This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
A 70-year-old man with a prior anterior MI comes for his routine evaluation. He feels well and has no symptoms. He is taking metoprolol 100 mg bid, aspirin 81 mg od, enalapril 10 mg bid, and simvastatin 40 mg od for secondary prevention.For the above patients, select the characteristic ECG finding. 
Select and explain. 
A. prolonged PR interval, B. broad-notched P wave in lead II, C. short QT interval, D. short PR interval
A: prolonged PR interval
Answer: A: prolonged PR interval 
Explanation: A prolonged PR interval is a common finding in asymptomatic elderly patients that have age-related degeneration of the AV node. Drugs such as beta-blockers (metoprolol) may exacerbate the condition or even cause PR prolongation in excessive doses.