Review Question - QID 213200

A 64-year-old man presents to the emergency department with acute onset of chest pain. He says the pain is substernal and radiates to his left arm. He has a history of hypertension, diabetes mellitus, erectile dysfunction, benign prostate hyperplasia, and panic disorder. He takes aspirin, lisinopril, metformin, sildenafil, prazosin, and citalopram. An electrocardiogram shows new ST-elevations in the lateral leads. He undergoes catherization, which reveals a complete blockage of the left circumflex artery. A stent is placed, and the patient is discharged with clopidogrel and isosorbide mononitrate. Five days later the patient presents to the emergency department complaining of fainting spells. The patient’s temperature is 97°F (37.2°C), blood pressure is 89/53 mmHg, and pulse is 90/min. Physical examination is unremarkable. An electrocardiogram reveals lateral Q waves without ST or T wave abnormalities. Which of the following is the most likely cause of the patient’s presentation?