Bioprosthetic vs mechanical mitral valve replacement for infective endocarditis in patients aged 50 to 69 years

Abstract Background The optimal choice of the valve prosthesis in mitral valve replacement (MVR) for infective endocarditis (IE) is controversial and challenging, particularly for younger patients. Hypothesis The postoperative outcomes of mechanical and biological MVR in IE patients aged 50 to 69 years are different. Methods All IE patients aged 50 to 69 years with primary MVR in Hubei province hospitals from 2002 to 2018 were retrospectively reviewed. The median duration of follow‐up was 8.7 years (IQR, 6.8‐10.9 years). Propensity score matching (1:3 ratio) was used to yield 492 patients with comparable baseline features between bioprostheses and mechanical prosthetic valve groups. Outcomes were postoperative mid‐ to long‐ term survival, mitral valve reoperation, prosthetic valve endocarditis (PVE), stroke, and major bleeding events. Results Fifteen‐year survival after MVR was 80.6% in the mechanical valve group and 69.3% in the bioprostheses group (HR 0.545, P = .040). The cumulative incidence of mitral valve reoperation was 8.8% with mechanical valves and 21.4% with bioprostheses (HR 0.260, P = .002). The cumulative incidence of PVE was 5.6% with mechanical valves and 7.2% with bioprostheses (HR 0.629, P = .435). The cumulative incidence of stroke was 12.9% with mechanical valves and 10.5% with bioprostheses (HR 1.217, P = .647). The cumulative incidence of major bleeding was 12.0% with mechanical valves and 6.75% with bioprostheses (HR 1.579, P = .268). Conclusions Mechanical valve prostheses were associated with better survival, lower rates of reoperation compared with bioprostheses within 15 years after MVR in IE patients aged 50 to 69. These findings suggest mechanical valve prostheses may be a more reasonable alternative to bioprostheses in this patient group.

these ages, recent consensus guidelines recommend an individualized approach to prosthesis selection based on patient factors and preferences.
To clarify the ideal choice of prosthesis in native mitral valve IE, we designed this study and compared long-term survival, incidence of reoperation, prosthetic valve endocarditis (PVE), stroke, and major bleeding events between bioprostheses and mechanical MVR in IE patients aged 50 to 69 years.

| PATIENTS AND METHODS
A retrospective cohort study comparing long-term outcomes after Of these patients, 754 (9.13%) had a principal diagnosis of IE identified by ICD-9-CM diagnosis codes (421.0, 421.1, and 421.9) during the index hospitalization. Fifty six patients who had received previous valve surgery were excluded. Patients were more likely to undergo mechanical prosthetic MVR (562 patients; 80.5%) than bioprostheses prosthetic MVR (136 patients; 19.5%) in our study. To minimize potential selection bias, we calculated a propensity score from selected variables and matched each patient in the bioprostheses prosthetic group with each patient in the mechanical prosthetic group.
Finally, 123 patients of the bioprostheses prosthetic group and 369 patients of the mechanical prosthetic group were identified and were eligible for analysis ( Figure 1).
Preoperative clinical characteristics, operation variables, and postoperative inhospital complications were acquired according to the medical records. Follow-up data were acquired through clinic reexamination and telephone interview. The follow-up was 98.2% complete; median follow-up time was 8.7 years (interquartile range [IQR], 6.8-10.9 years) with maximum follow-up of 16.5 years. Median follow-up time was 8.8 years (IQR, 6.8-11.0 years) in the mechanical prosthesis group compared with 8.5 years (IQR, 6.6-10.8 years) in the bioprosthesis group.
Adverse events were classified according to the standardized definitions from the Society of Thoracic Surgeons/American Association for Thoracic Surgery "Guidelines for Reporting Morbidity and Cardiac Valvular Operations." 9 The primary study end-points included overall mortality. The secondary study end-points were reoperation, PVE, stroke, and major bleeding events. Stroke was defined as any cerebrovascular accident documented during the index hospitalization as well as any subsequent hospital admission in which the principal diagnosis was hemorrhagic or ischemic stroke. Reoperation was defined as any subsequent MVR. Major bleeding event was defined as requiring hospitalization or blood transfusion. PVE was diagnosed by ultrasonic cardiogram.
Baseline patient characteristics are represented as means with SD for continuous variables and proportions for categorical variables. To compare baseline differences in comorbidity between patients receiving mechanical prosthetic and bioprostheses valves, the t test was performed for continuous variables, the Pearson χ 2 test was performed for categorical variables, and standardized differences were calculated for all variables.
Confounding due to differences in baseline characteristics was addressed using propensity score matching. 10 To calculate the propensity score, a hierarchical logistic regression model was fitted with F I G U R E 1 Study population flowchart T A B L E 1 Patient baseline characteristics in the overall cohort and propensity score matching groups according to type of mitral valve replacement 3 | RESULTS

| Patients characteristics
The baseline characteristics and operative characteristics of the overall cohort are presented in Table 1

| Survival
Among patients matched by propensity score, mid-to long-term survival was significantly higher among patients treated with a mechanical prosthetic than those treated with a biological prosthesis

| Major bleeding events
The rates of major bleeding events during the follow-up period were not significantly different in patients with a mechanical and biological prosthesis (HR, 1.579 [95% CI, 0.704-3.539], P = .268; Figure 3D).
The cumulative incidence of major bleeding events at 5, 10, and 15 years were 5.67%, 10.82%, and 12.01% in the mechanical prosthesis group, and 3.11%, 6.75%, and 6.75% in the bioprosthesis group, The dilemma about prosthesis selection will arise immediately once when patients decide to replace the destructed mitral valve. 15 The choice of valve type is determined by balancing the risk of anticoagulationrelated and thromboembolic complications with mechanical valves vs the risk of structural failure and reoperation with bioprosthetic valves. Since there is no agreement on the optimal valve prosthetic choice in the setting of infective endocarditis, in most cases we need to refer to the consensus guidelines for the management of valvular heart disease. [16][17][18] In  The main limitations of this study are its retrospective observational nature, which may impact generalizability. We use the propensity score analysis method to minimize the impact of confounders related to treatment selection and heterogeneity in baseline factors; however, the fact that some patients had contraindications for a long-

| CONCLUSIONS
This propensity score-matched study compared 15-year outcomes between mechanical and bioprosthetic MVR in infective endocarditis patients aged 50 to 69 years. We found that there was no significant difference in incidence of prosthetic valve endocarditis, major bleeding, or stroke between the two types of prostheses, but mechanical valve prostheses were associated with the better survival and lower rate of reoperation. These findings suggest mechanical valve prostheses may be a more reasonable alternative to bioprostheses in this patient group.

ACKNOWLEDGEMENT
We thank Prof Ping Yin for his guidance in statistical approach.