This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Cardiac Biomarker of Choice for diagnosis of Re-infarction 8 days after the initial ischemic event is: 
Select and explain. 
A. Troponins, B. CK-MB, C. Myoglobin, D. LDH
B: CK-MB
Answer: B: CK-MB 
Explanation: Answer is B (CK-MB) CK-MB is the Cardiac Biomarker of Choice for diagnosis of Re-infarction 8 days after the initial ischemic event. The CK-MB level will increase approximately 4-8 hours after a myocardial infarction and return to normal after 72 hours (3 days). This makes it useful for the detection of re-infarction in the 4-10 day time window after the initial insult since troponins may remain elevated for 10-14 days making it less useful for this purpose.