Monomorphic ventricular tachycardia in a child after arterial switch operation: Coronary ischemia or something else

Background Ventricular tachycardia (VT) in children following arterial switch operation (ASO) for dextro-transposition of the great arteries (D-TGA) is uncommon and typically raises concern for coronary artery compromise. However, alternative causes such as acute myocarditis may present with similar clinical and biomarker features, creating a diagnostic challenge in the acute setting. Case Report A 7-year-old boy with a history of D-TGA repaired with neonatal ASO presented with vomiting, palpitations, and lethargy. Electrocardiogram demonstrated sustained monomorphic VT at 220 beats/min. He remained hemodynamically stable. The arrhythmia did not respond to adenosine or lidocaine but terminated with amiodarone. Post-conversion evaluation revealed depressed left ventricular systolic function (ejection fraction 35%) and elevated troponin and NT-proBNP levels. Coronary computed tomography angiography demonstrated unobstructed coronary arteries. Cardiac magnetic resonance imaging showed elevated T1 and T2 values with subepicardial late gadolinium enhancement, consistent with acute myocarditis. The patient was managed with antiarrhythmic therapy, including amiodarone acutely followed by beta-blockade and mexiletine, along with intravenous immunoglobulin. Ventricular function improved rapidly, and no recurrence of VT was observed during hospitalization or early follow-up. Why Should an Emergency Physician Be Aware of This? In patients with prior ASO presenting with wide-complex tachycardia and ventricular dysfunction, coronary insufficiency is often the leading concern. This case highlights that acute myocarditis may mimic ischemia in this population. In the emergency setting, prompt recognition and appropriate antiarrhythmic selection, including escalation to amiodarone for refractory VT, are critical. Early use of advanced imaging can clarify the diagnosis, guide management, and avoid unnecessary invasive evaluation. Timely arrhythmia control may result in rapid recovery of ventricular function.