Mitral valve disease remains an important cause of cardiovascular morbidity worldwide and continues to represent a substantial indication for surgical intervention. Rheumatic heart disease (RHD) remains a major cause of valvular heart disease, particularly in low- and middle-income countries, despite substantial reductions in disease burden in many high-income regions [1]. Global estimates demonstrate that RHD continues to affect millions of individuals, with South Asia carrying a particularly high burden [1]. In India, rheumatic valvular disease remains an important contributor to cardiovascular morbidity and constitutes a significant indication for mitral valve surgery.

Mitral valve disease may present with progressive stenosis, regurgitation, or mixed lesions, resulting in left atrial enlargement, atrial fibrillation, pulmonary hypertension, heart failure, and impaired functional capacity. Contemporary guidelines emphasize timely intervention in patients with severe symptomatic valve disease and in selected asymptomatic patients at risk of irreversible ventricular or pulmonary vascular consequences [2]. Although mitral valve repair is preferred when a durable repair is technically feasible, valve replacement remains necessary in patients with extensive rheumatic leaflet pathology, severe calcification, advanced subvalvular disease, failed previous repair, or anatomy unsuitable for durable reconstruction [2].

When mitral valve replacement is required, selection between mechanical and bioprosthetic prostheses represents an important clinical decision. Mechanical valves offer excellent long-term structural durability and a low risk of structural valve degeneration but require lifelong anticoagulation with vitamin K antagonists to reduce prosthetic thrombosis and thromboembolic complications [2,3]. Lifelong anticoagulation also introduces the potential for bleeding complications and requires regular monitoring of the international normalized ratio (INR). These considerations may be particularly important in settings where access to consistent anticoagulation monitoring and long-term follow-up is variable.

Bioprosthetic valves generally avoid the need for lifelong anticoagulation attributable solely to the prosthesis in patients without another indication for anticoagulation. However, their principal limitation is structural valve deterioration, which becomes increasingly relevant with longer follow-up and is more pronounced in younger patients [2,3]. Prosthesis selection therefore involves balancing valve durability against the risks and practical consequences of lifelong anticoagulation. Current guidelines recommend individualized selection based on age, life expectancy, bleeding and thromboembolic risk, anticipated prosthetic durability, potential need for future intervention, feasibility of anticoagulation monitoring, and patient preferences [2,3].

Comparative evidence demonstrates distinct long-term outcome profiles for mechanical and bioprosthetic valves. Mechanical valve replacement has generally been associated with lower rates of structural deterioration and repeat valve intervention, whereas bioprosthetic replacement may reduce the long-term burden of anticoagulation-related bleeding [3,4]. A systematic review and meta-analysis comparing mechanical and biological prostheses for mitral valve replacement demonstrated that prosthesis selection requires consideration of competing risks, including survival, thromboembolism, bleeding, and reoperation rather than reliance on a single outcome measure [4]. Large observational studies have similarly shown that outcomes vary according to age and other patient characteristics, supporting individualized prosthesis selection [3].

The issue is particularly relevant in India, where rheumatic mitral valve disease remains clinically important and socioeconomic circumstances, healthcare accessibility, infrastructure, adherence, and availability of regular INR monitoring may influence long-term outcomes [1]. Although international guidelines and comparative studies provide substantial evidence regarding prosthesis selection, differences in disease etiology, patient characteristics, anticoagulation practices, and follow-up patterns may limit direct extrapolation to Indian tertiary-care populations.

Furthermore, much of the available comparative evidence has originated from retrospective cohorts, registries, administrative databases, or long-term observational studies [3,4]. Prospective institutional data evaluating perioperative and early postoperative outcomes following mechanical versus bioprosthetic mitral valve replacement remain comparatively limited, particularly in Indian tertiary-care settings. Prospective assessment may therefore provide clinically relevant information regarding immediate surgical outcomes, postoperative complications, early functional recovery, and short-term valve-related events.

The present study was undertaken to prospectively compare the clinical outcomes of mechanical versus bioprosthetic mitral valve replacement among patients undergoing surgery at a tertiary-care hospital in India. The study aimed to evaluate perioperative and early postoperative outcomes between the two prosthesis groups and to assess clinically relevant differences in postoperative complications and early echocardiographic outcomes. The findings may provide additional context for prosthesis selection, individualized patient counselling, and perioperative management of patients undergoing mitral valve replacement.

