Respiratory Arrest and Cardiovascular Collapse in a Young Autistic Woman

This is a 28 year old female with history of autism and seizures who suffered a respiratory arrest at home after a short febrile illness. She was found unresponsive in bed at 14:00 by her parents who initiated mouth to mouth ventilation. The paramedics arrived 10 minutes later and performed endotracheal intubation and ventilation. Her pulse was weak, her blood pressure was 60/40 mm Hg, and her core temperature was 31.0 °C.

Personal antecedents: She is adopted, and we have no information of the biological family.
Although she had a history of seizures as a child, she was not taking any medication when she suffered the respiratory arrest.
Her initial ECG is shown in the next slide. She was started on vasopressors and transported by helicopter to the hospital.
She received intravenous fluids, norepinephrine, vasopressin, and was slowly rewarmed with thermal blankets. After blood cultures, cefepime 2 grams was given intravenously for possible sepsis. Drug screening was negative. The only blood test abnormality was a low potassium of 2.9 mm/L. Head CT showed diffuse cerebral edema with effacement of the sulci and basilar cisterns, and ventricular compression without uncal transtentorial downward brain herniation. Her brain function has not improved after 3 days of medical support. The second ECG was preformed 1 day later.

Questions

1. How do you explain the abnormality observed in the initial ECG? 2. Why did the QRS normalize in the second ECG?
3. What are the following diagnostic steps?