Review Question - QID 214644

A 43-year-old man with a history of epilepsy and febrile seizures presents to the emergency department with malaise. He has been feeling worse over the past 3 days and now has a fever and chills. He admits to using heroin 1 week ago. The patient also admits to buying and using clonazepam from a local drug dealer. His temperature is 102°F (38.9°C), blood pressure is 110/74 mmHg, pulse is 110/min, respirations are 19/min, and oxygen saturation is 98% on room air. Physical exam reveals the finding in Figure A which is also noted on the patient's feet. The lesion is injected with a medication in preparation for a procedure, followed shortly by the patient demonstrating flexion and extension of his extremities with a lack of responsiveness. After the episode, the patient seems confused. His blood pressure is 90/64 mmHg, pulse is 40/min, respirations are 15/min, and oxygen saturation is 96% on room air. An ECG is performed as seen in Figure B. Which of the following is the most likely cause of this episode?