[Agrajag]

With the eyes you can maybe understand that they can insert themselves into the mage's eye without his consent, but the hearts' description explicitly says that the chest wound is the result of "crude surgery"
and not the heart implanting itself into the "victim", so unless the heart is also a surgeon and has appendages and at least some knives and a sewing kit, it's harder to imagine it flying into your chest.

EDIT: manually inserted a linebreak to improve readability since the thread has been stretched by an unruly link.