≥ 1 Non-specific presentation 5 OR 5 ≥2 non-specific symptoms in infant/young child 6 YES No Alternative etiology for symptoms? NO Yes 5 Elevated myocardial biomarkers (Troponin T/I) OR (CK myocardial band) OR YES Level 2 Myocarditis 2 5 Echocardiogram abnormalities (Probable case) OR 5 Electrocardiogram abnormalities 3 No 5 ≥1 lab marker of inflammation (elevated CRP (C-Reactive Protein), ESR (Erythrocyte sedimentation rate) or D-Dimer YES Level 3 Myocarditis OR (Possible Case) 5 Nonspecific electrocardiogram abnormalities No Level 4 is a reported event of myocarditis with insufficient Level 5: NOT a case of Myocarditis evidence to meet level 1,2 or 3 of the case definition 1 cMR Abnormalities: 2 Echocardiogram abnormalities: 3 Electrocardiogram abnormalities: o Patchy edema on T2 weighted o New left or right ventricular function abnormalities o ST-segment or T-wave images including: segmental wall motion abnormalities; abnormalities (elevation or o Late gadolinium enhancement on T1 decreased ejection fraction (EF <55% for ≤54 yrs; or inversion) weighted images with increased <50% for >55 yrs); global systolic or diastolic function o Paroxysmal or sustained atrial or enhancement ratio between depression/abnormality; ventricular arrhythmias myocardial skeletal muscle o Ventricular dilation or wall thickness change o AV nodal conduction delays or involving ≥1 non-ischemic regional o Pericardial effusion intraventricular conduction defects distribution with recovery o Intracavitary thrombi 4 Cardiac symptoms: 5 Non-specific symptoms: 6 Infant/child non-specific symptoms o Acute chest pain or pressure o Fatigue o Irritability o Palpitations o Abdominal pain o Vomiting o Dizziness / syncope Dyspnea after exercise or lying down Poor feeding o o Edema o o Diaphoresis o Cough o Tachypnea o Sudden death o Lethargy .