Artificial Organs 19(9):921-927, Blackwell Science, Inc., Boston 0 1995 International Society for Artificial Organs Evaluation of Tilting Disc Valves after Fatigue Life Testing: Preliminary Results within a Comparison Program Vincenzo Barbaro, Giovanni Boccanera, Carla Daniele, Mauro Grigioni, and Alessandro Palombo Laboratory of Biomedical Engineering, Istituto Superiore di Sanita, Rome, Italy Abstract: A fatigue life test, by accelerating the beat rate, simulates several years of virtual life of a prosthetic heart valve in a short period of time. The correlation between the in vivo life of a valve and in vitro testing expectations is as yet not well established, but reproducible test con- ditions yield precious information about wear and failure. The paper reports a qualitative analysis of mechanical valve wear as part of a comparison program designed to investigate the significance of fatigue testing with the ul- timate aim of defining standard guidelines for these type of tests. Two tilting disc valves (29 mm) were subjected to 16 years of fatigue life simulated by means of a Rowan Ash fatigue tester (accelerated rate of 1,200 bpm). Fa- tigue-induced effects on valve disc and ring surfaces were observed under a monitor microscope to identify wear sites and patterns. A high speed cinematographic system was used to investigate the mechanisms responsible for the wear (wear modes). Valve closure was inspected at a 6,000 frame/s rate. Because of disc rotation during the tilting movement, the points of contact between disc and ring are distributed all around the disc edge but focally on the ring. On both sides of the disc, the surfaces present ring-like concentric grooves. After 16 years of fatigue life the valves showed neither severe wear nor alteration of their fluidodynamic behavior in the pulsatile flow test. Key Words: Prosthetic heart valves-Long-term durability-Fatigue life-In vitro testing-Motion analy- sis. Long-term durability of prosthetic heart valves is assessed by means of fatigue life testing by which several years of fatigue life can be accumulated in a brief period of time with accelerated beat rate ap- paratuses (1). No strict correlation has as yet been established between the in vivo life of a valve and its acceler- ated in vitro life. With bioprostheses, in vitro failure mode data are quite close to in vivo findings (2). For mechanical valves, various wear models have been developed to relate in vitro and in vivo wear data which showed that in vitro test conditions are much more severe than in vivo conditions (3). It is gener- ally accepted that long-term durability testing of mechanical prostheses is a useful tool to improve and to compare valve designs or to identify prob- lems associated with the manufacturing process. From a standardization viewpoint though, fatigue life testing of mechanical valves must necessarily lead to in vitro comparability which, in turn, de- pends strongly on the test conditions imposed on fatigue testers. In view of these considerations, an in vitro com- parison program within IS0 requirements has been implemented at the Laboratory of Biomedical En- gineering to study valve long-term behavior and to investigate the significance of fatigue testing within the process of standardization of prosthetic heart valve assessment. The comparison program applies to a common valve model for test combinations between testers and fluid media, which replicate the conditions adopted by different research centers and manufac- turers* The program contemplates the following phases: Received September 1993; revised November 1994. Presented in part at the 9th World Congress of the Interna- tional Society for Artificial Organs, held July 4-8, 1993, Amster- dam, The Netherlands. riore di Sanita, Wale Regina Elena 299, Rome, Italy. (a) fatigue testing for which basic test conditions are FTS300 (UK) (5); fluid medium: water or water and Address correspondence and reprint requests to Dr. Mauro Grigioni, Laboratory of Biomedical Engineering, Istituto Supe- fatigue testers: Rowan Ash (UK) (4) Or Shelhigh 921