Impact of mitral valve repair case volume on postoperative mortality: A nationwide Korean cohort study

Abstract

Background: Although mitral valve repair is recommended over replacement due to better outcomes, repair rates vary significantly among centers. This study examined the effect of institutional mitral valve repair volume on postoperative mortality. Methods and Results: All cases of adult mitral valve repair performed in Korea between 2009 and 2016 were analyzed. The association between case volume and 1-year mortality was analyzed after categorizing centers according to the number of mitral valve repairs performed as low-, medium-, or high-volume centers (<20, 20–40, and >40 cases/year, respectively). The effect of case volume on cumulative all-cause mortality was also assessed. In all, 6,041 mitral valve repairs were performed in 86 centers. The 1-year mortality in low-, medium-, and high-volume centers was 10.1%, 8.7%, and 4.7%, respectively. Low- and medium-volume centers had increased risk of 1-year mortality compared with high-volume centers, with odds ratios of 2.80 (95% confidence interval [CI] 2.15–3.64; P<0.001) and 2.66 (95% CI 1.94–3.64; P<0.001), respectively. The risk of cumulative all-cause mortality was also worse in low- and medium-volume centers, with hazard ratios of 1.96 (95% CI 1.68–2.29; P<0.001) and 1.77 (95% CI 1.47–2.12; P<0.001), respectively. Conclusions: Lower institutional case volume was associated with higher mortality after mitral valve repair. A minimum volume standard may be required for hospitals performing mitral valve repair to guarantee adequate outcome.