After the Papercraft Torso and Heart with Interior Subdivisions Paper Model, Horst Kiechle released this improved paper Heart. This version uses a new system. Curved segments connect with tabs - Ribs on the inside guarantee strength and precision. If printed out without scaling it will produce a larger than life-size heart which is more comfortable to assemble.
You can download the papercraft model here: Anatomical Model - Improved Paper Heart Free Papercraft Download