A 42-year-old construction worker with a medical history of diabetes, hypertension, and tobacco use presents to the emergency department with two weeks of chest pain that radiates to his left arm. The pain used to occur with exertion but now occurs even at rest. An electrocardiogram is obtained that does not demonstrate any ischemic changes. Cardiac biomarkers are obtained which are negative. What is the most likely diagnosis? Unstable angina. ST-segment elevation myocardial infarction. Non-ST-segment elevation myocardial infarction. Stable angina. Aortic dissection.