Very stunning piece, it is symmetrical with a hint of assymetry. The different use of dithering on the vessles to the heart makes the different textures shine through and increases the effectiveness of the small space used. The white outline helps to make the transition into transparency and blends it in to the background. The colours are a very good choice and are true to life. To improve the piece maybe another colour on the main section to increase the contrast a bit more and maybe a tiny bit more rounding on the edges to make it seem more organic.
Overall it is very effective and the techinques used are very good for such a small piece and still representing realism. Good stuff