AbstractOBJECTIVESUsing a large national database, we sought to describe outcome trends in mitral valve surgery between 2000 and 2019.METHODSThe study cohort was split into mitral valve repair (MVr) or replacement, including all patients regardless of concomitant procedures. Patients were grouped by four-year admission periods into groups (A to E). The primary outcome was in hospital mortality and secondary outcomes were return to theatre, postoperative stroke and postoperative length of stay. We investigated trends over time in patient demographics, comorbidities, intraoperative characteristics and postoperative outcomes. We used a multivariable binary logistic regression model to assess the relationship between mortality and time. Cohorts were further stratified by sex and aetiology.RESULTSOf the 63 000 patients in the study cohort, 31 644 had an MVr and 31 356 had a replacement. Significant demographic shifts were observed. Aetiology has shifted towards degenerative disease; endocarditis rates in MVr dropped initially but are now rising (period A = 6%, period C = 4%, period E = 6%;P< 0.001). The burden of comorbidities has increased over time. In the latest time period, women had lower repair rates (49% vs 67%,P< 0.001) and higher mortality rates when undergoing repair (3% vs 2%,P= 0.001) than men. Unadjusted postoperative mortality dropped in MVr (5% vs 2%,P< 0.001) and replacement (9% vs 7%,P= 0.015). Secondary outcomes have improved. Time period was an independent predictor for reduced mortality in both repair (odds ratio: 0.41, 95% confidence interval: 0.28–0.61,P< 0.001) and replacement (odds ratio: 0.50, 95% confidence interval: 0.41–0.61,P< 0.001).CONCLUSIONSIn-hospital mortality has dropped significantly over time for mitral valve surgery in the UK. MVr has become the more common procedure. Sex-based discrepancies in repair rates and mortality require further investigation. Endocarditis rates in MVS are rising.