Mitral valve enlargement in chronic aortic regurgitation as a compensatory mechanism to prevent functional mitral regurgitation in the dilated left ventricle.

OBJECTIVES: The aim of this study was to test the hypothesis that mitral valve (MV) enlargement occurring in chronic aortic regurgitation (AR) prevents functional mitral regurgitation (FMR). BACKGROUND: Chronic AR causes left ventricular (LV) dilation, creating the potential for FMR. However, FMR is typically absent during compensated AR despite substantial LV enlargement. Increased mitral leaflet area has been identified in AR, but it is unknown whether increased MV size can represent a compensatory mechanism capable of preventing FMR. METHODS: Database review of 816 patients with at least moderate AR evaluated the prevalence of FMR. A total of 90 patients were enrolled prospectively for 3-dimensional echocardiography (30 AR, 30 FMR, and 30 controls) to assess MV geometry including total leaflet area. RESULTS: FMR was present in 5.6% of AR patients by database review. Prospectively, only 1 AR patient had more than mild FMR despite increased LV end-diastolic volume (82 ± 22, 86 ± 23, and 51 ± 12 cm(3)/m(2), respectively, for AR, FMR vs. control patients; p < 0.01) and similar sphericity index, annular area, and tethering distances compared with FMR. Total MV area was largest in AR (31.3% greater than normal), increasing significantly more than in FMR. The ratio of valve size to closure area was maintained in AR, whereas decreases in this ratio and LV ejection fraction independently predicted FMR. CONCLUSIONS: FMR prevalence is low in chronic AR. MV leaflet area is significantly increased compared with control and FMR patients, preserving a normal relationship to the area needed for closure in the dilated LV. Understanding the mechanisms underlying this adaptation could lead to new therapeutic interventions to prevent FMR.

Diagnostic value of vena contracta area in the quantification of mitral regurgitation severity by color Doppler 3D echocardiography.

BACKGROUND: Accurate quantification of mitral regurgitation (MR) is important for patient treatment and prognosis. Three-dimensional echocardiography allows for the direct measure of the regurgitant orifice area (ROA) by 3D-guided planimetry of the vena contracta area (VCA). We aimed to (1) establish 3D VCA ranges and cutoff values for MR grading, using the American Society of Echocardiography-recommended 2D integrative method as a reference, and (2) compare 2D and 3D methods of ROA to establish a common calibration for MR grading. METHODS AND RESULTS: Eighty-three patients with at least mild MR underwent 2D and 3D echocardiography. Direct planimetry of VCA was performed by 3D echocardiography. Two-dimensional quantification of MR included 2D ROA by proximal isovelocity surface area (PISA) method, vena contracta width, and ratio of jet area to left atrial area. There were significant differences in 3D VCA among patients with different MR grades. As assessed by receiver operating characteristic analysis, 3D VCA at a best cutoff value of 0.41 cm(2) yielded 97% of sensitivity and 82% of specificity to differentiate moderate from severe MR. There was significant difference between 2D ROA and 3D VCA in patients with functional MR, resulting in an underestimation of ROA by 2D PISA method by 27% as compared with 3D VCA. Multivariable regression analysis showed functional MR as etiology was the only predictor of underestimation of ROA by the 2D PISA method. CONCLUSIONS: Three-dimensional VCA provides a single, directly visualized, and reliable measurement of ROA, which classifies MR severity comparable to current clinical practice using the American Society of Echocardiography-recommended 2D integrative method. The 3D VCA method improves accuracy of MR grading compared with the 2D PISA method by eliminating geometric and flow assumptions, allowing for uniform clinical grading cutoffs and ranges that apply regardless of etiology and orifice shape.