In-Vitro Assessment of the Wear Development Mechanism and Stabilization of Wear in the Edwards MIRA/Sorin Bicarbon Mechanical Heart Valve Orifice Ring
Helmut Reul Dr-Ing, Christoph Schmitz Dipl-Ing, Ewald M. Pfaff Dr-Ing , Cornelia Hohlstein PTA, Paul A. Schmidt MS, Günter Rau Dr rer nat, Pietro Arru Dott Ing

This study presents a detailed morphological description of the early to middle (0 to 200 million cycles) stages of wear development in the Carbofilm carbon coating on the Edwards MIRA/Sorin Bicarbon mechanical heart valve housing (orifice ring) pivot slots. Wear testing was performed using a specially designed durability tester that controls impact loading. A morphological assessment was performed using light and scanning electron microscopy; this allowed qualitative and quantitative assessment of the nature and rate of Carbofilm removal. The wear showed first a gradual thinning of the Carbofilm layer in locations in contact with the leaflets, followed by small areas of film removal, culminating in slowly increasing areas of exposed titanium alloy substrate. The process is not one of ÔflakingÕ or spalling of relatively large particles. The exposed titanium alloy surface is typically smooth and burnished. The wear rate is well behaved, stabilized by approximately 40 million cycles, with the wear area expansion rate continuing to decrease up to 200 million cycles.