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
Three weeks after surgery to implant a mechanical aortic valve, a 70-year-old man develops chest pain, fever, and leukocytosis. On examination, the JVP is increased, there is a mechanical S2 sound, and a pericardial friction rub. Which of the following is the most likely diagnosis? 
Select and explain. 
A. infection in the aortic valve, B. post pericardiotomy syndrome, C. cytomegalovirus (CMV) infection, D. pulmonary embolism
B: post pericardiotomy syndrome
Answer: B: post pericardiotomy syndrome 
Explanation: The principal symptom is the pain of acute pericarditis that usually develops 1-4 weeks following the cardiac surgery but could appear after months. It can also occur after myocardial infarction (Dressler's syndrome) or after trauma to the heart (stab wound, blunt trauma). The syndrome can remit and recur for up to 2 years. The acute symptoms usually subside in 1-2 weeks.