Recent Trends in Incidence and Outcomes for Acute Myocarditis in Children in the United States

Objectives: Lack of defined diagnostic criteria for acute myocarditis makes its diagnosis dependent on clinical suspicion. The objective of this study was to the current trends in demographics, clinical manifestations, treatments, and outcomes in the United States for children hospitalized with acute myocarditis. Methods: This retrospective study was conducted using data collected from the Pediatric Health Information System (PHIS) database for the years 2014-2020. We included patients 21 years or younger with acute myocarditis. The statistical analysis was performed using Chi-squared and continuous variables using Mann-Whitney U-test for continuous data comparisons. Results: We found 1199 patients with acute myocarditis. About 60% of patients required admission to the intensive care unit (ICU). The median hospital length of stay was four days for all patients and six days for ICU patients. Two hundred sixty-five (22.1%) patients required invasive mechanical ventilation, 127 (10.6%) required Extracorporeal membrane oxygenation, 33 (2.8%) required Ventricular assist device and 22 (1.8%) required cardiac transplantations. Milrinone was the most used vasoactive agent. The overall hospital mortality was 2.3%. IVIG infusion use decreased during the study period. On multivariate analysis, vasoactive medication use, (p< 0.01) and arrhythmia (p = 0.02) were independently associated with increased odds of mortality. IVIG use (p=0.01) was associated with decreased odds of mortality. Conclusions: Despite high morbidity and frequent need for advanced life support measures, the survival outcomes of acute myocarditis in children are favorable. Vasoactive medication support and occurrence of arrythmia were independently associated with mortality, most likely due to disease severity. Administration of IVIG was independently associated with reduced mortality.