Systematic evaluation of the flexible and rigid annuloplasty ring after mitral valve repair for mitral regurgitation

Objectives: Mitral annulus reconstruction is now a common surgical procedure for the treatment of mitral regurgitation. However, there are still controversies in the selection of materials for annuloplasty in the clinical controlled studies available. The purpose of the present systematic review of the literature is to address whether a flexible ring is superior to a rigid ring in terms of improvement in clinical and echocardiographic outcomes.

Methods: A systematic literature search was undertaken of all clinical control trials comparing the outcomes of mitral annuloplasty surgery with the flexible and rigid ring in MEDLINE, EMBASE, and the Cochrane Library.

Results: Overall, 12 published trials were identified as being eligible for overview and were included in the meta-analysis study between 1966 and 2010: four prospective randomized and eight case-control studies. Combined hazard ratios suggested that the flexible annuloplasty ring had no favorable impact on survival: the mean (95% confidence interval (CI)) was 1.24 (0.24-2.24). From the mortality data at maximum follow-up ranging 35-61 months, there was no significant difference on mortality, reoperation, and significant recurrent mitral regurgitation between the two rings. Also, we were not able to find an improvement by flexible rings on shortening fraction, left ventricular end-diastolic volume, end-systolic volume, and end-diastolic and end-systolic diameter. There was a significantly higher ejection fraction in arms for flexible rings relative to rigid rings with pooled standardized mean deviation (SMD) 0.29, 95% CI: 0.06-0.52, p=0.015. Finally, compared to the rigid annuloplasty ring, patients implanted with flexible ones presented significantly a far better effect preserving the mitral valve area: SMD 0.54, 95% CI: 0.13-0.95, p=0.01, and less constrictive for blood flow across the mitral valve, with the pooled SMD of peak velocity (flexible vs rigid: -0.63, 95% CI: -1.12 to -0.13, p=0.013).

Conclusions: Except for the improvement in ejection fraction and preserving the mitral valve area effects in the flexible cases, it remains comparable with regard to overall survival, mortality, reoperation, regurgitant recurrence, and left ventricular performance between the flexible and rigid ring.