Clinical and Pathological Features of Degenerative Mitral Valve Disease: Billowing Mitral Leaflet Versus Fibroelastic Deficiency

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Purpose: Degenerative mitral valve disease is distinguished with billowing mitral leaflet (BML) or fibroelastic deficiency (FED). The purpose of this study is to evaluate the clinical characteristics and the pathohistological differences between BML and FED.Methods: A total of 73 patients who diagnosed as degenerative mitral valve disease pathologically after mitral valve surgery for severe mitral regurgitation were enrolled. On the basis of echocardiographic features and gross appearances, they were classified as BML (9 cases) and FED (64 cases).Results: In the BML group, multiple segments of the leaflet showed billowing with elongated chordae. Therefore excessive valve tissue needed to be removed by multiple resection and suture. The FED patients had focal myxomatous changes with ruptured chordae, a single resection and suture was frequently employed. In pathological examination, the valve thickness of the BML was nearly twice as thick as the FED, and the mucopolysaccharide accumulation of the Spongiosa in the BML was over 50%, while 30% in the FED.Conclusion: BML presents the characteristic valve thickening due to its abnormal production of mucopolysaccharide. Since excessive tissue was voluminous in the BML, high-grade plasty techniques, such as combination of multiple resection and chordal reconstruction were required.