Evidence of vicious cycle in mitral regurgitation with prolapse : Secondary tethering due to primary prolapse demonstrated by 3-dimensional echocardiography exacerbates regurgitation

背景：在二尖瓣脱垂（MVP）患者中，非脱垂的瓣叶通常会在心尖形成帐篷状。我们假设1），继发性左心室（LV）扩张由于原发性二尖瓣返流（MR）导致这瓣叶帐篷/拴系和2），继发性拴系进一步加剧接合不良，并有助于MR severity.Methods和结果：三维（3D）经食管超声心动图（TEE）进行了25例后叶（PML）脱垂与完整的前叶（AML）和20个对照。从3D缩放数据集，获得了收缩中期MV的11个等距前后切割平面。在每个平面上，测量非脱垂瓣叶的帐篷面积和脱垂瓣叶的脱垂面积。每个区域的脱垂/隆起体积作为层间距离和脱垂/隆起面积的乘积获得。然后获得AML帐篷体积和整个瓣叶脱垂/帐篷体积。MR的严重程度由从彩色3DTEE数据集中提取的缩脉面积（VCA）来量化。与对照组相比，PML脱垂患者的AML帐篷体积显着更大（1.2±0.5 vs. 0.6±0.2 ml/m^2，p<0.001）。多变量回归分析确定了AML帐篷体积的独立贡献来自于收缩中期LV体积的增加（r=0.79，p<0.001）沿着瓣环扩张。多变量回归分析确定了全瓣叶隆起体积（r=0.63，p<0.001）以及脱垂体积（r=0.60，p <0.001）对二尖瓣返流严重程度（VCA）的独立贡献。AML帐篷体积沿着减少，与术后左室体积相关（n=7，p<0.01）。结论：这些结果表明，由于左室扩张和瓣环扩张，原发性MVP伴二尖瓣返流导致继发性二尖瓣瓣叶栓系，进一步加剧瓣膜泄漏，构成恶性循环，提示早期手术修复的病理生理学依据。

Background : In patients with mitral valve prolapse(MVP), non-prolapsed leaflets are often apically tented. We hypothesized 1) that secondary left ventricular(LV) dilatation due to primary mitral regurgitation(MR) causes this leaflet tenting/tethering and 2) that secondary tethering further exacerbates malcoaptation and contributes to MR severity.Methods and Results : Three-dimensional(3D) transesophageal echocardiography(TEE) was performed in 25 patients with posterior leaflet(PML) prolapse with an intact anterior leaflet(AML) and 20 controls. From 3D zoom datasets, 11 equidistant antero-posterior cut planes of the MV at mid-systole were obtained. In each plane, tenting area of non-prolapsed leaflet and prolapse area of prolapsed leaflet were measured. Prolapse/tenting volume of each region was obtained as the product of inter-slice distance and the prolapse/tenting area. AML tenting volume and whole leaflet prolapse/tenting volume were then obtained. The severity of MR was quantified by vena contracta area(VCA) extracted from color 3DTEE datasets. AML tenting volume was significantly larger in patients with PML prolapse compared with that in controls(1.2±0.5 vs. 0.6±0.2 ml/m^2, p<0.001). Multivariate regression analysis identified independent contributions to AML tenting volume from an increase in mid-systolic LV volume(r=0.79, p<0.001) along with annular dilatation. Multivariate regression analysis identified independent contributions to MR severity(VCA) from both whole leaflet tenting volume(r=0.63, p<0.001) as well as prolapse volume(r=0.60, p<0.001). AML tenting volume decreased along with LV volume post-repair(n=7, p<0.01).Conclusion : These results suggest that primary MVP with MR causes secondary mitral leaflet tethering due to LV dilatation and annular dilatation, which further exacerbates valve leakage, constituting a vicious cycle that would suggest a pathophysiologic rationale for early surgical repair.