Mitral Valve Annuloplasty Rings: Review of Literature and Comparison of Functional Outcome and Ventricular Dimensions

In the past decades, more than 40 mitral valve annuloplasty rings of various shapes and consistency were marketed for mitral regurgitation (MR), although the effect of ring type on clinical outcome remains unclear. Our objective was to review the literature and apply a simplification method to make rings of different shapes and rigidity more comparable. We studied relevant literature from MEDLINE and EMBASE databases related to clinical studies as well as animal and finite element models. Annuloplasty rings were clustered into 3 groups as follows: rigid (R), flexible (F), and semirigid (S). Only clinical articles regarding degenerative (DEG) or ischemic/dilated cardiomyopathy (ICM) MR were included and stratified into these groups. A total of 37 rings were clustered into R, F, and S subgroups. Clinical studies with a mean follow-up of less than 1 year and a reported mean etiology of valve incompetence of less than 60% were excluded from the analysis. Forty-one publications were included. Preimplant and postimplant end points were New York Heart Association class, left ventricular ejection fraction (LVEF), left ventricular end-systolic dimension (LVESD), and left ventricular end-diastolic dimension (LVEDD). Statistical analysis included paired-samples t test and analysis of variance with post hoc Bonferroni correction. P < 0.05 indicated statistical difference. Mean ± SD follow-up was 38.6 ± 27 and 29.7 ± 13.2 months for DEG and ICM, respectively. In DEG, LVEF remained unchanged, and LVESD decreased in all subgroups. In our analysis, LVEDD decreased only in F and R, and S did not change; however, the 4 individual studies showed a significant decline. In ICM, New York Heart Association class improved in all subgroups, and LVEF increased. Moreover, LVESD and LVEDD decreased only in F and S; R was underpowered (1 study). No statistical difference among R, F, and S in either ICM or DEG could be detected for all end points. Overall, owing to underpowered data sets derived from limited available publications, major statistical differences in clinical outcome between ring types could not be substantiated. Essential end points such as recurrent MR and survival were incomparable. In conclusion, ring morphology and consistency do not seem to play a major clinical role in mitral valve repair based on the present literature. Hence, until demonstrated otherwise, surgeons may choose their ring upon their judgment, tailored to specific patient needs.