The following are key points to remember about this scientific statement from the American Heart Association on the diagnosis and management of myocarditis in children:

1. Myocarditis remains a clinical challenge in pediatrics. Four strata of certainty in the diagnosis of myocarditis include biopsy proven, clinically suspected confirmed by cardiac magnetic resonance (CMR), clinically suspected, and possible myocarditis.
2. Clinically suspected myocarditis represents a constellation of findings supportive of the diagnosis of myocarditis when biopsy and CMR cannot be performed or despite their negative results. To date, there are no definitive criteria using clinical features alone to confirm the diagnosis of myocarditis or to differentiate clinical suspicion from possible myocarditis.
3. Acute myocarditis commonly has an infectious cause, with viral causes being the most prevalent. Specific viral causes have been shown by polymerase chain reaction (PCR) analysis of myocardial tissue and have demonstrated that the prevalence of specific viruses has shifted over time from predominantly adenovirus and enteroviruses to parvovirus B19 and human herpesvirus 6. Noninfectious causes of myocarditis include autoimmunity, hypersensitivity, medications, and toxins.
4. Myocarditis presents as several distinct clinical profiles. Typically, acute myocarditis presents with a poorly functioning ventricle with or without dilation, recent heart failure symptoms, and viral infectious symptoms in the preceding weeks. Fulminant myocarditis presents as cardiogenic shock; tachyarrhythmias are common, and inotropic or mechanical circulatory support (MCS) may be needed. Chronic persistent myocarditis occurs in the setting of cardiac symptoms such as chest pain, often with preserved systolic function, and histologic evidence of persistent myocardial inflammation. There have also been reports of pediatric patients with recurrent myocarditis, defined as episodes of acute myocarditis with intervals of clinical resolution.
5. Echocardiography is the first-line and most widely used imaging modality for the evaluation of cardiac structure and function in patients suspected of myocarditis. Echocardiography reliably demonstrates the variable findings associated with myocarditis, including the following:
   • Subtle to profound changes in global left ventricular (LV) or right ventricular systolic function, including regional wall motion abnormalities
   • Variable degrees of LV enlargement
   • Thickened myocardium from wall edema
   • Pericardial effusion
   • Intracardiac thrombus
   • Functional valvar regurgitation
6. CMR can demonstrate markers of inflammation and necrosis that characterize myocarditis histologically. Beyond tissue characterization, CMR is the gold standard for quantification of ventricular volumes, ejection fraction, and mass.
7. Supportive care of myocarditis is similar to other scenarios of acute heart failure. Low cardiac output should be treated promptly. Milrinone typically is used as first-line therapy for inotropy, whereas inotropes with vasopressor properties such as epinephrine and dopamine are generally reserved for those with hypotension and cardiogenic shock because these agents have more chronotropic and arrhythmogenic potential.
8. Anticipatory care includes careful triaging and admission to a ward that can monitor the cardiovascular condition closely or transfer of the patient to a center that can provide advanced pediatric cardiovascular care, including MCS and transplantation.
9. Antiviral therapy should be considered if an active viral infection is found. Immunomodulatory or immunosuppressive therapy remains center and practitioner specific, and each center should develop its own multidisciplinary guidelines of care with ongoing review to ensure quality.
10. Finally, demonstrating the effectiveness of future therapies requires properly designed trials in which a prerequisite is a uniform and accepted working diagnosis.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Pericardial Disease, Prevention, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Antiviral Agents, Autoimmunity, Cardiac Output, Low, Chest Pain, Diagnostic Imaging, Dilatation, Dopamine, Echocardiography, Edema, Epinephrine, Heart Failure, Herpesvirus 6, Human, Hypotension, Inflammation, Magnetic Resonance Spectroscopy, Milrinone, Myocarditis, Myocardium, Pediatrics, Pericardial Effusion, Polymerase Chain Reaction, Primary Prevention, Shock, Cardiogenic, Tachycardia, Thrombosis, Ventricular Dysfunction, Virus Diseases

< Back to Listings