This might be different than the others advice, and I don't know what your doctors have told you to do and when to call them, but what we have always done for Justin, after the first couple months post op, is to call his ped/GP for high temps and when he seems sick (Justin also has a history of BE, so I understand the fear of getting it again) and THEN if the blood cultures grew postive then we would call the cardiologist. I also usually don't take him to the ER for fevers, unless he is really sick, because his docs and me think ER waiting rooms are full of sick poeple with germs, so if possible we try to go to his doctor and avoid the ER. For a fever, we try to bring it down with tylenol ect if he gets it in the middle of the night, which he usually does.
Do you know what blood tests the ER ran? I am hoping if you were concerned about BE they drew blood cultures, since that is the test that would show if you have bacteria in your blood. What other sysptons are you having? There is alot going on this time of year, HOPEFLLY it is not BE
Now IF there is something I am pretty sure is heart/surgery related, like he had that weird thing on his incision a couple weeks ago, (he also has a history of a sternal infection) I WILL call his card or surgeon, because I know his ped will just tell us to have cardiology check him. One time I was almost positive he had BE, he had all the symptons, fever ect he did when he had BE, I was so surprised when the blood work showed Mono. (editted to add we did go to the ped and he orderred all htte blod work, including BE and Mono)
I hope your docs call you back soon and you start feeling better and can enjoy the holidays.