At the time, I was quite uncertain about the material used. One commenter said that it was papercraft, and would appear to be correct.
I am told that the artist was a winner in a world karakuri contest back in 2005.
I see also that the artist has made a piece similar to the heart in the form of a cube. Video of the cube can be seen here if you have the right plug-in.
The artist, Haruki Nakamura, also does other forms of paper-craft including illustration, models, and impressive 3 dimensional tessellations.
See more from the artist on Haruki Nakamura's web site.
[ Thanks philsing and PINO! ]