Mortality in children with fulminant myocarditis: a six-year multicenter retrospective study.

Background: Fulminant myocarditis (FM) in children can progress rapidly to cardiogenic shock, with high risk of mortality. Early recognition of prognostic markers is critical to guide timely escalation of circulatory support. This multicenter study sought to characterize clinical features and identify early predictors of in-hospital mortality in pediatric FM. Methods: We conducted a retrospective cohort study of patients <18 years with FM admitted to eight ECMO-capable pediatric intensive care units between January 2018 and August 2023. Clinical, biochemical, electrocardiographic, and echocardiographic variables were analyzed. Logistic regression was used to identify predictors of mortality, and receiver operating characteristic (ROC) curves were generated to assess discriminatory performance. Results: A total of 187 children were included; 157 (84.0%) required ECMO. In-hospital mortality was 16.6% (31/187). Univariate analysis identified elevated CK-MB, higher peak lactate, and ventricular tachycardia as associated with mortality. In multivariate analysis, peak lactate (AUC 0.791) and CK-MB (AUC 0.774) remained independent predictors. A combined model of peak lactate and ventricular tachycardia demonstrated moderate discrimination (AUC 0.772), whereas a composite model incorporating CK-MB, peak lactate, and ventricular tachycardia achieved the best predictive performance (AUC 0.815). Elevated lactate measured 12 h after initiation of extracorporeal membrane oxygenation or intensive conventional therapy further increased mortality risk (OR 1.219, 95% CI 1.004-1.481). Conclusion: Peak lactate, CK-MB, and ventricular tachycardia are early independent predictors of in-hospital mortality in pediatric FM. Persistent hyperlactatemia within 12 h of advanced support provides additional prognostic value and may assist clinicians in early risk stratification.