European Journal of Cardiovascular Medicine

Mechanical heart valves remain the most durable valve substitutes and continue to have an important role in patients with long life expectancy when long-term vitamin K antagonist therapy is acceptable. Contemporary guidelines emphasize individualized prosthesis selection based on age, life expectancy, bleeding and thromboembolic risk, anticoagulation feasibility, and patient preference [1-3].

The tilting-disc monoleaflet era represented a major advance from earlier caged-ball prostheses. The Björk-Shiley, Lillehei-Kaster and Medtronic Hall valves were designed to improve central flow, effective orifice area and mechanical reliability. Historical series established low rates of structural mechanical failure, although thromboembolism, anticoagulation-related bleeding, endocarditis, pannus and prosthetic thrombosis remained clinically important late events [4-10].

Long-term Medtronic Hall experience is particularly informative. Butchart et al. reported 1,766 procedures with 12,688 patient-years of follow-up and concluded that the valve had excellent durability and very low thrombogenicity at 20 years [4]. Svennevig et al. subsequently reported 25-year outcomes in 816 consecutive aortic recipients, demonstrating no mechanical failures in the reported cohort [5]. Björk-Shiley studies similarly show durable function into the second and third postoperative decades [6-8]. Lillehei-Kaster series also reported absence or rarity of mechanical failure despite valve-related morbidity associated with anticoagulation and thromboembolism [9-11].

Because patients implanted in the 1970s and 1980s are now reaching four to five decades after surgery, documentation of surviving patients with original monoleaflet prostheses provides clinically relevant evidence of real-world prosthetic longevity. The objective of this study was therefore to characterize the long-term observed follow-up of monoleaflet valves in mitral and aortic positions and to describe the subgroup with at least 40 years of verified follow-up.

Study design

This was a retrospective observational cohort analysis of a historical mechanical-valve database. The manuscript is structured as an original research article in accordance with the European Journal of Cardiovascular Medicine format, with IMRaD organization and Vancouver-style numbered citations.

Study population and valve classification

The source spreadsheet contained 673 patient records. Valve position was identified from the operative description using explicit terms such as mitral valve replacement/MVR and aortic valve replacement/AVR. Prosthesis nomenclature was normalized where possible to Medtronic Hall, Björk-Shiley and Lillehei-Kaster. Because some historical entries contain abbreviations or spelling variants, uncertain records were retained as 'other/uncertain' rather than being force-classified. Patients with double-valve replacement could contribute one mitral and one aortic valve-position observation; consequently, valve-position totals are not independent patient totals and must not be added to derive cohort size.

Follow-up definition and data quality

Follow-up duration was recalculated as the interval from the recorded operation date to the last recorded follow-up date using 365.2425 days per year. The spreadsheet's existing 'Years of follow up' variable was not used as the primary duration measure because internal review identified inconsistent and biologically implausible values. For the strict date-derived analysis, the operation and last-follow-up fields were required to be true calendar dates, the operation year had to be 1970-2026, and the last follow-up could not precede surgery.

Outcomes

The primary descriptive outcome was observed prosthesis follow-up duration. Secondary descriptive outcomes included follow-up according to mitral versus aortic position, number of observations reaching 20, 30 and 40 years, and characteristics of patients with at least 40 years of verified follow-up. Patient survival, prosthesis survival and structural durability were treated as distinct concepts in accordance with valve-outcome reporting principles [12].

Statistical analysis and Kaplan-Meier plan

Continuous variables are summarized by mean, median, IQR and range; categorical variables are presented as counts and percentages. A Kaplan-Meier analysis of all-cause survival was planned according to standard valve-reporting recommendations, including numbers at risk and confidence intervals [12]. However, the available vital-status field contains 336 'Yes', 50 'No', 286 'NA' and one blank entry. The database does not consistently provide a verified date of death for records marked 'No', and the meaning of 'NA' cannot be assumed to represent either alive censoring or death. Therefore, a formal Kaplan-Meier survival curve and 10-, 20-, 30- and 40-year actuarial survival percentages are intentionally not reported in this revision, because doing so would introduce outcome misclassification. A descriptive observed-follow-up curve is shown instead.

Cohort composition

Table 1. Cohort characteristics and status of key database fields.

Distribution of monoleaflet prostheses

Table 2. Distribution of normalized prosthesis categories. Counts by position may overlap in double-valve recipients. The 'other/uncertain' group includes historical descriptions that could not be reliably normalized from the operative text alone.

Observed longevity according to valve position

Table 3. Observed date-derived longevity according to valve position. A double-valve patient may appear in both position columns.

 Four-decade survivors

Table 4. Patients with at least 40 years of verified follow-up. Five unique patients met the threshold. The patient with double-valve replacement contributes to both the mitral and aortic ≥40-year position counts in Table 3.

 Milestone follow-up burden

 Table 5. Unique-patient follow-up milestones among records with valid date-derived follow-up. These are descriptive follow-up proportions, not survival probabilities.

The principal finding of this study is the documentation of multiple patients with monoleaflet mechanical prostheses followed for more than 40 years. The maximum verified duration was 43.45 years in both mitral and aortic positions, and five unique patients had at least 40 years of verified follow-up. This observation is important because it extends the clinical time horizon beyond most conventional long-term prosthetic-valve series.

