Sedransk Kyra L, Grande-Allen K Jane, Vesely Ivan
Hathaway Brown School, Shaker Heights, Ohio, USA.
J Heart Valve Dis. 2002 Sep;11(5):644-50.
Rupture of chordae tendineae is the main cause of mitral valve insufficiency, and often requires corrective surgery. The precise mechanisms of chordal rupture, however, are unknown.
Failure mechanics were measured in porcine mitral valve chordae (37 anterior marginal, 40 anterior basal, 35 posterior marginal, and 38 posterior basal). Full-length chordae were weighed, measured, and stretched to failure in an Instron tensile testing machine. The ruptured ends were characterized under a dissecting microscope.
Marginal chordae had 68% thinner cross-sectional areas and failed at 68% less load and 28% less strain than basal chordae. Chordae from the posterior leaflet were 35% thinner and failed at 43% less load and 22% less strain than anterior leaflet chordae. Failure strength was lowest for posterior marginal chordae. Chordae most frequently tore just below the leaflet insertion, in what was often their narrowest section.
Overall, the marginal chordae and posterior leaflet chordae were thinner and required less strain and load to fail than basal chordae and anterior leaflet chordae, respectively. These results support previous reports of decreased extensibility in marginal chordae. The high incidence of ruptures in the posterior marginal chordae of diseased mitral valves may be due to an inherent weakness in these chordae.
腱索断裂是二尖瓣关闭不全的主要原因，通常需要进行矫正手术。然而，腱索断裂的确切机制尚不清楚。
对猪二尖瓣腱索（37根前外侧、40根前内侧、35根后外侧和38根后内侧）进行破坏力学测定。对全长腱索进行称重、测量，并在英斯特朗拉伸试验机上拉伸至断裂。在解剖显微镜下对断裂端进行表征。
外侧腱索的横截面积比内侧腱索薄68%，断裂时承受的载荷比内侧腱索少68%，应变比内侧腱索少28%。后叶腱索比前叶腱索薄35%，断裂时承受的载荷比前叶腱索少43%，应变比前叶腱索少22%。后外侧腱索的破坏强度最低。腱索最常于瓣叶附着点下方撕裂，此处往往是腱索最狭窄的部位。
总体而言，外侧腱索和后叶腱索比内侧腱索和前叶腱索更薄，断裂时分别需要更小的应变和载荷。这些结果支持了先前关于外侧腱索伸展性降低的报道。病变二尖瓣后外侧腱索断裂的高发生率可能是由于这些腱索存在内在薄弱环节。
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