Why is the first lines of the Dhammapada twin verses sometimes translated using the word 'heart'?

In most of the translations of the Dhammapada I have read the first lines of the Twin Verses (first chapter) are rendered using the words mind or thoughts. For instance this translation by Buddharakkhita > Mind precedes all mental states. Mind is their chief; they are all > mind-wrought. However I recently read a translation by Thanissaro (in this book ) that renders the lines as > Phenomena are preceded by heart, ruled by heart, made of heart I found the variation from mind (or thoughts) to heart quite striking. What is the original Pali phrasing and which words are able to be translated freely between mind and heart? What is the overall sense of the Pali words used i.e. what are the nuances or subtleties to the original Pali?