Hi sigs! Absolutely he can have inflammation. There is a blood test where they test the level of something to see how bad inflammation is. Sorry I don't know the name but your Dr would know. I had open heart surgery and still several weeks after I couldn't breathe and had severe pain, Drs dismissed it and 3 weeks post surgery I was admitted with fluid surrounding my heart. This is pretty serious so keep an eye on it.
Good luck!
Yes it could occur even up to 6 months after open heart surgery. Typically, it is self limiting, but occasionally, medications such as nsaids, steroids or even colchinie may be used to help with the symptoms and toward faster recovery.