Implications of late morphology of Braunwald-Cutter mitral heart valve prostheses

Interrelationships among silicone poppet wear, cloth wear, and tissue ingrowth were investigated in 14 retrieved Braunwald-Cutter heart valve prostheses following implantation of 37 to 118 (mean 83) months. Six aortic valves (mean 81 months) had severe cloth and poppet wear. In three the poppet had escaped. The lesser wear of the strut covering on the eight mitral valves (mean 84, range 37 to 108 months) was generally functionally insignificant. Mean decrease in mitral poppet diameter was 0.4% (range 0% to 1.5%), in contrast to a mean of 5.8% for aortic poppets. Histologic examination of the cloth/tissue complex demonstrated well-collagenized tissue ingrowth in areas of intact fabric with focal endothelial lining. Functionally trivial calcific deposits were often noted deep in the tissue coating, adjacent to cloth fibers or the strut metal. These results suggest that the mitral Braunwald-Cutter prosthesis need not be electively replaced without specific indication. A model is presented which explains the favorable clinical course demonstrated for mitral recipients and provides a rationale for the disparate clinicopathological behavior of mitral and aortic Braunwald-Cutter prostheses. Although inconsequential in this setting, the focal microcalcification noted in all mitral prostheses implanted for more than 72 months may have implications for the development of clinical cardiac assist devices for long-term application.