Outcomes of Mechanical Mitral Valve Replacement with Preservation of Posterior Leaflet in Patients with Reduced Left Ventricular Function

1. Introduction

Mitral valve disease continues to represent a significant cardiovascular burden globally, with mechanical valve replacement remaining essential for younger patients requiring long-term durability [1,2]. Traditional surgical approaches involving complete excision of valvular and subvalvular components have undergone substantial evolution following recognition of the subvalvular apparatus's importance in maintaining ventricular geometry and contractile efficiency [3,4].

The preservation of anatomical continuity between the mitral apparatus and ventricular wall has emerged as an advanced technique that sustains structural and functional integrity essential for optimal cardiac mechanics [5,6]. This strategy shows particular relevance for patients with compromised ventricular function, who historically faced increased perioperative risk and suboptimal functional recovery [7,8].

Several investigations have documented favorable outcomes with subvalvular preservation approaches, even among patients with diminished cardiac performance [9,10]. The physiological benefits derive from maintained ventricular architecture and papillary muscle function, which become especially critical in patients with pre-existing ventricular dysfunction [11,12]. Despite encouraging preliminary results, comprehensive evaluation of this specific patient population remains limited, with reported early mortality varying considerably from 2.3% to 12.6% [13,14].

This investigation aims to systematically evaluate outcomes associated with mechanical mitral valve replacement incorporating posterior leaflet preservation in patients with reduced ventricular function, examining both immediate postoperative results and medium-term clinical progress. Our research provides valuable insights regarding the safety and efficacy of this surgical approach in this particularly challenging cohort.

2. Materials and Methods

2.1. Study Design and Population

This prospective, observational investigation was conducted at Hue Central Hospital from March 2015 through September 2016. To determine the appropriate sample size, we utilized the following formula for comparing two means:

n = 2(Zα/2 + Zβ)²σ²/d²

Where:

• n = required participants per group
• Zα/2 = 1.96 (significance level α = 0.05)
• Zβ = 0.842 (power = 80%)
• σ = standard deviation of ejection fraction improvement (7.5% from preliminary data)
• d = expected difference in ejection fraction improvement between groups (10%)

Based on statistical calculations, a minimum of 35 participants per group was required. To account for potential attrition during follow-up, we included at least 38 participants per cohort.

We evaluated all patients undergoing mechanical mitral valve replacement with posterior leaflet preservation for possible inclusion. Participants were categorized into either the study cohort (EF ≤50%) or comparison cohort (EF >50%) based on preoperative ventricular function assessment. The final study population comprised 87 participants meeting inclusion criteria, with 38 individuals in the reduced EF group and 49 in the preserved EF group..

2.2. Selection Criteria

Inclusion criteria encompassed adult patients (≥18 years) presenting with mitral valve pathology necessitating mechanical valve replacement. We implemented comprehensive exclusion parameters, including concurrent aortic valve procedures, coronary revascularization, previous cardiac operations, emergency interventions, congenital cardiac anomalies, and primary cardiomyopathies.

2.3. Surgical Technique

All interventions were performed through median sternotomy under cardiopulmonary bypass conditions. The posterior leaflet preservation technique involved careful excision of the anterior leaflet while meticulously preserving the posterior leaflet and its subvalvular components. The preserved posterior leaflet was subsequently secured to the mitral annulus using specialized U-shaped sutures. Two mechanical prostheses were employed: ATS and St. Jude valves, with diameters ranging from 25 to 31 mm, selected according to individual anatomical factors.

2.4. Data Collection and Follow-up

Preoperative assessment included detailed demographic information, comprehensive clinical characteristics, NYHA functional classification, and thorough echocardiographic evaluation. Operative data meticulously documented surgical techniques, bypass duration, and immediate perioperative complications. Postoperative follow-up was systematically conducted at predetermined intervals of 1, 3, 6, and 12 months, incorporating clinical assessment, echocardiographic evaluation, and documentation of adverse events.

