One of the major design considerations of any object to be implanted in the body is the choice of materials.  Those used must be able to withstand the harsh and corrosive environment of the body, they must be inert, and they must be biocompatible so they do not elicit a rejection response. 

Particularly in heart valves, factors to consider are: how will the material impact hemodynamics, will it cause platelet aggregation or thrombosis, will the device damage blood cells, and are the mechanical properties sufficient to withstand the repeated cycles the valve will encounter in its lifetime.

Many different materials are used in the creation of artificial heart valves.  Metal alloys consisting of stainless steel or titanium are often used to give mechanical strength and for their corrosion resistance properties.  The struts on some leaflet valves and the cage on caged-ball models are commonly made of metal alloys due to their strength and durability requirements.
 
Pyrolytic carbon is another valuable material for its strength and its ability to prevent clotting.  This material has a similar structure to graphite and was originally developed for applications in the nuclear fuel industry as a coating for nuclear fuel particles.  However, it was soon realized that pyrolytic carbon had biomedical applications.  It is biocompatible, thromboresistant, resistant to wear, and has high strength and durability. It is able to stand up to the repeated opening and closing cycles it must endure when used in a mechanical heart valve.  It is commonly used for the inner orifice and the leaflets of bileaflet valves. The ATS Bi-leaflet valve shown here has leaflets made of pyrolytic carbon.

A material often used for the suture ring (which is used to attach the valve to the body) is Dacron. Dacron is a long chain polyester made from ethylene glycol and terephthalic acid. It is a synthetic fiber that has many uses in industry, including thermal insulation and sails for boats.  In biomedical applications this material is also commonly used for vascular grafts.  It is relatively inert and its porosity allows tissue in growth.

Another material that is commonly used for the suture ring is Teflon.  Teflon is used in many medical applications because of its signature low coefficient of friction. Teflon is relatively inert and highly biocompatible. As with Dacron it is often used for vascular grafts.