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A comparison of wear patterns in vivo and in vitro for Björk-Shiley Delrin heart valve discs.

MATERIALS AND METHODS
Wear patterns for 33 explanted Björk-Shiley Delrin heart valve discs with known implant durations were compared and contrasted with the wear patterns for 17 discs from accelerated wear tested (AWT) valves. Previous test reports and the current study provided data for the maximum depth of wear grooves for a total of 56 explanted BSD valve discs with implant durations up to 22.4 years.


RESULTS
The discs of the explanted BSD valves showed, in general, more than one type of wear pattern. Eighteen out of 33 exhibited a full indent groove on the inflow side and 24 of the 33 discs showed well indents on the outflow side. Only two discs showed evidence of non-concentric edge wear. All maintained their original surface polish outside of these areas. The data indicated that wear patterns in the case of the AWT discs were more pronounced, and in some discs were different in type from those of discs from explanted valves. For example, no cracks, fractures or perforations of the Delrin discs were observed, or reported, for the explanted valves, while in the 17 AWT valves there were three cracked discs, four disc fractures, three disc well perforations and three perforating edge indents.


CONCLUSION
It appears that the Shiley AWT conditions were more severe and imposed greater loads than those produced by patients with BSD valves implanted.