Polymer heart valves

Since the introduction of valve replacement surgery, research has aimed at creating a prosthesis that is safe, durable and effective. Neither of the t wo broad groups of valve currently available is ideal, A prosthetic valve i s needed that does not suffer from the known disadvantages of calcification and premature failure (bioprostheses), and thrombogenicity (mechanical val ves). Much progress has been made, both in design and materials, and an ext ensive range of polymer valves has been produced and tested both in vitro a nd in vivo. Unfortunately, each stage of development has encountered proble ms preventing successful clinical application. Many design difficulties hav e been addressed and potentially reduced to acceptable levels, but calcific ation remains a problem, although much less so than with bioprostheses. New developments in surface modification may hold the key to the elimination o f thrombus and calcification, and early in vivo results are promising. It i s likely that an effective and safe polymer valve will soon become a third clinical option. The historic aspects behind the development of polymer val ves and the current state of research and evaluation are discussed.