• annuloplasty
• mitral valve
• ring size prediction

Mathematical Approach for Ring Size Prediction in Degenerative Mitral Valve Repair
Abstract

Background

The implantation of a prosthetic ring during Mitral Valve Repair (MVRe) is a pillar in valvular surgery. The sizing is usually assessed during the surgery, based on well established, eye-ball techniques.
Preoperative prediction of the correct ring-size, through a mathematical approach, could be a useful tool to help the surgeon’s choice.

Objective

The aim of the study is to evaluate a new formula to perform a preoperative prediction of the prosthetic ring/band size to be implanted in surgical MVRe. We therefore propose a mathematical approach based on transthoracic echocardiography measurements developed to achieve a coaptation length (CL) of 8 millimeters in order to obtain an optimal repair.

Methods

Patients affected by Degenerative Mitral Valve Regurgitation (DMR), who underwent surgical MVRe from July 2021 to July 2023, were retrospectively evaluated. Pre-operative Coaptation Length (CL0) and antero-posterior (AP) diameter have been measured in PLAX view during telesystole, while Anterior Mitral Leaflet (AML) length, Posterior Mitral Leaflet length (PML) in mid-diastole. All measurements were performed three times by one operator (EM) and then blindly validated by an expert echocardiographer (GSF). Mean values were calculated and then plotted into the ideated formula. A CL of 8 mm was selected, based on literature showing a long-lasting effective MVRe necessitates of a post-operative CL between 5 and 10 mm. The following formula was developed: .
The prosthetic ring/band corresponding to the pAP was selected in blind respect to the ring/band that was actually implanted.
Using the pAP, the surgeon can then, using the charts provided by each manufacturer, deduct and confirm the most appropriate ring size for the annuloplasty.
A concordance study was developed using the two tailed t-test for paired samples and the Pearson correlation coefficient test (PCC).
To compare categorical and continuous variables, which could have influenced the concordance, we usedChi-squared test and two-tailed t-test for unpaired samples, respectively.

Results

Fifty-four patients were included in the study; 6 implanted a SimuPlus Band (SPB), 17 CG Future Band (CGFB) and 31 Simulus Ring (SR) (Medtronic, Minneapolis, MN USA). 32 (57,1%) patients were males and 24 (42,9%) females, with a mean age of 64 ±13.
Mean Left Ventricular Ejection Fraction (LVEF) was 61% ±6.
Their data were collected retrospectively and analyzed. Pearson test showed a good correlation between the predicted and surgically measured and implanted ring sizes (PCC r: 0,589; p <0,001). No correlation was found between categorical and continuous variables and the concordance of the prediction, except for the ring type. In details, SR and CGFB demonstrated different correlations (r=0,745, P<0,001; r=0,659; p=0,004; respectively). SPB showed no correlation.

Discussion and Conclusion

The proposed method showed good results in terms of ring size prediction, using a non-invasive, wide available and cost-effective method. In details, its efficiency was superior in case of semi-rigid, complete ring; acceptable in case of semirigid, incomplete band; and unsuccessful in case of a soft, incomplete band.
The ring-size prediction has been already described by other studies. Most of them reported the use of TC scan, 3D-printed models, invasive examinations, software processing or complex multi-parametric formulas. All the previously reported methods appear to be expensive and require a lot of funds, a higher level of complexity and have lower reproducibility. The proposed mathematical formula represents an easier, repeatable, cost-effective and readily available method for ring size prediction, and could be helpful in the surgeon’s choice.
Further studies are needed to investigate the effectiveness in a larger population and the potential utilization in transcatheter annuloplasty solutions.