There are a few previous threads on this topic which may be of interest to you:

http://www.reddit.com/r/AskHistorians/comments/12lw9s/when_did_the_heart_become_associated_with_love/

http://www.reddit.com/r/AskHistorians/comments/1fitq1/when_where_and_why_did_the_heart_become_the/

Not exhaustive, though!