Determinants of Disproportionality in Functional Mitral Regurgitation　- Importance of Mitral Valve Morphology.

BACKGROUND: Disproportionate (d-) functional mitral regurgitation (FMR) is characterized by greater mitral regurgitation (MR) severity than expected from left ventricular (LV) dilatation. Morphological determinants of this imbalance remain unclear. METHODS AND RESULTS: Consecutive patients who underwent transcatheter edge-to-edge repair (TEER) for symptomatic FMR were divided into 2 groups: d-FMR and proportionate (p-) FMR (effective regurgitant orifice area [EROA]/LV end-diastolic volume [LVEDV] >0.20 or ≤0.20 mm2/mL, respectively). Of the 114 FMR patients included, those with d-FMR (n=66) were more likely to be female and had a significantly larger EROA than patients with p-FMR (n=48), despite a smaller LVEDV index and lower tenting height. Metrics of LV dyssynchrony and etiologies were similar between the 2 groups, but the d-FMR group had a higher proportion of pseudo-prolapse (28.8% vs. 8.3%; P=0.007), extreme mitral annular dilatation (>700 mm2/m2; 53.0% vs. 29.2%; P=0.011), and deep indentation (24.2% vs. 4.2%; P=0.004). Although these factors were prevalent in the population, no patient with MR due purely to any of these factors underwent TEER. After adjustment by age, sex, and LVEDV index, the number of factors present was associated with d-FMR (odds ratio 4.15; P<0.001). Similar results were obtained when using an EROA/LVEDV cut-off of 0.14 mm2/mL. CONCLUSIONS: Additional morphological factors were associated with greater MR severity beyond LV size and with residual MR after TEER, supporting a phenotype-based interpretation of FMR disproportionality.