Pathological Changes of Adult Mitral Valves after Failed CorMatrix ECM Repair

Background and objectives: CorMatrix acts as a tissue scaffold and is intended to promote the proliferation of small vessels and tissue remodeling to replicate normal tissue function. Methods: At Temple University Hospital, Philadelphia, PA, USA from 2013 to 2016, CorMatrix mate rial was utilized during mitral valve anterior leaflet aug mentation repair in 25 adult patients, and four patients required repeat interventions at 4–12 months (8.25 ± 4.35 months) after the initial repair. This study evaluated the pathological changes in four patients. Results: Histologi cal examination of the CorMatrix showed matrix degrada tion in all cases. At 4 months after repair, mixed acute and chronic inflammatory cells that included eosinophils were visible within the matrix, which was more severe around the suture material. Later, the extent of inflammation abated and became more chronic with macrophage domi nance. Some macrophages and multinucleated cells were visible deep in the matrix. The neovascularization was lim ited to the tissue–matrix boundary at early time points; the more mature vessels with dilated lumens extended deeper into the matrix as time increased, combined with some elongated fibroblast-like cells. In addition, marked acute and chronic inflammation with neutrophil and eo sinophil infiltrate was identified in the surrounding native tissue at 4 months, especially around the suture material. Marked granulomatous inflammation was identified in all cases, with prominent multinucleated giant cells present at later time points (50%). Immunohistochemical staining for CD68 and CD163 showed prominent M2 macrophages in the CorMatrix and surrounding tissue. Conclusions: Our results demonstrated time-dependent changes in failed CorMatrix repaired valves after mitral valve repair, with macrophages and neovascularization in the matrix 12 months after the initial repair.