Meaning of stabbed/thorny/flaming hearts in religeous art

The Faithful of this world have produced some very weird art attempting to portray concepts of the Bible, and I know Cecil has already commented on Halos.  What I am curious about are the strange floating hearts which are sometimes painted on Jesus’ and Mary’s chests, outside of their bodies or foating nearby.  One I saw recently with Mary depicted a heart that was encircled with thorns, stabbed through with a sword and with flames
leaping gleefully from the top!  Now the thorns I suppose to represent Jesus, but swords, and FLAMES?  Mary was pointing at the heart and holding up her other hand in what looked for all the world to be a Boy Scout salute. Even being Catholic doesn’t help me understand what this is supposed to represent, can anyone?

That is “The Sacred Heart of Jesus”. I don’t know if this helps, but here’s the old Catholic encyclopedia trying to describe devotion to the Sacred Heart

When Catholicism reached south america, this is what you got. The image of the dissembodied heart was common among native religions. As locals were converted, many of the images of traditional religion were kept and adapted to Catholicism. At different times there has been significant controversy within the church concerning that imagery and suppressing it within south america.

The real history of it is considerable more complex than I just laid out, but it should get you looking in the right direction if you want to persue it further.

A history of devotion to the Sacred Heart of Jesus:

No mention that South America had anything to do with the origin of the icongraphy.

The sacred heart did exist long before Catholicism went to South America. That rendition where the heart is very central to the image and is “tortured” in a surprisingly explicit and brutal way displays the influence that I speak of.

Another image from the same time and place is the three headed or three faced Christ representing the trinity. This was similarly controversial and sometimes surpressed by the church.