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

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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.