It is a typical warm, sticky late summer afternoon when EMS arrives, transporting a 13-year-old boy to the emergency department (ED). The paramedics state they were called after he collapsed and had a syncopal episode with altered mentation while at football practice. On scene, he was found to be tachycardic with a heart rate between 180 to 200 beats/min. No other history was known. Thought to be in supraventricular tachycardia (SVT), adenosine 6 mg was given with no response. A repeat dose of 12 mg dose was given, also with no change. Cardioversion with 50 joules was then unsuccessful. The patient could not provide any further history as he was oriented to self only—mumbling but not conversive or appropriate. He was able to maintain his airway and subsequently transported to the ED.
Upon arrival, he was found to be persistently tachycardic (pulse, 180 to 190 beats/min), hypotensive (BP 99/72 mm Hg), and tachypneic (respiratory rate 32 to 36 breaths/min). Estimated weight was 100 kg. He was very slow to respond to questioning, able to say his name but little else. Gag reflex was intact. Glasgow coma scale (GCS) score was 15. His skin was cold and clammy and he was diaphoretic.
Adenosine was repeated and multiple attempts at cardioversion were unsuccessful. During cardiology evaluation, ECG revealed sinus tachycardia and the patient exhibited posturing of the upper extremities that progressed to a 2- to 3-minute generalized tonic clonic seizure. This resolves with 2 IV doses of lorazepam. He was given a loading dose of fosphenytoin (20 mg/kg).
What is wrong with this young man?