A 56-year-old man presents to the emergency room with nausea, vomiting, muscle cramps, and weakness that began three days ago. He started Penicillin G for acute pharyngitis five days ago and has been taking it regularly along with lisinopril, atorvastatin, and spironolactone. On examination, he appears anxious, has difficulty walking, and shows decreased sensations and reflexes in all four extremities. Laboratory studies reveal a potassium level of 6.8 mmol/L, and his ECG shows changes consistent with hyperkalemia. If his hyperkalemia progresses without treatment, what is the most likely cause of death?
