Levine R A, Triulzi M O, Harrigan P, Weyman A E
Circulation. 1987 Apr;75(4):756-67. doi: 10.1161/01.cir.75.4.756.
The geometric or anatomic diagnosis of mitral valve prolapse, as opposed to the pathologic diagnosis of myxomatous valve disease, is based on the relationship of the mitral leaflets to the surrounding anulus. Current echocardiographic criteria for this diagnosis include leaflet displacement above the annular hinge points in any two-dimensional view; implicit in this equivalent use of intersecting views is the assumption that the mitral anulus is a euclidean plane. Prolapse by these criteria is found in a surprisingly large proportion of the general population. In most of these individuals, however, prolapse is present in the apical four-chamber view and absent in roughly orthogonal long-axis views of the left ventricle. This frequently observed discrepancy between leaflet-annular relationships in intersecting views suggests an underlying geometric property of the mitral apparatus that would produce the appearance of prolapse in one view without actual leaflet distortion. To address this possibility, a model of the mitral valve and anulus was constructed. When the model anulus was given a nonplanar, saddle-shaped configuration, the clinical observations were reproduced: the leaflets appeared to lie above the low points of the anulus in one plane, and below its high points in a perpendicular plane. Therefore, the appearance of mitral valve prolapse can occur without actual leaflet displacement above the most superior points of the mitral anulus if the anulus is nonplanar. To determine whether this pattern is reflected in the human mitral anulus, two-dimensional echocardiographic views of the mitral apparatus were obtained by rotation about the cardiac apex in 20 patients without evident annular or rheumatic valvular disease. In all cases the mitral anulus, as reconstructed from these views, had a nonplanar systolic configuration, with high points located anteriorly and posteriorly. This is consistent with the findings of other groups in animals, and would favor the appearance of prolapse in the four-chamber view and its absence in long-axis views that are oriented anteroposteriorly. This model can therefore explain the frequently observed discrepancy between leaflet-annular relationships in roughly orthogonal views. It challenges the assumption that the mitral anulus is planar as well as the diagnosis of prolapse in many otherwise normal individuals based on that assumption.
二尖瓣脱垂的几何或解剖学诊断，与黏液瘤样瓣膜病的病理学诊断不同，是基于二尖瓣叶与周围瓣环的关系。目前用于该诊断的超声心动图标准包括在任何二维视图中叶瓣高于瓣环铰链点；这种交叉视图的等效使用中隐含的假设是二尖瓣瓣环是一个欧几里得平面。根据这些标准，在普通人群中发现脱垂的比例惊人地高。然而，在这些个体中的大多数，脱垂出现在心尖四腔视图中，而在左心室大致正交的长轴视图中不存在。在交叉视图中叶瓣与瓣环关系中经常观察到的这种差异表明二尖瓣装置存在一种潜在的几何特性，即在一个视图中会产生脱垂的外观而没有实际的叶瓣变形。为了探讨这种可能性，构建了一个二尖瓣和瓣环的模型。当模型瓣环具有非平面的鞍形结构时，再现了临床观察结果：叶瓣在一个平面上似乎位于瓣环低点上方，而在垂直平面上位于其高点下方。因此，如果瓣环是非平面的，二尖瓣脱垂的外观可以在没有实际叶瓣高于二尖瓣瓣环最上点的情况下出现。为了确定这种模式是否反映在人类二尖瓣瓣环中，对20名没有明显瓣环或风湿性瓣膜病的患者围绕心尖进行旋转，获得了二尖瓣装置的二维超声心动图视图。在所有情况下，从这些视图重建的二尖瓣瓣环具有非平面的收缩期结构，高点位于前方和后方。这与其他研究组在动物中的发现一致，并且有利于在四腔视图中出现脱垂而在前后方向的长轴视图中不存在脱垂。因此，该模型可以解释在大致正交视图中叶瓣与瓣环关系中经常观察到的差异。它挑战了二尖瓣瓣环是平面的假设以及基于该假设对许多其他方面正常个体的脱垂诊断。