Study Design: This was a prospective comparative observational study designed to compare perioperative and early postoperative clinical outcomes among patients undergoing mechanical versus bioprosthetic mitral valve replacement. Study Setting: The study was conducted in the Department of Cardiothoracic and Vascular Surgery at a tertiary-care hospital in India providing specialized cardiac surgical services. The department manages patients with rheumatic, degenerative, and other clinically significant mitral valve disorders requiring surgical intervention. Study Duration: The study was conducted over a period of two year, from July 2024 to June 2026. Study Population: The study population comprised adult patients with clinically significant mitral valve disease for whom mitral valve replacement was indicated and who underwent surgery during the study period. Patients were categorized according to the type of prosthetic valve implanted into two groups: Group I, mechanical mitral valve replacement, and Group II, bioprosthetic mitral valve replacement. Prosthesis Selection: The choice of prosthesis was made by the treating cardiac surgical team after consideration of patient age, clinical characteristics, anticipated prosthetic durability, anticoagulation-related considerations, and patient preference. Inclusion Criteria: Patients were eligible for inclusion if they were aged ≥18 years, had clinically significant mitral valve disease requiring mitral valve replacement, underwent mitral valve replacement during the study period, received either a mechanical or bioprosthetic mitral prosthesis, and provided written informed consent for participation and follow-up. Exclusion Criteria: Patients aged <18 years, those undergoing concomitant major cardiac surgical procedures likely to substantially influence postoperative outcomes, patients requiring emergency surgery for acute infective endocarditis or other immediately life-threatening conditions, those with incomplete baseline or postoperative clinical records, and patients unwilling or unable to provide informed consent or participate in follow-up were excluded. Sample Size: A formal a priori sample-size calculation was not performed because this was a prospective single-center observational study conducted over a predefined one-year recruitment period. All eligible patients undergoing mitral valve replacement during the study period were considered for inclusion and were enrolled consecutively. A total of 80 patients were included, comprising 40 patients in the mechanical-valve group and 40 patients in the bioprosthetic-valve group. Sampling Technique: Consecutive sampling was used. All patients undergoing mitral valve replacement during the study period who fulfilled the predefined eligibility criteria were assessed for inclusion and enrolled consecutively after obtaining informed consent. Data Collection Tools and Procedure: Data were collected prospectively using a structured data-collection proforma. Baseline demographic and clinical characteristics included age, sex, presenting symptoms, relevant comorbidities, indication for surgery, etiology of mitral valve disease, and relevant preoperative investigations. Preoperative echocardiographic parameters, including left ventricular ejection fraction and pulmonary artery pressure, were recorded. Operative data included prosthesis type, operative procedure, cardiopulmonary bypass duration, and aortic cross-clamp time. Patients were monitored throughout the postoperative period, and clinically relevant outcomes were documented, including duration of mechanical ventilation, ICU stay, total hospital stay, postoperative bleeding, blood transfusion, arrhythmias, thromboembolic events, acute kidney injury, infection, re-exploration, and mortality. Early postoperative echocardiographic findings were assessed during the index hospital admission before discharge. All collected information was entered into a structured database and reviewed for completeness and consistency before statistical analysis. Study Variables: The exposure variable was the type of mitral prosthesis, categorized as mechanical or bioprosthetic. Outcomes included perioperative, postoperative, and early echocardiographic parameters, including cardiopulmonary bypass and aortic cross-clamp duration, mechanical ventilation duration, ICU and hospital length of stay, postoperative complications, and postoperative echocardiographic parameters. Baseline characteristics, including age, sex, comorbidities, mitral valve etiology, and preoperative cardiac function, were considered potential covariates when evaluating differences between the two groups. Statistical Analysis: Statistical analysis was performed using IBM SPSS Statistics version 25.0. (IBM Corp., Armonk, NY, USA). Continuous variables were assessed for normality and expressed as mean ± standard deviation (SD) for approximately normally distributed data or as median with interquartile range (IQR) for non-normally distributed data. Categorical variables were presented as frequencies and percentages. For comparison between the two groups, normally distributed continuous variables were analyzed using the independent-samples t test, whereas non-normally distributed continuous variables were analyzed using the Mann-Whitney U test. Categorical variables were compared using the Pearson chi-square test or Fisher's exact test, as appropriate, particularly when expected cell frequencies were small. All statistical tests were two-sided, and a p-value <0.05 was considered statistically significant. Given the relatively small sample size, statistical findings were interpreted cautiously, particularly for uncommon postoperative events. Ethical Considerations: The study was conducted in accordance with the ethical principles of the Declaration of Helsinki and applicable institutional requirements. Ethical approval was obtained from the Institutional Ethics Committee (IEC) of the participating institution before commencement of the study. Written informed consent was obtained from all participants before enrolment. Patient confidentiality was maintained throughout the study, and personal identifiers were excluded from the analytical dataset and study reporting. Participation was voluntary, and participants were informed that refusal to participate or withdrawal from the study would not affect their clinical care.

