The role of T-peak to T-end, T peak–to–end/corrected QT ratios, and index of cardiac electrophysiological balance in the differential diagnosis of myocarditis

Aim: Paediatric myocarditis, a rare inflammatory cardiomyopathy (incidence 1–2/100,000 annually), challenges emergency diagnosis due to nonspecific symptoms mimicking common illnesses. This study assessed electrocardiographic markers of ventricular repolarisation heterogeneity—T-peak to T-end interval, T-peak to T-end/QT, T peak–to–end/corrected QT ratios, and index of cardiac electrophysiological balance—for diagnosing myocarditis and predicting ventricular arrhythmia risk in children aged 0–18 years. Methods: Retrospective case–control study of 76 myocarditis patients (diagnosed by clinical, laboratory, echocardiographic, and cardiac MRI criteria) presenting to our paediatric emergency department from January 1, 2024, to May 30, 2025, versus 75 age-matched healthy controls. Electrocardiographic parameters were measured in leads DII and V5. Receiver operating characteristic analysis evaluated the diagnostic performance of T-peak to T-end and T peak–to–end/corrected QT (Lead II (Derivation II)). Myocarditis cases stratified by arrhythmia development (with: n = 28; without: n = 48); groups compared via t -tests, Mann–Whitney U , and chi-square ( p < 0.05 significant). Results: Myocarditis group: 23 females (30.2%) and 53 males (69.8%); mean age 12.0 ± 4.7 years. Controls: 39 females (52.0%), 36 males (48.0%); mean age 10.3 ± 4.9 years ( p = 0.03). Receiver operating characteristic (Lead II (Derivation II)): T-peak to T-end cut-off 62 ms (sensitivity 69.3%, specificity 78.9%, area under the curve 0.725, p < 0.001); T peak–to–end/corrected QT cut-off 0.19 (sensitivity 50.7%, specificity 78.9%, area under the curve 0.625, p < 0.05). The arrhythmia subgroup showed corrected QT prolongation (470 vs. 435 ms, V5; p < 0.001), T-peak to T-end (110 vs. 90 ms, V5; p < 0.001), higher T peak–to–end/corrected QT, and index of cardiac electrophysiological balance (both p < 0.05). Conclusion: The T-peak to T-end interval, T peak–to–end/corrected QT ratio, and index of cardiac electrophysiological balance provide high-specificity, noninvasive electrocardiographic biomarkers for paediatric myocarditis diagnosis in the ED. Corrected QT and T-peak to T-end prolongation signals repolarisation heterogeneity and arrhythmia risk, supporting routine triage integration for early risk stratification.