Do you know anyone thats personality totally changed after heart surgery?

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i have been told its common but havent known anyone other than my dad it happened to.. his aorta started to split which would have caused instant death (that is what killed john ritter) but they caught it in time to replace the whole thing.. it was a true freak of nature thing that he went months with it slowly thinning which started in december but he went to the ER and they said he was fine but several months later they caught it on an mri and rushed him into surgery.. normal people it splits within seconds with no advance notice etc.. anyways my question is that after his heart surgery his whole attitude and personality has changed.. im not talking in the way that people that almost die start living for the day or anything but like totally bizarre.. he has episodes where he even seems intoxication but he doesnt drink nor does any of his meds cause that affect.. the doctors say its because they kept him under too long and he didnt want to wake up out of the coma later and that there could be brain damage or something.. i know a lot of people that have had a minor (well one had major) heart surgery but yet all of them were the same after as before.. are the docs wrong or could it be brain damage etc? they scanned his brain and it shows its fine.. my whole family find its hillarious because he was always uptight before it and now he is just humorous but i cant help but wonder if its wrong to enjoy the new him because it might be something else or something