Impact of Mitral Valve Repair Case Volume on Postoperative Mortality　- A Nationwide Korean Cohort Study.

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.

The association between hospital case volume and in-hospital and one-year mortality after hip fracture surgery.

AIMS: Hospital case volume is shown to be associated with postoperative outcomes in various types of surgery. However, conflicting results of volume-outcome relationship have been reported in hip fracture surgery. This retrospective cohort study aimed to evaluate the association between hospital case volume and postoperative outcomes in patients who had hip fracture surgery. We hypothesized that higher case volume would be associated with lower risk of in-hospital and one-year mortality after hip fracture surgery. METHODS: Data for all patients who underwent surgery for hip fracture from January 2008 to December 2016 were extracted from the Korean National Healthcare Insurance Service database. According to mean annual case volume of surgery for hip fracture, hospitals were classified into very low (< 30 cases/year), low (30 to 50 cases/year), intermediate (50 to 100 cases/year), high (100 to 150 cases/year), or very high (> 150 cases/year) groups. The association between hospital case volume and in-hospital mortality or one-year mortality was assessed using the logistic regression model to adjust for age, sex, type of fracture, type of anaesthesia, transfusion, comorbidities, and year of surgery. RESULTS: Between January 2008 and December 2016, 269,535 patients underwent hip fracture surgery in 1,567 hospitals in Korea. Compared to hospitals with very high volume, in-hospital mortality rates were significantly higher in those with high volume (odds ratio (OR) 1.10, 95% confidence interval ((CI) 1.02 to 1.17, p = 0.011), low volume (OR 1.22, 95% CI 1.14 to 1.32, p < 0.001), and very low volume (OR 1.25, 95% CI 1.16 to 1.34, p < 0.001). Similarly, hospitals with lower case volume showed higher one-year mortality rates compared to hospitals with very high case volume (low volume group, OR 1.15, 95% CI 1.11 to 1.19, p < 0.001; very low volume group, OR 1.10, 95% CI 1.07 to 1.14, p < 0.001). CONCLUSION: Higher hospital case volume of hip fracture surgery was associated with lower in-hospital mortality and one-year mortality in a dose-response fashion. Cite this article: Bone Joint J 2020;102-B(10):1384-1391.