http://home.howstuffworks.com/quilte...ow-pattern.htm
I typed in "quilted hearts" ... perhaps the first ten links were businesses with that name, and this was the first link that came up with something "to do" ... if you want to do embroidery inside a heart, I think I would make the embroidery first, and then create a framing heart by cutting a template the thickness I want the frame to be, trace that frame onto double fusible webbing, fuse the webbing to the back of the frame, and then fuse the frame fabric on to the embroidery piece ...
the double fusible products sound as though they would be stiff, but I have used them in appliquing and it isn't hard to get a needle through the stuff ... it really is quite supple.