Phew, almost had to drop this manga since it seemed like some heretics were trying to spread falsehoods about how 先輩 (senpai, for you plebs that don't know how to use google-sensei, unlike me) should be pronounced.
This is probably the first time I've seen any anime/manga translation group render 'dokidoki' as 'heart attack'.
I mean, yeah, MCs get super flustered, but calling it a 'heart attack'? That's a bit extreme.
And yes, I get that it's not super serious business.