Background-Mitral valve (MV) repair is preferred over replacement in clinical guidelines and is an important determinant of the indication for surgery in degenerative mitral regurgitation (MR). Yet, the level of evidence supporting current recommendations is low, and recent data cast doubts on its validity in the current era. Accordingly, the aim of the present study was to analyze very long-term outcome after MV repair and replacement for degenerative MR with a flail leaflet. Methods-MIDA is a multicenter registry enrolling patients with degenerative MR with a flail leaflet in 6 tertiary European and US centers. We analyzed the outcome after MV repair (n=1,709) and replacement (n= 213), overall, by propensity score matching and by inverse probability-of-treatment weighting. Results-At baseline, patients undergoing MV repair were younger, had more comorbidities and were more likely to present with a posterior leaflet prolapse than those undergoing MV replacement. After propensity score matching as well as after inverse probability-of-treatment weighting, the 2 treatments groups were balanced and absolute standardized differences were usually below 10%, indicating adequate match. Operative mortality (defined as a death occurring within 30 days from surgery or during the same hospitalization) was lower after MV repair than after replacement, both in the entire (1.3 vs 4.7%; p<0.001) and in propensity-matched population (0.2% vs 4.4%; p<0.001). During a mean follow-up of 9.2 years, 552 deaths were observed, of which 207 were of cardiovascular origin. Twenty-year survival was better after MV repair than after MV replacement, both in the entire (46% vs 23%, p<0.001) and in matched population (41% vs 24%, p<0.001). Similar superiority of MV repair were obtained in patients' subsets based on age, sex or any stratification criteria (all p<0.001). MV repair was also associated with reduced incidence of reoperations and valve-related complications.Conclusions-Among patients with degenerative MR with a flail leaflet, referred to mitral surgery, MV repair was associated with lower operative mortality, better long-term survival and fewer valve-related complications compared to MV replacement.

These results demonstrate that the NeoChord procedure is safe, effective and reproducible. Clinical and echocardiographic efficacy is maintained up to 1 year with significant differences among the anatomical groups. Specific anatomical selection criteria are necessary to achieve stable results.

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