| Synthetic Sapphire as an Artificial Heart Valve
Occluder-Promise and Problems* |
G. S. BHUVANESHWAR, C. V. MURALEEDHARAN,
G. A. V. LAL, A. V. RAMAN!
AND M. S. VALIA THAN
Pages : 87-92
DOI : 10.1080/0371750X.1991.10804498 |
| Abstract |
| A tilting disc artificial heart valve using a synthetic sapphire disc and
a titanium nibide coated Haynes alloy cage was developed. Sapphire
has proved to be an excellent biocompatible material in toxicology
testing. Functional evaluation in a pulse duplicator showed the valve
to be comparable in performance to the standard Bjork-Shiley valve.
It successfully completed the accelei'ated durability test as per
international protocol. In animal evaluation, the synthetic sapphire
disc fractured in S animals in a total of 14 implants. However, in all
the animal implants, sapphire has proved to be an excellent blood
compatible material.
Preliminary failure analysis of the sapphire fracture was carried
out by changing the assembly procedure, studies of crystal orientation
by transmission Laue X-ray diffraction photography of the failed and
intact discs and by indentation studies. High flow and high pressure
accelerated testings of the valves were carried out to induce fracture
in the in-vitro system so that the testing could be made more reliable
in terms of showing up failures before animal implantations were
carried out.
Though this work did not result in a successful product, it clearly
brought out the need for unde1standing the fracture mechanics of
ceramics and the ability to eliminate defective components before
using them in such critical devices like an artificial heart valve. |
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