Review Question - QID 216589

A 64-year-old man presents with nausea, vomiting, and weakness. He states that his wife made him come in when he fainted today while attempting to stand up. He otherwise states he has noticed some visual changes, including noting a yellow tint to objects. He has a history of heart failure with reduced ejection fraction, obesity, diabetes, hypertension, acute coronary syndrome, atrial fibrillation, and peripheral vascular disease. His temperature is 98.5°F (36.9°C), blood pressure is 153/91 mmHg, pulse is 40/min, respirations are 15/min, and oxygen saturation is 97% on room air. Physical exam reveals a frail man who is unable to ambulate secondary to lightheadedness. His neurological exam is otherwise non-focal. An ECG is performed as seen in Figure A. Which of the following is the most likely etiology of this patient’s symptoms?