Biomedical Engineering Reference
In-Depth Information
Figure 21.11.
Thrombus deposits on the material surfaces during the
in vivo
blood compat-
ibility experiments. The coated surface is seen to have marginally lower areas of thrombus
deposits. (See color insert.)
cooled to 30 ° C
2 ° C. The heart was arrested using electrical fi brillation. The
native mitral valve was excised and the artifi cial valve is implanted using 12 to 16
interrupted mattress sutures. Heart was closed and animal warmed back to 38 °C
before terminating the CPB. Post-operatively, the animals were administered
with anti-platelet drugs during the fi rst two weeks for reducing platelet aggrega-
tion and deposition. No anti-coagulants were given during the post-operative
period.
A total of 15 animals were implanted with ten test valves and fi ve control
valves. Test valves were made of Ti6Al4V cage coated with TiN, UHMWPE disc
and polyester sewing ring. The TTK-Chitra heart valve incorporating Haynes-25
alloy cage, UHMW-PE disc and polyester sewing ring was chosen as the control
valve. Animals were sacrifi ced at predefi ned time periods (Four test valves and
two control valves after three months of implantation and similar number of
valves at six months of implantation) to assess the healing around the valve and
for carrying out detailed histopathological analysis.
The explant analysis of the valves showed that the tissue in growth into the
valve orifi ce area was much less in the case of TiN coated model (see Figure
21.12). Other than this, both test and control valves healed very well and were
found to be well integrated to the anatomical site. There were no structural dys-
function or other valve related complications in any of the animals.
The results from these studies correlate well with the literature on tissue,
blood, and cytocompatibility of TiN and DLC coatings reported by different
investigators. The good blood compatibility of DLC coating is attributed to its
hydrophobicity and ability to take an excellent surface fi nish, resulting in a high
albumin deposition compared to fi brinogen deposition (Tsyganov et al., 2004;
Sweitzer et al., 2006; Huang et al., 2003). In the case of titanium nitride coatings, it
is postulated that the signifi cantly lower interface tension between titanium oxide
±
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