[Background]
During mitral valve repair for degenerative mitral regurgitation (MR), optimal annuloplasty ring is associated with better clinical outcomes. The size of annuloplasty ring is generally determined by sizer in the cardioplegic arrested heart. Three-dimensional transesophageal echocardiography (3D-TEE), which can measure the mitral annulus under beating heart, can help to select the annuloplasty ring. We compared the measurements of MV between 3D-TEE and sizer and assessed whether the size of mitral annuloplasty ring can be predicted by 3D-TEE.
[Methods]
This study enrolled retrospectively 133 cases underwent MV repair for moderate to severe degenerative MR between January 2015 and December 2016 in our institution. By using an iE33 ultrasound system (Philips), the 3D zoom of MV was collected under general anaesthesia. The 3D image at mid-systole frame was selected for analysis, and we measured the commissure-commissure (CC) diameter and the anterior-posterior (AP) diameter of the middle anterior leaflet (A2). The size of annuloplasty ring its self was determined using by sizer, which measured the mitral annulus under cardioplegic cardiac arrest and direct vision. Correlation between the size of annuloplasty ring and predicted size by 3D-TEE was analyzed with multiple regression analysis. 
[Results]
Using 3D-TEE, the CC diameter was 30.6 ± 2.2 cm, the AP (A2) diameter was 20.6 ± 2.2 cm. The size of annuloplasty ring was 30.2 ± 2.1 cm. With the multiple regression analysis, (annuloplasty ring (cm)) = 4.77 + 0.77 × (CC diameter (cm)) + 0.09 × (AP (A2) diameter (cm)). The contribution rate (R2) was 0.76 (p<0.001) (Figure1). The standardized partial regression coefficient was 0.82 (p<0.001) for the CC diameter and 0.10 (p=0.04) for the AP (A2) diameter. 
[Conclusion]
There was a strong correlation between using sizer and using 3D-TEE for measuring the mitral annulus. In particular, CC diameter of MV is effective for determining the size of annuloplasty ring. In the future, we are going to evaluate whether the discrepancy between 3D-TEE and the size of annuloplasty ring affect long-term clinical outcomes.

Prediction of the size of annuloplasty ring for mitral valve repair using by three-dimensional transesophageal echocardiography