SURFACE AND EDGE WEAR OF BJORK-SHILEY DELRIN(R) HEART-VALVE DISCS

Background and aims of the study: Wear of Bjork-Shiley Delrin(R) (BSD) heart valve discs is known to have occurred in some patients, possibl y contributing to increased regurgitation. This paper specifically add resses surface and edge wear that have been observed on some discs of explanted BSD valves after implant durations up to 22.4 years. Methods : The wear patterns have been documented using either photographic or scanning electron microscopic methods for 42 out of 73 explanted BSD v alve discs. The remainder of the 73 discs were not available for analy sis. Results: One form of surface wear found on 18 out of 42 of the De lrin discs was the concentric wear of mild abrasive origin along the s urface near the disc edge due to contact with the inlet and outlet str uts. In five instances, surface anomalies were observed, primarily in the areas of high velocity blood flow. This paper also describes two D elrin discs with non-concentric edge wear patterns: (a) one which appe ars to be due to fatigue micro-chipping and abrasive wear of the disc of a 20 year BSD explant, which had fibrous tissue ingrowth, causing a bnormal rotation of the disc during valve closure, and (b) a second on e which is thought to have been caused by a cutting action of the knif e-like stub of one inlet strut leg which had separated. Cross-sectiona l analyses of two explanted BSD discs, with full indent grooves on the inflow side, indicated that the Delrin material was primarily compres sed under these wear grooves, rather than removed by abrasion. Hardnes s profiles indicated that the Delrin 150 mu m below the surface was ha rder and would tend to prevent further deformation. A simple model des cribing the compound impact (impact with sliding) phenomenon is introd uced to explain abrasive wear found on some explanted BSD discs. Concl usion: Based on the studies here and reports in the literature, the BS D heart valve appears to present a design which provides many years of service and, when wear occurs, it occurs in a manner that provides ea sily recognized clinical symptoms, which allow time for diagnosis and treatment.