Apparently there is no such word. I had long thought that this was the word one would use in order to discuss feelings of deep distress, however I came across heart-rending in my reading today (which I had never heard of.) I looked it up and found that it has the definition that heart-wrenching would have Then I looked for heart-wrenching, and it wasn't even there. I decided to check the Internet, to see if it was just me who has this misunderstanding. Apparently I am not though, because I found lots of documents that contain it.