2.5. Study Endpoints

Primary endpoints comprised operative mortality (defined as death occurring within 30 days of surgical intervention or during initial hospitalization) and quantifiable improvement in ventricular function. Secondary endpoints encompassed postoperative complications, changes in NYHA functional classification, and echocardiographic parameters including ventricular dimensions, ejection fraction quantification, and pulmonary artery pressure measurements.

2.6. Statistical Analysis

Continuous variables were expressed as mean ± standard deviation and analyzed using Student's t-test or Mann-Whitney U test as appropriate based on distribution characteristics. Categorical variables were presented as frequencies and percentages and analyzed using chi-square methodology or Fisher's exact test when expected frequencies fell below 5. Survival analysis employed Kaplan-Meier techniques, with inter-group differences evaluated through log-rank test application. Statistical significance was established at p<0.05. All analyses were performed using SPSS version 16.0 software (SPSS Inc., Chicago, IL, USA).

2.7. Ethical Approval

This investigation received approval from the Ethics Committee of Hue Central Hospital (approval number: 2335/BVH, January 10th, 2025). The study was conducted in accordance with Declaration of Helsinki principles. Written informed consent was obtained from all participants prior to inclusion.

3. Results

3.1. Baseline Characteristics and Operative Data

Our study encompassed 87 patients who underwent mechanical mitral valve replacement with posterior leaflet preservation, stratified into two cohorts based on left ventricular functional parameters. As delineated in Table 1, baseline characteristics demonstrated comparable distribution between groups, with the notable exception of ventricular dimensions. The reduced EF group (≤50%) comprised 38 patients (43.7%) who exhibited significantly augmented left ventricular dimensions and diminished ejection fraction compared to their counterparts in the preserved EF cohort.This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, as well as the experimental conclusions that can be drawn.

The operative data elucidated in Table 2 illustrates the successful preservation of the posterior leaflet apparatus in the preponderance of cases, with remarkably high preservation rates across all segments (P1: 88.5%, P2: 95.4%, P3: 92.0%). Mean cardiopulmonary bypass and cross-clamp durations were 82.3 ± 20.8 and 56.3 ± 15.9 minutes respectively, with no statistically significant inter-group variations. Early postoperative outcomes revealed impressively low complication rates, with hospital mortality of merely 2.3% (2 patients), reoperation for bleeding in 1.1%, and surgical site infection in 2.3%. The mean ventilation duration was 23.3 ± 51.1 hours, with the majority of patients (57.5%) achieving extubation within 12 hours.

3.2. Follow-up Outcomes and Survival Analysis

The compelling findings emerged from the 12-month follow-up data, meticulously presented in Table 3 and Figure 1. The reduced EF cohort demonstrated remarkable improvement in left ventricular function, with mean EF increasing substantially from 48.8 ± 5.2% preoperatively to 61.6 ± 7.2% (p<0.05). Left ventricular dimensions decreased significantly within this cohort, with LVEDd reducing from 59.2 ± 6.6 mm to 47.6 ± 4.0 mm (p<0.05). Both groups exhibited profound functional improvement, with all surviving patients achieving NYHA class I or II status at the 12-month assessment.

Survival analysis utilizing Kaplan-Meier curves demonstrated comparable outcomes between cohorts throughout the 12-month follow-up period (Figure 1). The overall survival rates at 12 months were 94.66% and 97.96% for reduced EF and preserved EF groups, respectively (log-rank test, p=0.42). Survival rates stabilized after the initial 6-month period in both cohorts, with the majority of adverse events occurring during the early postoperative phase. After the follow-up period, 34 of 38 patients (89.5%) in the reduced EF group and 45 of 49 patients (91.8%) in the preserved EF group remained engaged in active follow-up.

Throughout the follow-up period, no instances of prosthetic valve thrombosis or paravalvular leak were documented. Prosthetic valve functionality remained consistently optimal, with mean pressure gradients maintaining between 9.3 ± 3.4 mmHg and 10.4 ± 2.9 mmHg across the entirety of the follow-up duration. Analysis of freedom from valve-related complications revealed excellent outcomes in both cohorts, with no statistically significant differences between patients with reduced and preserved ejection fraction (p=0.86).

