A client who has anorexia nervosa (AN) with associated purging behaviors presents to the emergency department with dizziness and syncope. The client's vital signs are temperature 98.3° F (36.8° C), heart rate 52 beats/minute, respirations 21 breaths/minute, and blood pressure 79/41 mm Hg. A specimen for serum electrolyte levels is obtained with an electrocardiogram (ECG) pending. Which result should the nurse expect to see on the ECG?