The present findings are biologically and clinically consistent with the known durability of mechanical valves. In the 20-year Medtronic Hall experience reported by Butchart et al., valve thrombosis rates were very low and outcomes were predominantly influenced by patient-related risk factors rather than structural prosthetic failure [4]. In the 25-year aortic Medtronic Hall cohort, Svennevig et al. reported no mechanical failures, further supporting the capacity of this design to function for decades [5].

Long-term Björk-Shiley data provide a complementary historical perspective. Alvarez et al. described 831 Björk-Shiley recipients with substantial cumulative follow-up [6]. Ahn et al. reported 83.1% overall survival at 20 years in a Björk-Shiley Monostrut cohort, with 92.5% freedom from reoperation at 20 years [7]. In the Edinburgh randomized trial, Oxenham et al. found that survival with the original prosthesis intact at 20 years was substantially better with the Björk-Shiley mechanical valve than with porcine bioprostheses, although bleeding was more frequent in the mechanical-valve group [8]. These observations reinforce the distinction between mechanical durability and anticoagulation-related morbidity.

Lillehei-Kaster experience similarly demonstrated strong mechanical durability. Olesen et al. reported long-term aortic follow-up with only one valve thrombosis and no prosthesis fracture [9], while mitral and combined mitral-aortic cohorts showed that thromboembolism rather than mechanical fracture was the dominant valve-related concern [10,11]. Stewart et al. also reported no mechanical valve failures in a long-term Lillehei-Kaster aortic series [13]. The 43.45-year double-valve survivor in the present database, with a Lillehei-Kaster aortic prosthesis and Björk-Shiley mitral prosthesis, is therefore consistent with the mechanical reliability described in these historical reports.

Contemporary evidence continues to support mechanical prostheses when durability is prioritized. The Veterans Affairs randomized trial showed virtually absent primary mechanical valve failure at 15 years compared with age-dependent bioprosthetic failure [14]. Goldstone et al. demonstrated that the long-term balance between mechanical and biological prostheses depends on age and valve position, with mechanical prostheses reducing reoperation at the cost of greater bleeding risk in selected groups [15]. Current European and American guidelines accordingly emphasize individualized selection rather than a universal prosthesis choice [1-3].

An important interpretive point is that the approximately 13-year median follow-up in this database is not a measure of valve life expectancy. Median follow-up describes the distribution of observation time across the cohort. The existence of multiple verified observations beyond 40 years is the appropriate descriptive evidence for extreme longevity. Similarly, a patient being alive 40 years after implantation is not synonymous with 40-year freedom from all valve-related events. Prosthesis survival, patient survival, structural valve deterioration, reoperation and valve-related morbidity should be reported as separate endpoints [12].

The study also highlights a methodological issue relevant to historical databases. A Kaplan-Meier curve is only valid when event status and event/censoring time are defined consistently. The current spreadsheet contains a large 'NA' vital-status category and does not consistently pair 'No' status with a date of death. Treating NA as alive or treating the last clinic visit of a deceased patient as the death date would generate biased survival estimates. The correct next step is adjudication of the 50 'No' records and 286 'NA' records against hospital records, death certificates, family/physician follow-up or other reliable sources. Once this is completed, true 10-, 20-, 30- and 40-year Kaplan-Meier survival with 95% confidence intervals and numbers at risk can be added.

CLINICAL IMPLICATIONS

Historical monoleaflet prostheses should not be regarded as obsolete solely because of implantation age. In a patient with satisfactory leaflet motion, acceptable gradients, no significant regurgitation or paravalvular leak, no prosthetic infection, and stable anticoagulation, prosthesis age alone is not evidence of structural failure. However, lifelong surveillance remains necessary because thromboembolism, bleeding, thrombosis, pannus, endocarditis and paravalvular complications may occur even when the mechanical occluder remains structurally intact [2,4,5,12].

LIMITATIONS

The study is retrospective and relies on historical records with heterogeneous nomenclature. Baseline age, rhythm, ventricular function, valve pathology, anticoagulation quality and valve-related complications are not uniformly structured in the current spreadsheet. Some operation-date fields were stored as non-date values and were excluded from strict date-derived analysis. Prosthesis classification based on free-text operative descriptions may be imperfect. Double-valve recipients contribute to both position-specific analyses, so position counts are not independent patient cohorts. Most importantly, death dates and censoring status are not yet sufficiently adjudicated for formal actuarial survival. Accordingly, this manuscript makes a conservative claim of observed longevity beyond 40 years rather than an unsupported claim of a specific 40-year Kaplan-Meier survival percentage.

This historical cohort demonstrates exceptional observed longevity of monoleaflet mechanical heart valves. Five patients had verified follow-up of at least 40 years, and the maximum verified duration was 43.45 years, with four-decade observations present in both mitral and aortic positions. The findings complement established long-term Medtronic Hall, Björk-Shiley and Lillehei-Kaster literature and illustrate the capacity of tilting-disc mechanical prostheses to remain in situ for several decades. After adjudication of death dates and censoring status, a formal Kaplan-Meier analysis should be added to quantify actuarial 10-, 20-, 30- and 40-year patient survival.

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