Subject selection
This study was conducted at Beijing Children’s Hospital, Capital Medical University. Inclusion criteria were (1) age less than 18 years old, (2) boys or girls, (3) clinically diagnosed pediatric myocarditis and (4) the acute stage in the clinical stage of myocarditis. The main exclusion criteria were as follows: allergy to Phosphocreatine Sodium, other causes of myocardial injury, a history of heart disease, other serious illnesses, other causes of electrocardiogram changes, participated in other clinical trials prior to screening and patients with renal insufficiency. The baseline information included gender, age (year), height (cm), bodyweight (BW, kg), disease duration, white blood cell count (WBC), red blood cell count (RBC), hemoglobin (HGB), blood platelet count (PLT), percentage of neutrophils (NEUT), lymphocyte percentage (LYMPH), percentage of monocytes (MONO), percentage of eosinophilic cells (EO), percentage of basophilic cells (BASO), total protein (TP), albumin (ALB), alkaline phosphatase (ALP), aspartate transaminase (AST), alanine transaminase (ALT), total bilirubin (TBIL), direct bilirubin (DBIL), urea, creatinine, uric acid (UA), creatine kinase (CK), creatine kinase-MB (CK-MB), lactic dehydrogenase (LDH), alpha-hydroxybutyric dehydrogenase (HBDH) and hypersensitive troponin -I (HSTN-I). The details of these clinical data characteristics are provided in the Supplemental Material 1. The glomerular filtration rate (GFR) for children older than 1 and younger than 18 was calculated using the creatinine-based “Bedside Schwartz” equation (currently considered the best method for estimating GFR in children) [13]. For children under 1 year old, the GFR was estimated using the original Schwartz equation [14]. This clinical trial protocol was approved by the Ethics Committee of Beijing Children’s Hospital (Approval number: [2016]-Y-013-C-02). Written informed consent was obtained from each enrolled patient or their legally authorized guardian.