Review Question - QID 214837

A 67-year-old woman with a past medical history of heart failure, atrial fibrillation, hypertension, diabetes, gout, and bipolar I disorder presents with nausea, vomiting, and syncope. The patient can recall no sick exposures, recent travel, or medication changes other than over-the-counter medications for some knee pain she has had. She does not smoke and rarely drinks alcohol. She complains of changes in her vision as well. Her temperature is 98.1°F (36.7°C), blood pressure is 72/53 mmHg, pulse is 33/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam reveals a frail woman with dry mucous membranes and muscle wasting. An EKG is performed as seen in Figure A. Which of the following most likely contributed to this patient’s presentation?