I will guess a beta blocker, and I can say I know BB can have
dizziness, suppose even passing out, as an unwanted side effect. However, this is usually, in my experience, because BB lowers the BP too much, easy to fix, lower the dose.
I take BB to lower my HR, and get unwanted lower BP, which has caused some dizziness for me in the beginning, when I wen to high dose levels. I have grown out of that at this point.
I think it unlikely that a BB would cause any heart problems.