Problems of materials in mechanical heart systems.

C'rirretill>available inaterials for niechaiiical hear ,terns are siirveyed, particrilarly with respect to long-term implatitatioti, from the viewpoiiits of availability a i d workability, mechariical aiid biological durability, and compat ibility with hlocid and tissiie. Some materials have one or more desirable physical properties, hut tione off'ers perfect blood and t lie compatibility. 1Irdicd grade Siln.li(,, cotisidered best for blood hniidlitig parts, has prodriced proniisitig resrrlts i t i arisiliary ventricle patency rqxrimeiits. The insiifficierit tensile stietigth of Rilastic zhcirild be increased, arid it may be possible to accomplish this while maintnitiing the present resilience, elongation, and inertness. No long-term data on thrombriformat>ion are available, but clot-retarding quality is esseiitial and may perhaps be obtained by iiicorporat,ing heparin. Developmetits iti polymer chemi-t ry may also lead to other surfaces with the requisite mechanical properties with l)l(iOd.