The heart was buried separately from the person
Body transportation was a very hard thing to do in the past. But what were you supposed to do if someone asked to be buried in an important and faraway place for them? In the 10th century, people came up with an idea to cut hearts out and bury them somewhere where they couldn’t bury the person.
Only the wealthy could afford this. Among the people who did this are Anne Boleyn, Richard I, and Frédéric Chopin.