Cusp disruption by massive lipid infiltration

A 68-year-old man underwent reoperation because of severe incompetence of a mitral valve xenograft, 96 months following implantation. Gross examination of the device showed yellow spots on the cusps, suggesting lipid infiltration, and a torn commissure. Plasmatic cholesterol and lipiprotein levels were normal. X-ray examination of the explants showed no calcific deposits. Histologic and electron microscopic studies disclosed massive accumulation of lipid clefts and droplets, predominantly at the level of the tear; focal loss and detachment of the endothelial lining and scanty porcine fibroblasts and collagen bundles with preserved periodicity were also noted. Primary disruption of porcine valvular bioprostheses without significant calcifications or collagen breakdown is uncommon. In the present case, lipid accumulation was the main determinant of tissue failure.