delrin and Aortic-Valve-Insufficiency

A 39-year-old woman had undergone mitral valve replacement (MVR) (29-mm Björk-Shiley Delrin disk) at 6 years of age. Severe mitral regurgitation, aortic regurgitation, and left ventricular dilatation were detected by echocardiography in October 2006, and MVR (ON-X 25 mm) and aortic valve replacements (St. Jude Medical Regent, 21 mm) were performed in December. The Delrin disk of the previous prosthetic valve, located at the position of the mitral valve, was markedly abraded, broadening the clearance from the valve seat. The postoperative course was smooth without complications, and the patient was discharged, walking by herself, on day 19 after surgery. A Delrin disk was used for the tilting valve in early Björk-Shiley valves, but has been replaced by pyrolytic carbon because of problems with durability of the Delrin material. Follow-ups of patients who have undergone procedures using Delrin disks ares necessary, with consideration of valve replacement.

Topics: Adult; Aortic Valve Insufficiency; Device Removal; Female; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Humans; Mitral Valve Insufficiency; Prosthesis Design; Prosthesis Failure; Reoperation; Resins, Synthetic; Treatment Outcome

Wear of Björk-Shiley Delrin (BSD) heart valve discs is known to have occurred in some patients, possibly contributing to increased regurgitation. This paper specifically addresses surface and edge wear that have been observed on some discs of explanted BSD valves after implant durations up to 22.4 years.. The wear patterns have been documented using either photographic or scanning electron microscopic methods for 42 out of 73 explanted BSD valve discs. The remainder of the 73 discs were not available for analysis.. One form of surface wear found on 18 out of 42 of the Delrin discs was the concentric wear of mild abrasive origin along the surface near the disc edge due to contact with the inlet and outlet struts. In five instances, surface anomalies were observed, primarily in the areas of high velocity blood flow. This paper also describes two Delrin discs with non-concentric edge wear patterns: (a) one which appears 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 abnormal rotation of the disc during valve closure, and (b) a second one which is thought to have been caused by a cutting action of the knife-like stub of one inlet strut leg which had separated. Cross-sectional analyses of two explanted BSD discs, with full indent grooves on the inflow side, indicated that the Delrin material was primarily compressed under these wear grooves, rather than removed by abrasion. Hardness profiles indicated that the Delrin 150 microns below the surface was harder and would tend to prevent further deformation. A simple model describing the compound impact (impact with sliding) phenomenon is introduced to explain abrasive wear found on some explanted BSD discs.. Based on the studies here and reports in the literature, the BSD heart valve appears to present a design which provides many years of service and, when wear occurs, it occurs in a manner that provides easily recognized clinical symptoms, which allow time for diagnosis and treatment.

Topics: Aortic Valve; Aortic Valve Insufficiency; Heart Valve Prosthesis; Humans; Materials Testing; Microscopy, Electron, Scanning; Mitral Valve; Mitral Valve Insufficiency; Photography; Prosthesis Failure; Resins, Synthetic