Mortality and cause of death in patients undergoing mitral valve surgery for mitral regurgitation: a nationwide cohort study

Abstract Background For patients undergoing mitral valve surgery for mitral regurgitation (MR), data on mortality and causes of death remain sparse. Such data could provide a more complete picture of what patients can expect in the long term following surgery. Purpose To compare the incidence of mortality and the distribution of cardiovascular vs. non-cardiovascular causes of death in patients undergoing mitral valve surgery for MR relative to controls from the general population. Methods Using Danish nationwide registries, we identified patients ≥18 years of age discharged following first-time non-transcatheter surgery for MR (1996-2021) and four times as many matched controls from the general population. We excluded patients with prior or concomitant infective endocarditis. Controls were age-, sex- and calendar year-matched. Mortality was assessed using the reverse Kaplan-Meier estimator with a maximum follow-up of 10 years. Causes of death were classified as either cardiovascular (CV) or non-cardiovascular (non-CV) using the International Classification of Diseases 10th edition and stratified into two follow-up time bands after index 1) 0-1 year of follow-up and 2) 1-10 years of follow-up. Results We identified 6,855 patients who underwent surgery for MR, and 27,420 matched controls (median age 66 years, 66% male). The median follow-up times were 7.7 years in patients and 8.5 years in controls, with a mortality rate of 35% (n=1,837) in patients and 25% (n=5,294) in controls, Figure 1a. Overall, CV deaths constituted 51% of deaths in patients compared to 26% in controls (p0.001). When comparing the two follow-up time bands, the proportion of CV deaths was 65.4% in the first year and declined to 48.2% in the subsequent nine years, Figure 1b. Among matched controls, the proportion of CV deaths remained stable throughout the follow-up period, Figure 1b. Conclusion Mortality in patients undergoing mitral valve surgery for mitral regurgitation was significantly higher as compared to matched controls. Cardiovascular death was the most common cause of death among patients in the first postoperative year but declined in the following years. For matched controls, the proportion of cardiovascular causes was stable at around one fourth of all causes of death.