European Journal of Cardiovascular Medicine

Background: Monoleaflet tilting-disc mechanical valves were widely used before the contemporary bileaflet era. Their structural durability is well established, but contemporary cohorts documenting prostheses remaining in situ for four decades are uncommon. Objective: To describe the long-term observed longevity of monoleaflet mechanical prostheses in the mitral and aortic positions, with particular emphasis on patients reaching at least 40 years after implantation. Methods: We retrospectively reviewed 673 patient records. Operative descriptions were used to identify valve position and prosthesis type. Follow-up was recalculated from the recorded operation date to the last recorded follow-up. Entries with non-calendar operation fields, impossible chronology or invalid date-derived intervals were excluded from date-based analyses. Continuous follow-up was summarized using mean, median, interquartile range (IQR) and maximum duration. Formal Kaplan-Meier survival was prespecified but deferred because the database contains 'Yes', 'No' and 'NA' vital-status entries without consistently documented death dates or an adjudicated censoring definition. Results: Valid date-derived follow-up was available for 468 mitral and 315 aortic valve-position observations. Mean follow-up was 13.75 years for mitral and 13.60 years for aortic prostheses; median follow-up was 12.86 and 12.79 years, respectively. Maximum verified follow-up was 43.45 years in both positions. Five patients had verified follow-up of at least 40 years, all recorded alive at the latest follow-up. The longest observation was 43.45 years in a patient with a Björk-Shiley mitral and Lillehei-Kaster aortic prosthesis. Conclusion: This cohort documents exceptional observed longevity of historical monoleaflet mechanical valves, with multiple patients followed beyond 40 years. Definitive actuarial survival estimates require adjudication of death dates and censoring status