Review Question - QID 216625

A previously healthy 15-year-old boy presents to the emergency department in cardiac arrest. He was in class when he suddenly fainted and became unresponsive. His teacher began chest compressions and he has received epinephrine and defibrillation from paramedics while in transport. On arrival, the patient remains pulseless and is pronounced dead. An autopsy is performed and is notable for no clear abnormalities. The patient’s laboratory studies were unremarkable from a visit to the pediatrician 3 weeks ago. A previous ECG is seen in Figure A. Which of the following is the most likely underlying etiology of this patient’s death?