Unexpected Pediatric Cardiac Arrest in a Toddler

INTRODUCTION: Ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) are rare causes of pediatric out-of-hospital cardiac arrest (OHCA), especially in toddlers. Within VT, catecholaminergic polymorphic ventricular tachycardia (CPVT) is an uncommon but potentially fatal channelopathy that may present as collapse during emotional or physical stress. CASE PRESENTATION: A previously healthy 2-year-old boy collapsed during a tantrum and became pulseless. Dispatcher-assisted CPR was limited due to a lack of bystander training, but law enforcement arrived before EMS and initiated compressions. Upon EMS arrival, the patient was found in ventricular fibrillation (VF) and promptly defibrillated with a 70-J biphasic shock (~4 J/kg), achieving return of spontaneous circulation (ROSC). Intraosseous (IO) access was obtained, and 1 mg/kg lidocaine was administered. En route, the patient developed seizure-like activity, treated with IO midazolam. In the ED, the child was hemodynamically stable but intermittently irritable. He had a normal baseline ECG showing sinus tachycardia. He continued to display episodes of seizure-like activity-characterized by decerebrate posturing and limb rigidity-and was treated with lorazepam. Cardiology and PICU teams were consulted. After admission to the PICU, a transthoracic echocardiogram (TTE) revealed no structural heart abnormalities. An epinephrine challenge provoked bidirectional VT, consistent with catecholaminergic polymorphic ventricular tachycardia (CPVT). Genetic testing later confirmed a likely pathogenic RYR2 variant. The patient was discharged on propranolol and flecainide, with a loaner AED and outpatient follow-up arranged. CONCLUSION: This case highlights the vital role of prehospital defibrillation, rapid IO access, and recognition of seizure-like activity as a potential recurrent arrhythmia in pediatric VF arrest. While definitive diagnosis, including echocardiography and genetic testing, occurs in the hospital, early EMS intervention-particularly rhythm recognition and timely shock delivery-was lifesaving in this rare pediatric case.