Just because it doesn't make sense physiologically doesn't mean it doesn't make sense culturally. the term heart, not necessarily meaning your physical heart, is often just a representation of a person's very inner being. In many cultures it's considered the epicenter of someone's compassion or goodness. It's not just in english, look at any of the romance languages and you have the same terms being used. It's pretty much just a homonym
there's no other term you can really change that to, and express the same meaning.
this is just the soon to be doctor in you showing itself lol. nothing wrong with that, but clearly this is something that would bother someone in the medical profession more than the average person