Mathematical modeling for predicting the optimal size of ring annuloplasty in the repair of degenerative mitral valves

Background: During mitral valve repair (MVRe), the sizing of the prosthetic ring/band often depends more on the surgeon's experience than objective methodology. The study aims to validate a mathematical approach based on transthoracic echocardiography to predict the optimal ring size in a surgical cohort. Methods: Patients who underwent MVRe between July 2021 and July 2023 were retrospectively evaluated. Pre-operative echocardiography data were collected [including pre-operative coaptation length (CL0), anteroposterior (AP) diameter, anterior mitral leaflet (AML) length, posterior mitral leaflet (PML) length]. A dedicated formula was developed to predict the postoperative AP (pAP) diameter, ensuring a CL of 8 mm, according to the literature. Based on the calculated pAP, the optimal ring size was selected using the manufacturer's ring charts. A linear regression study tested the consistency between the predicted and implanted sizes. Results: Fifty-four patients were included; six implanted a Flexible Band, 17 a Semirigid Band, and 31 a Semirigid Ring. In linear regression, there was an acceptable correlation between predicted/implanted sizes (r=0.589; P<0.001). Overall, the only factor influencing concordance was ring type. When analyzing the single ring groups, we found that correlation was impacted by ring type with an optimal correlation for Semirigid Rings (r=0.745, P<0.001), good for Semirigid Bands (r=0.659, P=0.004), and poor for Flexible Bands. Conclusions: The proposed method is reliable in predicting the optimal ring size, with a CL >8 mm; however, the test's ability is influenced by the type of ring. Further studies are needed to validate the formula in a larger population and investigate its use in transcatheter annuloplasty.