A total of 80 patients undergoing mitral valve replacement were included in the study, with 40 patients receiving mechanical prostheses and 40 receiving bioprosthetic valves. Baseline demographic and clinical characteristics are presented in Table 1. Patients receiving mechanical valves were younger than those receiving bioprosthetic valves. The two groups were otherwise comparable with respect to sex distribution, rheumatic etiology, preoperative left ventricular ejection fraction (LVEF), and pulmonary artery pressure.

Table 1. Baseline demographic and clinical characteristics of the study population

SD, standard deviation; LVEF, left ventricular ejection fraction.

Operative and immediate postoperative outcomes

Operative and immediate postoperative outcomes are summarized in Table 2. Cardiopulmonary bypass time, aortic cross-clamp time, and duration of mechanical ventilation were comparable between the two groups. Patients receiving mechanical valves had a shorter ICU stay than those receiving bioprosthetic valves. Total hospital stay was comparable between groups.

Table 2. Intraoperative and immediate postoperative outcomes

ICU, intensive care unit; SD, standard deviation.

Postoperative complications

Postoperative complications are presented in Table 3. No statistically significant difference was observed between the groups for any individual postoperative complication. Atrial fibrillation was the most frequently observed complication in both groups. Postoperative bleeding, acute kidney injury, infection, thromboembolic events, re-exploration for bleeding, and in-hospital mortality were relatively uncommon.

Table 3. Postoperative complications

Early echocardiographic outcomes

Early postoperative echocardiographic findings are shown in Table 4. Postoperative LVEF was comparable between the mechanical- and bioprosthetic-valve groups. The mean change in LVEF from baseline was greater in the bioprosthetic group.

Table 4. Early postoperative echocardiographic outcomes

LVEF, left ventricular ejection fraction; SD, standard deviation.

