**A. Appendix**

#### **A.1 Echocardiographic evaluation**

In this study, echocardiographic evaluation was performed in MR subjects before and after surgery using an echo machine (SONOS 7500; Philips) [23]. LV and left atrial volume (LAV) were determined using the modified Simpson's method. LAV was measured at the end-systole just before the mitral valve opening, and LV and LA volume indices, which were divided by the body surface area, were obtained. Right ventricular systolic pressure (RVSP) was obtained by adding the systolic tricuspid pressure gradient calculated by the modified Bernoulli equation and right atrial pressure [24]. Transmitral flow was assessed using pulsed Doppler by placing the sample volume at the level of leaflet tips, and early filling (E) and atrial contraction filling (A) velocities were measured. Tissue Doppler velocity of the mitral annulus in early diastole (e<sup>0</sup> ) was also measured. MR severity was quantified as averaged effective regurgitant orifice area (ERO) obtained by the Doppler volumetric method [25].

#### **A.2 Statistical analysis**

As for statistical analysis, comparisons among groups were performed by Student's t test or one way analyses of variance, followed by Bonferroni test when necessary. The relationships between WI indices and β were evaluated by correlation and regression analysis. Univariate regression analyses were performed for the data relating pulmonary hypertension before surgery to the variables measured before surgery and for the data relating EF after surgery to the variables measured before surgery. Then, the variables that were correlated with RVSP before surgery

and EF after surgery (p ≤ 0.1) were entered into stepwise multivariate regression models. To obtain the threshold value of predictor variable separating a clinical diagnosis that EF after surgery≥50% from one that EF after surgery <50%, the ROC curves were created, and the optimal combinations of sensitivity and specificity were chosen. A p value <0.05 was set for statistical significance.
