Impact of mitral valve repair case volume on postoperative mortality: a population-based observational study

Abstract

Introduction Although mitral valve repair is recommended over replacement when feasible due to its better outcomes, repair rates vary remarkably between cardiac surgery centers. The aim of this study is to examine the effect of institutional case volume on mortality after mitral valve repair. Methods We analyzed all cases of adult mitral valve repair performed in Korea between 2007 and 2016 using administrative data. The association between case volume and 1-year mortality after mitral valve repair was analyzed after categorizing centers depending on the number of mitral valve repairs performed; low- ( 20 and 40 cases/year, reference) volume centers. The effect of case volume on cumulative all-cause mortality was also assessed. Results A total of 6041 cases were performed in 86 centers. One-year mortality was 10.1% (175/1728), 8.7% (93/1067), and 4.7% (153/3246) in low-, medium-, and high-volume centers, respectively. Low- and medium-volume centers showed increased risk of 1-year mortality compared to high-volume centers (OR [95% CI]; 2.80 [2.15–3.64] and 2.66 [1.94–3.64], respectively.). The risk of cumulative all-cause mortality of up to 10 years was also worse in low- and medium-volume centers (HR [95% CI]; 1.96 [1.68–2.29] and 1.77 [1.47–2.12], respectively.). Discussion Lower case-volume was associated with higher risk of mortality after mitral valve repair. A minimum case volume may be required for hospitals performing mitral valve repair to guarantee adequate patient outcome.