Idiopathic right ventricular outflow tract ventricular tachycardia-induced cardiomyopathy masquerading as MIS-C-associated myocarditis in a child.

Abstract

A previously healthy early adolescent male presented with respiratory distress and lethargy during the COVID-19 pandemic. Evaluation revealed ventricular tachycardia (VT), hepatomegaly, pleural effusion and cardiomegaly with impaired cardiac function. Positive COVID-19 antibodies suggested Multisystem Inflammatory Syndrome in Children (MIS-C)-associated myocarditis. Treatment with intravenous immunoglobulin, anti-inflammatory agents and amiodarone led to normalised cardiac function and arrhythmia resolution. However, VT recurred with myocardial dysfunction after stopping amiodarone. Further ECG reassessment identified focal VT originating from the right ventricular outflow tract (RVOT). Cardiac magnetic resonance showed no myocardial scarring, supporting the diagnosis of idiopathic RVOT-VT. Radiofrequency ablation was performed successfully, and the patient remained VT-free at 1-year follow-up. This case describes the rare presentation of idiopathic RVOT-VT causing cardiomyopathy, initially mimicking myocarditis. It highlights the limitations of current diagnostic modalities in distinguishing VT-induced cardiomyopathy from myocarditis and emphasises careful ECG and imaging evaluation to guide appropriate management and improve outcomes.