These comprehensive findings demonstrate that mechanical mitral valve replacement with posterior leaflet preservation can be implemented with exceptional safety and efficacy in patients with reduced left ventricular function, culminating in substantial improvements in cardiac performance and clinical status during the initial postoperative year. The pronounced enhancement in ventricular function observed within the reduced EF cohort is particularly remarkable, suggesting this sophisticated surgical approach may confer specific therapeutic advantages for patients with compromised ventricular performance. The comparable survival rates between cohorts further substantiate the safety profile of this surgical technique in this challenging patient population with reduced left ventricular function.

4. Discussion

Our investigation conclusively demonstrates that mechanical mitral valve replacement with posterior leaflet preservation can be implemented with remarkable safety and efficacy in patients presenting with reduced left ventricular function (EF ≤50%). Several significant findings have emerged from our comprehensive analysis.

Primarily, the substantial enhancement in left ventricular function—from a mean preoperative EF of 48.8% to 61.6% at 12 months—underscores the critical importance of preserving the subvalvular apparatus. This observation corresponds with Fukunaga and colleagues' research emphasizing that preserving anatomical and functional continuity between the mitral apparatus and ventricular wall is fundamental for optimal recovery, particularly in patients with compromised cardiac performance [15,16]. The magnitude of improvement in ejection fraction substantially exceeds that documented in conventional valve replacement series lacking preservation techniques [17].

Furthermore, our exceptionally low perioperative mortality rate compares advantageously with contemporary clinical series. Gao et al. demonstrated convincingly that MVR incorporating preservation techniques achieved acceptable mortality rates even among higher-risk patient cohorts [18]. This compelling evidence suggests that reduced ejection fraction should not be regarded as a prohibitive risk factor when appropriate preservation techniques are meticulously employed.

The marked reduction in left ventricular dimensions (LVEDD and LVESD) in our series provides robust evidence for positive ventricular remodeling. These findings substantiate recent mechanistic investigations by Coutinho et al. suggesting that preservation of the posterior leaflet facilitates the maintenance of physiological ventricular geometry and prevents progressive ventricular dilatation [11,19]. The improvement in ventricular dimensions was particularly pronounced among patients with reduced ejection fraction, suggesting this specific patient population may derive maximal therapeutic benefit from sophisticated preservation techniques.

Regarding technical considerations, we ascertained that meticulous attention to preserved leaflet tension is fundamental. As elegantly demonstrated by Guo et al., excessive tension or suboptimal preservation can significantly compromise the therapeutic benefits of this sophisticated technique [20]. Our standardized methodological approach to leaflet preservation, with particular emphasis on maintaining appropriate tissue tension whilst conscientiously avoiding excessive preservation that could potentially precipitate left ventricular outflow tract obstruction, undoubtedly contributed substantially to the exceptionally favorable outcomes observed [21].

The remarkable enhancement in functional status, with all surviving patients achieving NYHA functional class I or II at the 12-month assessment, is particularly significant in this challenging patient cohort. This profound clinical improvement correlates precisely with the echocardiographic evidence of enhanced ventricular performance and provides robust validation of the physiological benefits conferred by preservation techniques [22,23].

Our investigation exhibits several methodological limitations. The single-center nature and retrospective design may potentially restrict the broader generalisability of our findings. Additionally, extended longitudinal follow-up would be invaluable to comprehensively assess the durability of the observed improvements in ventricular function. Future investigations should consider incorporating more sophisticated imaging modalities to elucidate the precise mechanisms underlying ventricular recovery following the implementation of preservation techniques [24].

5. Conclusions

Our findings provide compelling evidence that mechanical mitral valve replacement incorporating posterior leaflet preservation represents a safe, effective, and highly advantageous surgical strategy for patients with compromised ventricular function. This technique facilitates significant improvement in both ventricular performance parameters and clinical outcomes during the initial postoperative year. These results strongly support prioritizing this surgical approach for this particularly high-risk patient population.