The present prospective comparative study evaluated early postoperative outcomes following mechanical versus bioprosthetic mitral valve replacement. The principal findings were that patients receiving mechanical prostheses were younger, while most perioperative and early postoperative outcomes were comparable between the two groups. The mechanical-valve group had a shorter ICU stay, whereas cardiopulmonary bypass time, aortic cross-clamp time, mechanical ventilation duration, total hospital stays, postoperative complications, and early postoperative left ventricular ejection fraction (LVEF) did not demonstrate significant between-group differences. These findings suggest that prosthesis type was not associated with a consistent difference in early postoperative recovery or ventricular function. The significant difference in age between the two groups is consistent with established clinical practice regarding prosthesis selection. Mechanical valves provide greater structural durability but require lifelong anticoagulation, whereas bioprosthetic valves have a finite risk of structural valve deterioration but generally avoid lifelong anticoagulation attributable solely to the prosthesis. Current American and European guidelines therefore emphasize individualized selection based on age, life expectancy, bleeding and thromboembolic risk, anticipated prosthetic durability, feasibility of anticoagulation monitoring, and patient preferences [2,3]. Accordingly, the younger age observed among mechanical-valve recipients should be interpreted primarily as a reflection of clinical decision-making and patient selection rather than as an outcome attributable to prosthesis type. Rheumatic mitral valve disease constituted the predominant underlying etiology in both groups. This finding is relevant to the Indian setting, where rheumatic heart disease remains an important cause of valvular disease and continues to contribute substantially to the need for mitral valve surgery in South Asia [1]. The similar proportion of rheumatic disease between the two prosthesis groups indicates that the underlying etiology was broadly balanced and is unlikely to explain major differences in the observed early postoperative outcomes. Operative characteristics were comparable between the two groups. Cardiopulmonary bypass and aortic cross-clamp durations did not differ significantly, suggesting that the type of prosthesis did not materially influence the duration of the surgical procedure in this cohort. These parameters are more likely to be determined by valve pathology, surgical complexity, operative technique, and institutional practice than by the prosthesis selected. Similarly, the absence of a difference in postoperative mechanical ventilation supports the overall similarity of immediate postoperative recovery. The shorter ICU stay observed in the mechanical-valve group was the principal difference in early postoperative recovery. However, this finding should be interpreted cautiously. ICU duration is influenced by multiple perioperative factors, including hemodynamic stability, bleeding, arrhythmias, respiratory recovery, renal function, and institutional discharge practices. Furthermore, mechanical ventilation and total hospital stay were comparable between the groups. Therefore, the shorter ICU stay should be regarded as an observed association rather than evidence of a direct beneficial effect of mechanical prostheses. The non-randomized allocation of prosthesis type and the baseline age difference between groups may also have contributed to this finding. Postoperative complications were uncommon and did not differ significantly between prosthesis groups. In particular, postoperative bleeding, atrial fibrillation, acute kidney injury, infection, re-exploration for bleeding, thromboembolic events, and in-hospital mortality showed no statistically significant between-group differences. These findings are relevant because the principal theoretical clinical trade-off between mechanical and bioprosthetic valves involves long-term anticoagulation and prosthetic durability rather than necessarily differences in immediate postoperative complications. Mechanical prostheses require lifelong anticoagulation, which is associated with cumulative bleeding risk, whereas bioprosthetic valves avoid lifelong anticoagulation attributable solely to the prosthesis in patients without another indication [4,5]. The absence of a significant difference in early postoperative bleeding in the present study therefore should not be interpreted as demonstrating equivalence in long-term bleeding risk. Similarly, thromboembolic events were infrequent, limiting meaningful comparison between the groups. Larger comparative studies have demonstrated differences in long-term thromboembolic outcomes between mechanical and bioprosthetic valves, although these outcomes are strongly influenced by anticoagulation management and patient characteristics [4]. Thus, the low event rate in the present study supports cautious interpretation and does not permit conclusions regarding the relative long-term thromboembolic safety of the two prosthesis types. Atrial fibrillation was among the more frequently observed postoperative complications in both groups, but no significant difference was identified. Postoperative atrial fibrillation is multifactorial and may be influenced by age, atrial enlargement, rheumatic disease, surgical stress, inflammation, and perioperative physiological changes. Its similar occurrence between the two prosthesis groups is therefore clinically plausible and suggests that prosthesis type alone is unlikely to be a major determinant of early postoperative atrial fibrillation. Early postoperative ventricular function was also comparable. Postoperative LVEF did not differ significantly between mechanical- and bioprosthetic-valve recipients, indicating broadly preserved ventricular systolic function following mitral valve replacement irrespective of prosthesis type. The observed postoperative ventricular response is consistent with the primary purpose of mitral valve replacement, namely correction of abnormal loading conditions and restoration of effective forward flow. Because the present study evaluated LVEF only during the early postoperative period, these findings should not be extrapolated to long-term ventricular remodeling or prosthetic performance. The present findings should be interpreted alongside larger comparative studies that have primarily evaluated long-term outcomes. A systematic review and meta-analysis involving 35,903 patients reported lower long-term mortality and fewer mitral reoperations with mechanical prostheses but higher risks of major bleeding and stroke or systemic embolism compared with bioprosthetic valves [4]. Similarly, an updated meta-analysis of patients younger than 70 years reported lower operative and long-term mortality and reoperation rates with mechanical prostheses, together with a higher risk of bleeding [5]. These studies address outcomes over substantially longer periods than the present investigation. Therefore, the absence of significant differences in most early postoperative outcomes in the present cohort does not contradict the established differences in longer-term prosthesis-related outcomes. Age remains an important factor when balancing prosthetic durability against the burden of lifelong anticoagulation. Long-term studies have demonstrated greater structural deterioration of bioprosthetic valves in younger patients, whereas the relative advantage of mechanical-valve durability becomes less pronounced with increasing age because of competing mortality and the lower likelihood of clinically important structural deterioration during the patient's remaining lifespan [6,7]. Pooled individual-patient analyses of bioprosthetic mitral valves have similarly demonstrated an inverse relationship between patient age and structural valve deterioration [8]. These observations reinforce the principle that prosthesis selection should be individualized rather than based on a universal preference for either mechanical or bioprosthetic valves. The clinical relevance of prosthesis selection may be particularly important in settings where long-term anticoagulation monitoring is difficult. Mechanical valves may be appropriate for selected younger patients with a long-expected lifespan and reliable access to anticoagulation monitoring, whereas bioprosthetic valves may be considered when avoidance of lifelong anticoagulation is an important priority. Contemporary recommendations therefore favor shared decision-making based on individual clinical circumstances rather than age alone [2,3]. In the Indian setting, accessibility of INR monitoring, treatment adherence, socioeconomic circumstances, occupational considerations, and the feasibility of long-term follow-up may additionally influence the choice of prosthesis. The present study has several strengths, including its prospective comparative design, consecutive recruitment, predefined eligibility criteria, standardized assessment of perioperative and postoperative outcomes, and inclusion of early echocardiographic assessment. Nevertheless, several limitations should be acknowledged. The single-center observational design limits generalizability, and prosthesis allocation was not randomized; therefore, residual confounding, particularly related to age and other factors influencing prosthesis selection, cannot be excluded. The relatively small number of patients and low incidence of major adverse events also limit the ability to detect differences in uncommon outcomes such as thromboembolism, re-exploration, and mortality. Importantly, the present study was designed to assess early postoperative outcomes and therefore cannot establish differences in long-term structural valve deterioration, prosthetic durability, cumulative bleeding, thromboembolism, reoperation, or survival. Longer-term prospective follow-up and larger multicenter studies will be required to address these outcomes.

