An 11-year-old boy with autism and focal idiopathic epilepsy presented to the emergency department at an outside hospital after sudden onset of recurrent vomiting. He was nonverbal at baseline and unable to endorse any symptoms. His mother denied any fevers, upper respiratory infection symptoms, or shortness of breath. The patient’s seizures had been well controlled for the past 5 years on his current dose of levetiracetam, and he had not been on any other anticonvulsants. Telemetry at the emergency department revealed intermittent recurrent episodes of polymorphic ventricular tachycardia and ventricular fibrillation (Figure 1), which were terminated after multiple shocks were delivered. An intravenous bolus of 7.5 mg/kg of amiodarone was given, and the patient was transferred to the cardiac intensive care unit at our hospital for further workup. A 12-lead ECG was recorded on arrival to the cardiac intensive care unit (Figure 2). Echocardiography revealed a structurally normal heart. Troponin and electrolytes were normal. On the basis of the ECG, what is the most likely diagnosis?