Electrocardiographic Spectrum and Arrhythmia Profile in Children with Clinically Suspected Myocarditis: A Two-Year Prospective Observational Study from a Tertiary Care Center in Pakistan

Objectives: Pediatric myocarditis is an uncommon but potentially life-threatening inflammatory disease that frequently presents with nonspecific clinical manifestations, leading to delayed diagnosis. This study aimed to evaluate the spectrum of electrocardiographic (ECG) abnormalities and sustained arrhythmias in children with clinically suspected myocarditis and to identify electrocardiographic predictors associated with arrhythmia development. Methodology: This prospective observational study included a total of 106 consecutive children aged 1 month to 12 years with clinically suspected myocarditis. Standard 12-lead ECGs were obtained at admission and every 12 hours during hospitalization in addition to continuous cardiac monitoring. Sustained arrhythmias were classified as tachyarrhythmias or bradyarrhythmias, and patients were categorized according to the occurrence of sustained arrhythmias. Results: Among the 106 enrolled children, 68 (64.2%) were male, with a mean age of 5.4 ± 4.1 years. ECG abnormalities were identified in nearly all patients. Sinus tachycardia was the most frequent finding (96.2%), followed by ST-T abnormalities (49.1%), low-voltage QRS complexes (38.7%), premature atrial or ventricular complexes (18.9%), PR interval prolongation (14.2%), and QRS prolongation (11.3%). Sustained arrhythmias developed in 27 patients (25.5%), predominantly within the first 72 hours of admission. Tachyarrhythmias accounted for 70.4% of sustained arrhythmias, whereas bradyarrhythmias comprised 29.6%. Children with sustained arrhythmias had significantly longer hospital stays (19.5 ± 5.2 vs. 13.5 ± 4.1 days; P=0.002) and a significantly higher prevalence of ST-T abnormalities (85.2% vs. 36.7%; P=0.004). Multivariable logistic regression demonstrated that ST-T abnormalities independently predicted sustained arrhythmia (adjusted OR 9.85; 95% CI: 1.82–53.12; P=0.008). Conclusion: Electrocardiographic abnormalities are almost universal among children with clinically suspected myocarditis, and approximately one-quarter develop sustained arrhythmias during hospitalization. ST-T abnormalities are strongly associated with subsequent sustained arrhythmia and may facilitate early risk stratification. In settings where advanced diagnostic modalities are unavailable, systematic serial ECG monitoring during the first week of admission represents a practical and valuable strategy for early identification of high-risk pediatric patients.