Long-term outcomes after mitral valve surgery in a 25-year nationwide cohort with age-dependent prosthesis effects

Background Long-term nationwide data comparing mitral valve repair versus replacement and age-dependent outcomes of mechanical versus bioprosthetic valves remain limited. Objectives To evaluate 25-year national trends and long-term outcomes of mitral valve surgery and to determine age-modified associations between mechanical and bioprosthetic prostheses. Methods Using Taiwan’s National Health Insurance Research Database (1997–2022), we identified 19,844 patients undergoing mitral valve repair or replacement. The primary outcome was all-cause mortality. Secondary outcomes included heart failure (HF) hospitalization, stroke or systemic embolization (SSE), major bleeding, and reoperation. Kaplan–Meier analyses and multivariable Cox models adjusted for age, sex, and comorbidities were performed. Age interactions were evaluated using restricted cubic splines. Results Among 19,844 patients, 8,877 underwent repair and 10,967 replacement (3,833 mechanical; 5,408 bioprosthetic). Replacement patients were older (62.9±14.2 vs 53.4±13.3 years, p<0.001) and had higher comorbidity burden. Over a median follow-up of 70.9 months, 7,513 deaths occurred. Compared with repair, replacement was associated with higher all-cause mortality (adjusted HR 1.87, 95% CI 1.70–2.07; p<0.001), HF hospitalization (HR 1.75, 95% CI 1.54–1.98; p<0.001), and stroke/SSE (HR 2.35, 95% CI 2.08–2.65; p<0.001). Among replacement strategies, mechanical valves were associated with increased major bleeding (HR 2.67, 95% CI 2.37–3.00; p<0.001) and hemorrhagic stroke (HR 2.82, 95% CI 2.23–3.57; p<0.001) compared with bioprosthetic valves, but lower reoperation risk (HR 0.62, 95% CI 0.49–0.79; p<0.001). Spline-adjusted modeling demonstrated significant age interaction for mortality (P for interaction<0.001). Mechanical valves were associated with lower mortality in younger patients, with survival advantage most pronounced below 60–65 years, but this benefit attenuated with advancing age and was no longer observed in patients ≥70 years (HR 1.03 at age 70; 95% CI 0.90–1.17). In contrast, excess bleeding risk with mechanical valves persisted across all age strata. Conclusions In this nationwide 25-year cohort, mitral valve repair was associated with superior long-term outcomes compared with replacement. Mechanical valves provided an age-dependent survival advantage in younger patients but at the cost of substantially increased bleeding risk, with diminishing mortality benefit in older individuals. These findings support individualized, age-tailored prosthesis selection.Cubic spine curve