A 72 year old female with a history of diabetes mellitus and no history of heart disease presents to the emergency department with chest pains at rest intermittently for the past 4 hours. She has associated shortness of breath and diaphoresis. Her heart rate is 59, blood pressure 134/72, respiratory rate 20, and oxygen saturation 95% on room air. Physical examination reveals normal lung sounds and an S4 gallop. Her ECG reveals ST segment depression in leads V1 to V3. She is given aspirin immediately. Her troponin levels remain negative. She is currently chest pain free.
Which of the following is the correct diagnosis?
A. Stable angina
B. Unstable angina
C. Non-ST segment elevation myocardial infarction
D. ST segment elevation myocardial infarction