This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Anaesthesia
A 55-year-old woman requires an abdominoperineal operation for rectal cancer. She has a history of stable angina. Which of the following clinical markers is most likely to predict a cardiac event during her noncardiac surgery and should prompt fuher cardiac workup prior to her operation? 
Select and explain. 
A. Abnormal electrocardiogram, B. Prior stroke, C. Unstable angina, D. Uncontrolled hypeension
C: Unstable angina
Answer: C: Unstable angina 
Explanation: The planned operation is a high-risk procedure.Patients can be stratified as having major, intermediate, or mild predictors of having a cardiac event. Major predictors include unstable angina, recent myocardial infarction, decompensated congestive hea failure, significant arrhythmias, and severe valvular disease. Intermediate predictors include mild angina, prior myocardial infarction, compensated or prior congestive hea failure, diabetes, and renal insufficiency. Minor predictors include advanced age, abnormal electrocardiogram, irregular rhythm, poor functional capacity, prior stroke, and uncontrolled hypeension.