This prospective comparative study demonstrated comparable early outcomes following mechanical and bioprosthetic mitral valve replacement. Apart from a shorter ICU stay in the mechanical-valve group, no significant differences were observed in operative parameters, duration of mechanical ventilation, total hospital stay, postoperative complications, or early left ventricular ejection fraction. The younger age of patients receiving mechanical valves reflects clinical prosthesis selection based on factors such as anticipated durability and anticoagulation considerations rather than an outcome effect attributable to valve type. Overall, both prosthesis types provided satisfactory early postoperative results. However, the limited number of patients, non-randomized design, and short follow-up restrict conclusions regarding uncommon complications and long-term outcomes. Valve selection should therefore remain individualized, balancing patient age, durability, anticoagulation requirements, bleeding and thromboembolic risks, and patient preference. Larger studies with long-term follow-up are needed to establish differences in prosthetic durability, reoperation, major bleeding, thromboembolism, and survival.

DECLARATIONS

Funding: No external funding was received for this study.

Conflict of Interest: The authors declare no conflict of interest.

Ethical Approval: The study protocol was submitted to and approved by the Institutional Ethics Committee (IEC) of the participating institution before commencement of the study.

Consent: Written informed consent was obtained from all participants before enrolment in accordance with institutional ethical requirements and the principles of the Declaration of Helsinki.

Acknowledgment: The authors acknowledge the support of the Department of Cardiothoracic and Vascular Surgery and the clinical and nursing staff involved in the care and follow-up of patients.

1. Watkins DA, Johnson CO, Colquhoun SM, Karthikeyan G, Beaton A, Bukhman G, et al. Global, regional, and national burden of rheumatic heart disease, 1990–2015. New england journal of medicine. 2017 Aug 24;377(8):713-22. 2. Vahanian A, Beyersdorf F, Praz F, Milojevic M, Baldus S, Bauersachs J, Capodanno D, Conradi L, De Bonis M, De Paulis R, Delgado V. 2021 ESC/EACTS guidelines for the management of valvular heart disease. Eur heart J. 2022 Feb 12;43(7):561-632. 3. Otto CM, Nishimura RA, Bonow RO, Carabello BA, Erwin III JP, Gentile F, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021 Feb 2;143(5):e72-227. 4. Yu J, Qiao E, Wang W. Mechanical or biologic prostheses for mitral valve replacement: a systematic review and meta‐analysis. Clinical Cardiology. 2022 Jul;45(7):701-16. 5. Ahmed A, Awad AK, Varghese KS, Sehgal VS, Hisham K, George J, Pandey R, Vega E, Polizzi M, Mathew DM. Bioprosthetic versus mechanical valves for mitral valve replacement in patients< 70 years: an updated pairwise meta-analysis. General Thoracic and Cardiovascular Surgery. 2024 Feb;72(2):95-103. 6. Goldstone AB, Chiu P, Baiocchi M, Lingala B, Patrick WL, Fischbein MP, Woo YJ. Mechanical or biologic prostheses for aortic-valve and mitral-valve replacement. New England Journal of Medicine. 2017 Nov 9;377(19):1847-57. 7. Hammermeister K, Sethi GK, Henderson WG, Grover FL, Oprian C, Rahimtoola SH. Outcomes 15 years after valve replacement with a mechanical versus a bioprosthetic valve: final report of the Veterans Affairs randomized trial. Journal of the American College of Cardiology. 2000 Oct;36(4):1152-8. 8. Koulouroudias M, Di Mauro M, Chiariello G, Meani P, Lorusso R. Long-term outcomes of bioprosthetic valves in the mitral position: a pooled meta-analysis of reconstructed time-to-event individual patient data. The American Journal of Cardiology. 2024 Jun 15;221:64-73.