Review Question - QID 212474

A 35-year-old man presents to the emergency department for evaluation of weakness. He states that he has a history of alcohol use disorder, and has been drinking over the past several days with little food intake. He denies any pain, shortness of breath, or any other symptoms. He has no other significant past medical history and takes no medications. His temperature is 98.6°F (37.0°C), pulse is 90, blood pressure is 100/65 mmHg, and respirations are 16/min. Exam reveals a tired appearing man with dry mucous membranes noted. As he is being assessed, a rhythm change is noted on the cardiac monitor as shown in Figure A. Which of the following is the most likely cause of this patient's electrocardiogram findings?